@ARTICLE{Blank97, title={Title}, journal={Journal of Geophysical Research}, volume={}, number={}, year={1997}, month={}, pages={0}, abstract={}, keywords={}, mynotes={UNREAD}, } @ARTICLE{Cornwall64, title={Scattering of Energetic Trapped Electrons by Very-Low-Frequency Waves}, journal={Journal of Geophysical Research}, volume={69}, number={}, year={1964}, month={}, pages={1251}, abstract={}, keywords={}, mynotes={UNREAD}, } @ARTICLE{Dungey63, title={Loss of Van Allen Electrons due to Whistlers}, journal={Planet. Space Sci.}, volume={11}, number={}, year={1963}, month={}, pages={591}, abstract={}, keywords={}, mynotes={UNREAD}, } @ARTICLE{May90, title={ Wave-Induced Particle Precipitation }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={52}, number={5}, year={1990}, month={May}, pages={}, abstract={ The following topics were dealt with: the roles of VLF and ULF waves in auroral particles acceleration, in multi-resonance proton interaction, and in remote sensing of lightning-induced electron precipitation }, keywords={ atmospheric elementary particle precipitation atmospherics ionosphere ionospheric electromagnetic wave propagation magnetosphere magnetospheric electromagnetic wave propagation wave-induced particle precipitation ionosphere wave-particle interactions magnetosphere VLF waves VLF subionospheric transmissions atmospheric Trimpi events auroral VLF hiss aeronomy ULF waves auroral particles acceleration multi-resonance proton interaction remote sensing lightning-induced electron precipitation }, mynotes={UNREAD}, }, @ARTICLE{AhmadDec86, title={ Low latitude discrete chorus emissions and very low frequency (VLF) hiss }, journal={Indian Journal of Physics, Part B}, volume={60B}, number={6}, year={1986}, month={Dec}, pages={501-7}, abstract={ Discrete chorus emissions observed at ground based low latitude stations at Nainital (19 degrees 02'N, 14.9 degrees 45'E, L equivalent to 1.16) and Varanasi (15 degrees 6'N, L equivalent to 1.07) and very low frequency (VLF) hiss recorded at Srinagar (24 degrees 26'N, 174 degrees 09'E, L equivalent to 1.28) have been explained by the electromagnetic ion cyclotron resonance process between the propagating wave and highly energetic charged particles. The resonant energies for various frequencies of the emissions have been computed from the expression of Stix (1962). The growth rates have been obtained by expression suggested by Misra and Tiwari (1977) for bi-Maxwellian distribution and found to be 3-5 rad, sec/sup -1/ indicating significant wave amplification }, keywords={ atmospheric radiation ionosphere magnetosphere low latitude discrete chorus emissions India very low frequency hiss biMaxwellian distribution ionosphere magnetosphere radiowave emission ground based low latitude stations Nainital Varanasi Srinagar electromagnetic ion cyclotron resonance process propagating wave highly energetic charged particles wave amplification }, mynotes={UNREAD}, }, @ARTICLE{AlpertJun80, author={Al'pert, Ya.L. and Moiseyev, B.S.}, title={ On the distribution of the field of electromagnetic waves emitted by a dipole in a homogeneous magnetoactive plasma }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={42}, number={6}, year={1980}, month={Jun}, pages={521-8}, abstract={ Deals with the emission of an electric dipole in a homogeneous magneto-active multicomponent plasma in all resonance frequency ranges omega which are lower than the Langmuir electron frequency omega /sub 0/. The authors show that the structure of the field represents two cones, one inserted into the other with the common symmetry axis along the vector of the magnetic field H/sub 0/. The surface of one of them corresponds to the plasma resonance region. The other is an analogue of Storey's cone in the whistler mode range. In the vicinity of the surfaces of these cones and near the symmetry axis, in a narrow range of angle, a considerable amplification of the field can take place. In some cases the maximum value of the field strength exceeds the field inside the cones, and the field of a similar dipole located in vacuum, by approximately (10/sup 1/-10/sup 5/) times. This effect is considerable and must play a prominent part in various processes taking place in a plasma }, keywords={ antenna radiation patterns antenna theory dipole antennas electromagnetic wave propagation in plasma whistlers homogeneous magnetoactive plasma plasma resonance whistler mode electromagnetic wave field EM wave emission dipole antennas radiowave radiation pattern }, mynotes={UNREAD}, }, @ARTICLE{AlpertMar80, title={ The direction of the group velocity of electromagnetic waves in a multicomponent magneto-active plasma in the frequency range 0< omega to infinity }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={42}, number={3}, year={1980}, month={Mar}, pages={205-16}, abstract={ The results of investigating the direction of the group velocity vector delta omega / delta K of all the branches of the electromagnetic waves existing in a cold magnetoactive plasma are given. Calculations are performed for the entire frequency range 040 keV in the range L approximately 2-3, consistent with theoretical predictions }, keywords={ atmospheric electron precipitation whistlers AD 1982 to 1983 VLF seasonal variation latitudinal variation diurnal distributions whistler-induced electron precipitation events subionospheric signal perturbations Trimpi events Palmer Siple Antarctica inner magnetospheric maximum burst precipitation activity }, mynotes={UNREAD}, }, @ARTICLE{ChanApr72, author={Chan, K.W. and Holzer, R.E. and Smith, E.J.}, title={ OGO-6 observation of whistlers }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={53}, number={4}, year={1972}, month={Apr}, pages={491}, abstract={ Wave normal vectors of fractional hop whistlers observed at various local times and latitudes have been studied throughout the OGO-6 altitude range 400 km to 1100 km. In general, the angle between the wave normal and the vertical becomes large at the higher altitudes. At low magnetic latitudes, the deviation is especially large. The latter phenomenon may be due to the horizontal electron density gradient associated with the equatorial anomaly in the electron density distribution. The local time effect, which may be caused by the different profiles of electron distribution in the upper ionosphere will be described }, keywords={ ionosphere whistlers wave normal vectors fractional hop whistlers 400 km to 1100 km low magnetic latitudes horizontal electron density gradient local time effect upper ionosphere OGO 6 observations }, mynotes={UNREAD}, }, @ARTICLE{ChmyrevSep90, author={Chmyrev, V.M. and Draganov, A.B. and Taranenko, Yu.N.}, title={ On the theory of whistler precursors on a VLF transmitter signal }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={52}, number={9}, year={1990}, month={Sep}, pages={797-800}, abstract={ A new type of whistler precursor found on a signal from the Siple VLF transmitter (Paschal, E.W. (1990) J. Geophys. Res. 95, 225) is explained in terms of spectral-choosing backscattering of whistlers by periodic plasma density striations created by counter-propagating transmitter signals in the magnetosphere. At signal amplitudes of 2 mV/m the density modulation is shown to be delta n/n/sub 0/=0.04%, corresponding to a coefficient of whistler backscattering, R= mod E/sub 2//E/sub 2/ mod =0.25. The same mechanism can be used to explain 'postcursor' occurrence, assuming that backscattering takes place also for a whistler reflected from the ionosphere during the second pass through the interaction region }, keywords={ whistlers postcursor radiowave propagation Antarctica theory whistler precursors VLF transmitter signal whistler precursor Siple spectral-choosing backscattering periodic plasma density striations counter-propagating transmitter signals magnetosphere mechanism }, mynotes={UNREAD}, }, @ARTICLE{ChmyrevMay91, author={Chmyrev, V.M. and Draganov, A.B. and Taranenko, Yu.N. and Teodosiev, D.}, title={ Acceleration of particles in the upper ionosphere and the magnetosphere due to decay interactions of whistlers. 1 }, journal={Physica Scripta}, volume={43}, number={5}, year={1991}, month={May}, pages={495-502}, abstract={ A numerical analysis of the three-wave decay interaction of oblique whistler mode waves with different types of ion waves is presented. It is shown that at altitudes h<2000 km the most effective mechanism is the decay interaction of whistlers with quasielectrostatic ion-cyclotron waves (the increment is Gamma approximately 25 s/sup -1/ for an initial whistler pump wave amplitude of E/sub 1//sup 0/=10 mV m/sup -1/) as well as with Alfven waves and ion-ion hybrid waves ( Gamma approximately 10 s/sup -1/ for the same pump amplitude E/sub 1//sup 0/). When taking into account the media inhomogeneity and the decay wave stabilization due to pump wave amplitude depletion, the magnitudes of excited ion waves are found to be E/sub 3/ approximately 50-120 mu V/(mHz/sup 1/2/) for E/sub 1//sup 0/=10 mV m/sup -1/. At such amplitudes parametrically excited ion waves can provide transverse ion acceleration with a rate of 0.5 eV s/sup -1/ and longitudinal electron acceleration up to 5 eV at a distance of the order of 2000 km, the flux reaching 3*10/sup 7/ el/(cm/sup 2/ sr eV) }, keywords={ ionosphere magnetosphere whistlers particle acceleration VLF upper ionosphere magnetosphere numerical analysis three-wave decay interaction oblique whistler mode waves ion waves quasielectrostatic ion-cyclotron waves Alfven waves ion-ion hybrid waves decay wave stabilization electron acceleration 2000 km }, mynotes={UNREAD}, }, @ARTICLE{ChurchOct83, author={Church, S.R. and Thorne, R.M.}, title={ On the origin of plasmaspheric hiss: ray path integrated amplification }, journal={Journal of Geophysical Research}, volume={88}, number={A10}, year={1983}, month={Oct}, pages={7941-57}, abstract={ An investigation has been made of processes responsible for the growth, damping, and propagation characteristics of whistler mode emissions within the Earth's plasmasphere. Three-dimensional ray path calculations of the integrated wave gain in a realistic model plasmasphere have provided an explicit confirmation of the anisotropic electron cyclotron resonant generation mechanism for the maintenance of plasmaspheric hiss. Peak wave amplification occurs for field-aligned waves in the outer plasmasphere. The majority of unstable low-frequency waves follow ray trajectories that internally reflect the plasmapause and are thus trapped within the plasmasphere. This reflection allows waves to subsequently propagate into the locally stable inner and middle plasmasphere and also migrate substantially in longitude. The combination of internal reflection at the plasmapause and magnetospheric reflection at high latitude provide an important class of wave trajectories that are recycled back to the equatorial growth region with sufficiently small wave normal angles to allow further cyclotron resonant amplification. It is unlikely that wave growth can occur from the natural incoherent emissivity level within the plasmasphere since the required gains ( approximately=100 dB) would mandate unreasonably high energetic electron flux. An alternate, as yet unidentified, embryonic source is therefore required to initiate the growth process }, keywords={ atmospheric radiation magnetosphere radiowave emission magnetosphere peak wave amplification origin plasmaspheric hiss ray path integrated amplification growth damping propagation whistler mode emissions electron cyclotron resonant generation mechanism }, mynotes={UNREAD}, }, @ARTICLE{ChustMay96, author={Chust, T. and Le Queau, D.}, title={ Resonant absorption of downward propagating electromagnetic hiss }, journal={Journal of Geophysical Research}, volume={101}, number={A5}, year={1996}, month={May}, pages={10695-710}, abstract={ EM hiss is regularly detected on low-altitude satellites at high magnetic latitudes. We solve the full wave equation for EM magnetosonic waves (MSWs) initially launched earthward at high altitudes above the satellite. Owing to both the inhomogeneity of the medium and the bi-ionic composition of the plasma, the wave field undergoes a singularity at the altitude where its frequency matches the local gyrofrequency of H/sup +/. This phenomenon is accompanied by strong modifications of the wave properties and by a resonant absorption that contributes to the heating of the protons. It is shown that a WKB point of view still provides a qualitative description of the full wave propagation. The resonant absorption can then be viewed as a three-step process as follows: (1) downward propagation of MSWs followed by (2) a reflection and by (3) a mode conversion into electromagnetic ion cyclotron waves, which are appropriate to heat the protons. During this process wave polarization reverses near the crossover point, where the mode conversion mainly occurs. The amplitude of the component B/sub perpendicular to / is found to undergo a moderate increase at the point where the wave frequency matches the proton gyrofrequency. The analysis is extended to include kinetic effects resulting from the longitudinal motions of the electrons T/sub e/. This aims at explaining the strong enhancement of the parallel electric field recorded onboard AUREOL 3. The estimate of the size of E/sub ¹¹/ (and of B/sub perpendicular to /) allows a precise diagnosis of the mode conversion of the incident electromagnetic hiss and therefore helps understanding how its energy is used to heat the protons }, keywords={ atmospherics magnetosphere magnetospheric electromagnetic wave propagation plasma waves resonant absorption downward propagating electromagnetic hiss EM magnetosonic waves singularity local gyrofrequency H/sup +/ downward propagation reflection mode conversion electromagnetic ion cyclotron waves wave polarization proton gyrofrequency electromagnetic hiss H }, mynotes={UNREAD}, }, @ARTICLE{ClilverdAug93a, author={Clilverd, M.A. and Clark, T.D.G. and Smith, A.J. and Thomson, N.R.}, title={ Observation of a decrease in mid-latitude whistler mode signal occurrence prior to geomagnetic storms }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={55}, number={10}, year={1993}, month={Aug}, pages={1479-85}, abstract={ VLF whistler mode signals received in 1986-1992 at Faraday, Antarctica (65 degrees S, 64 degrees W) and Dunedin, New Zealand (46 degrees S, 171 degrees E) show night-long decreases in occurrence which may be caused by changes in F-region absorption levels. The whistler mode occurrence normally decreases for one night and can only be detected during periods when whistler mode activity lasting several hours per night is usual. Decreases in occurrence are observed more often at Dunedin than at Faraday, probably due to long sub-ionospheric paths that result in weaker signals being received at Dunedin. The decreases in occurrence appear to be associated with solar disturbances and often occur a day before the onset of geomagnetic activity. Several of the events recur with a 27-day cycle that coincides with favourably placed solar coronal holes }, keywords={ ionospheric electromagnetic wave propagation magnetic storms radiowave propagation whistlers midlatitude whistler mode signal occurrence geomagnetic storm precursors VLF AD 1986 to 1992 Faraday Antarctica Dunedin New Zealand F-region absorption subionospheric paths solar disturbances geomagnetic activity solar coronal holes 27-day cycle ionosphere 21.4 to 24.8 kHz }, mynotes={UNREAD}, }, @ARTICLE{ClilverdJun96, author={Clilverd, M.A. and Thomson, N.R. and Smith, A.J.}, title={ Ducted whistler-mode signals received at two widely spaced locations }, journal={Annales Geophysicae}, volume={14}, number={6}, year={1996}, month={Jun}, pages={619-27}, abstract={ Whistler-mode signals from a single VLF transmitter that have propagated in the same duct, have been observed simultaneously at Faraday, Antarctica (65 degrees S, 64 degrees W) and Dunedin, New Zealand (46 degrees S, 171 degrees E). The signals received have group-delay times that differ in the order of 10 ms, which can be explained by the differences in southern-hemisphere sub-ionospheric propagation time from duct exit region to receiver for the two sites. This difference has been used to determine the location of the duct exit region, with confirmation provided by arrival-bearing information from both sites. The whistler-mode signals typically occur one or two days after geomagnetic activity, with K/sub p/>or=5. The sub-ionospheric-propagation model, LWPC, is used to estimate the whistler-mode power radiated from the duct exit region. These results are then combined with estimated loss values for ionospheric and ducted transmission to investigate the role of wave-particle amplification or absorption. On at least half of the events studied, plasmaspheric amplification of the signals appears to be needed to explain the observed whistler-mode signal strengths }, keywords={ ionosphere ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation radiowave propagation whistlers ionosphere whistlers VLF waves geomagnetic activity group delay time duct properties wave particle interaction receiver wave propagation transmitter amplification plasmasphere }, mynotes={UNREAD}, }, @ARTICLE{ClilverdJul95, author={Clilverd, M.A. and Thomson, N.R. and Smith, A.J.}, title={ The effect of the mid-latitude ionospheric trough on whistler mode ducting during magnetic storms }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={57}, number={8}, year={1995}, month={Jul}, pages={945-54}, abstract={ Whistler-mode signals observed at Faraday, Antarctica (65 degrees S, 64 degrees W, Lambda =50.8 degrees ) show anomalous changes in group delay and Doppler shift with time during the main phase of intense geomagnetic activity. These changes are interpreted as the effect of refracting signals into and out of ducts near L=2.5 by electron concentration gradients associated with edges of the mid-latitude ionospheric trough. The refraction region is observed to propagate equatorwards at velocities in the range 20-85 ms/sup -1/ during periods of high geomagnetic activity (K/sub p/>or=5), which is in good agreement with typical trough velocities. Model estimates of the time that the trough edges come into view from Faraday show a good correlation with the observed start times of the anomalous features. Whistler-mode signals observed at Dunedin, New Zealand (46 degrees S, 171 degrees E, Lambda =52.5 degrees ) that have propagated at an average L-shell of 2.2 ( Lambda =47.6 degrees ) do not show such trough-related changes in group delay. These observations are consistent with a lower occurrence of the trough at lower invariant latitudes }, keywords={ ionosphere magnetic storms magnetospheric electromagnetic wave propagation radiowave propagation whistlers mid-latitude ionospheric trough whistler mode ducting magnetic storms Faraday Antarctica group delay Doppler shift intense geomagnetic activity refracting signals electron concentration gradients velocities Dunedin New Zealand 20 to 85 m/s }, mynotes={UNREAD}, }, @ARTICLE{ClilverdAug93b, author={Clilverd, M.A. and Thomson, N.R. and Smith, A.J.}, title={ The influence of ionospheric absorption on mid-latitude whistler mode signal occurrence from VLF transmitters }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={55}, number={10}, year={1993}, month={Aug}, pages={1469-77}, abstract={ Whistler mode signals from VLF transmitters received at Faraday, Antarctica (65 degrees S, 64 degrees W) during 1986-1991 show an annual variation in the number of hours over which signals are observed, with a maximum in June and a minimum in December. The variation was larger at solar minimum than at maximum and can be understood in terms of changes in absorption of VLF signals in the D-region, where the high geographic latitude of Faraday plays an important role in producing low attitude levels during the austral winter. In contrast, very little such variation was observed at Dunedin, New Zealand (46 degrees S, 171 degrees E) in 1991. Nighttime whistler mode signals have start and end time trends that are consistent with the influence of F-region absorption. Increases in whistler mode occurrence appear to be associated with periods of high geomagnetic activity at solar maximum but not during solar minimum. A possible mechanism involving decreased F-region absorption is discussed }, keywords={ electromagnetic wave absorption ionospheric electromagnetic wave propagation radiowave propagation whistlers ionospheric absorption midlatitude whistler mode signal VLF transmitters Faraday Antarctica AD 1986 to 1991 annual variation D-region Dunedin New Zealand F-region absorption geomagnetic activity solar activity ionosphere 21.4 to 24.8 kHz }, mynotes={UNREAD}, }, @ARTICLE{ClilverdJul92, author={Clilverd, M.A. and Thomson, N.R. and Smith, A.J.}, title={ Observation of two preferred propagation paths for whistler mode VLF signals received at a nonconjugate location }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={54}, number={7-8}, year={1992}, month={Jul}, pages={1075-9}, abstract={ Whistler mode signals from NLK (24.8 kHz) were received at Dunedin, New Zealand during 1989-90. The arrival bearing of the signals shows a bimodal distribution which is consistent with the results of Allcock and McNeill (1966), who suggested the existence of two paths with less total transmission loss than other paths. PATH 1 signals (which have a duct entry region just south of Dunedin's conjugate) are observed at all times of the year, while PATH 2 signals (which have a duct entry region just south of the NLK transmitter) show an annual variation in occurrence with a maximum in May and a minimum in November which may be a consequence of horizontal ionospheric electron density gradients near the duct entry region. Similarly preferred paths have been observed at Faraday, Antarctica from the NSS transmitter }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation whistlers VLF nonconjugate radiowave propagation path AD 1989 AD 1990 direction season whistler mode VLF signals nonconjugate location NLK Dunedin New Zealand arrival bearing bimodal distribution transmission loss PATH 1 duct entry region PATH 2 annual variation occurrence horizontal ionospheric electron density gradients 24.8 kHz }, mynotes={UNREAD}, }, @ARTICLE{ColsonJul93, author={Colson, W.B. and Gately, B. and Caudle, D.L. and Sturgess, K.}, title={ Analogies between the free electron laser and whistler mode amplification in the ionosphere }, journal={Nucl. Instrum. Methods Phys. Res. A, Accel. Spectrom. Detect. Assoc. Equip.(Netherlands), Nuclear Instruments & Methods in Physics Research, Section A(Accelerators, Spectrometers, Detectors and Associated Equipment)}, volume={A331}, number={1-3}, year={1993}, month={Jul}, pages={522-6}, abstract={ Very low frequency (VLF) electromagnetic waves, called 'whistler waves', propagating along magnetic field lines in the magnetosphere can be amplified by energetic electrons spiraling around the field lines near the geomagnetic equator. The electron and whistler wave interaction can be described by a theoretical model much like that used for the free electron laser (FEL). The electron phase-space dynamics for both interactions is governed by the pendulum equation describing saturation, electron trapping, tapering and sensitivity to energy distributions }, keywords={ free electron lasers ionospheric electromagnetic wave propagation laser theory magnetospheric electromagnetic wave propagation whistlers laser theory very low frequency free electron laser whistler mode amplification ionosphere VLF electromagnetic waves whistler waves magnetic field lines magnetosphere energetic electrons geomagnetic equator electron phase-space dynamics pendulum equation saturation electron trapping tapering sensitivity energy distributions }, mynotes={UNREAD}, }, @ARTICLE{CoronitiDec94, author={Coroniti, F.V. and Greenstadt, E.W. and Moses, S.L. and Tsurutani, B.T. and Smith, E.J.}, title={ On the absence of plasma wave emissions and the magnetic field orientation in the distant magnetosheath }, journal={Geophysical Research Letters}, volume={21}, number={24}, year={1994}, month={Dec}, pages={2761-4}, abstract={ In early September, 1983 ISEE-3 made a long traversal of the distant dawnside magnetosheath starting near x=-150 R/sub E/ downstream. The distant magnetosheath often contains moderately intense plasma wave emissions at frequencies from several hundred Hz to 5 kHz. However, over time scales of many days, a clear correlation exists between the occurrence of the plasma waves and the cone angle ( theta /sub xB/) between the magnetic field and the plasma flow velocity (x-direction). For theta /sub xB/ large (small), the plasma wave amplitudes are near background (high). Sudden (<1 minute) changes in the local magnetic field orientation produce correspondingly sudden changes in the wave amplitudes. Statistically, the wave amplitudes decrease continuously with increasing theta /sub xB/ }, keywords={ magnetic fields magnetosphere plasma waves plasma wave emissions magnetosphere distant magnetosheath AD 1983 09 ISEE-3 distant dawnside magnetosheath cone angle magnetic field direction plasma flow velocity direction plasma wave amplitude changes local magnetic field orientation changes 178 Hz to 3.1 kHz }, mynotes={UNREAD}, }, @ARTICLE{CupermanApr74, author={Cuperman, S. and Sternlieb, A.}, title={ Obliquely propagating unstable whistler waves: a computer simulation }, journal={Journal of Plasma Physics}, volume={11}, number={}, year={1974}, month={Apr}, pages={175-88}, abstract={ Obliquely propagating unstable electron cyclotron electromagnetic (whistler) waves have been studied with the aid of an especially designed computer simulation experiment. The plasma-wave system considered is homogeneous and infinite, and the plasma is taken to be a mixture of warm (bi-maxwellian) and cold populations. With no cold plasma, the rates of growth of the low k modes maximize for the case of parallel propagation ( theta =0 degrees ) and decrease as theta increases; for higher k modes, the opposite occurs. Changing from k space to omega space the above results indicate that off-angle propagation tends to stabilize the low-frequency whistlers but to destabilize the higher-frequency ones. These results are consistent with linear predictions. In all cases, however, the total electromagnetic energy generated in the system decreases with increasing theta . When cold plasma is added to the system, the total generated electromagnetic energy can maximize for a non-zero propagation angle }, keywords={ computer aided analysis electromagnetic wave propagation in plasma plasma simulation whistlers obliquely propagating unstable whistler waves computer simulation cold plasma warm plasma electron cyclotron EM waves }, mynotes={UNREAD}, }, @ARTICLE{DaniellMar86, title={ Analytic properties of the whistler dispersion function }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={48}, number={3}, year={1986}, month={Mar}, pages={271-5}, abstract={ The analytic properties of the dispersion function of a whistler are investigated in the complex frequency plane. It possesses a pole and a branch point at a frequency equal to the minimum value of the electron gyrofrequency along the path of propagation. An integral equation relates the dispersion function to the distribution of magnetospheric electrons along the path and the solution of this equation is obtained. It is found that the electron density in the equatorial plane is very simply related to the dispersion function. A discussion of approximate formulae to represent the dispersion shows how particular terms can be related to attributes of the electron density distribution, and a new approximate formula is proposed }, keywords={ magnetospheric electromagnetic wave propagation whistlers magnetosphere EM wave propagation whistler dispersion function analytic properties complex frequency plane pole branch point electron gyrofrequency }, mynotes={UNREAD}, }, @ARTICLE{DatloweSep93, author={Datlowe, D.W. and Imhof, W.L.}, title={ Seasonal variations of energetic electron precipitation by cyclotron resonance with VLF waves from a ground-based transmitter }, journal={Radio Science}, volume={28}, number={5}, year={1993}, month={Sep}, pages={705-14}, abstract={ The authors report the detection of a seasonal variation in the occurrence of peaks in the spectra of energetic approximately 100-keV electrons precipitating from the inner radiation belt as the result of cyclotron resonance between waves and electrons. The spectra reported were observed from the low-altitude polar orbiting satellite P78-1 at midnight local time. The data, acquired over the 5-year period from March 1979 to July 1984, compose the first multiyear data set used to study cyclotron resonance peaks. The geographical distribution of the events is strongly clustered around the 22.3-kHz VLF transmitter NWC in Australia. Binning the data into seasons, the authors find that the events occur 2.5 times more often during the 6 months from day 80 to 263 than during the remainder of the year and that the seasonal difference is statistically significant at a high level. Since the observed change is in the frequency of occurrence of the peaks and not in the mean energy of the peaks, they attribute the effect to a seasonal change in ionospheric transmission of VLF waves rather than a seasonal change in the equatorial cold plasma density }, keywords={ atmospheric electron precipitation cyclotron resonance ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation plasma radiation belts radiowave propagation energetic electron precipitation cyclotron resonance VLF waves ground-based transmitter AD 1979 03 to 1984 07 seasonal variation inner radiation belt P78-1 satellite observations geographical distribution ionospheric transmission 22.3 kHz }, mynotes={UNREAD}, }, @ARTICLE{DavidsonNov87, author={Davidson, G.T. and Chiu, Y.T.}, title={ A nonlinear model of wave-particle interactions in the trapped radiation belts, auroral pulsation solutions }, journal={Geophysical Research Letters}, volume={14}, number={11}, year={1987}, month={Nov}, pages={1166-9}, abstract={ The interactions of waves and trapped electrons were described by a closed system of three nonlinear coupled equations. The model has applications to many aspects of wave-particle interactions in the magnetosphere. Nonlinear numerical solutions pertinent to auroral pulsations have been computed for realistic ranges of physical parameters. The results confirm that precipitation pulsations can be initiated by either an injection of energetic trapped particles or an increase in the plasma ionization density. Relaxation of the system results in cyclic phase trajectories about a (quasi-equilibrium) point that is not located at the initial equilibrium point. This observation may explain the tendency of auroral pulsations to appear superimposed upon an increase in the general rate of electron precipitation. The results also imply that precipitation pulsations are most readily initiated by an encounter of drifting energetic electrons with a region of enhanced cold plasma density }, keywords={ atmospheric electron precipitation atmospheric ionisation atmospherics aurora magnetosphere plasma radiation belts three-equation closed system plasma relaxation energetic trapped particles injection VLF atmospherics electron precipitation pulsations quasi-equilibrium point trapped particles density morningside aurora nonlinear model wave-particle interactions trapped radiation belts auroral pulsation solutions trapped electrons nonlinear coupled equations magnetosphere numerical solutions plasma ionization density cyclic phase trajectories initial equilibrium point drifting energetic electrons enhanced cold plasma density }, mynotes={UNREAD}, }, @ARTICLE{DavidsonApr86, title={ Pitch angle diffusion in morningside aurorae. I. The role of the loss cone in the formation of impulsive bursts of precipitation }, journal={Journal of Geophysical Research}, volume={91}, number={A4}, year={1986}, month={Apr}, pages={4413-27}, abstract={ Pitch angle diffusion of energetic electrons is important in morningside diffuse aurorae, equatorward of the auroral oval, where the plasma is shielded from the influence of large-scale electric fields. Morningside aurorae exhibit complex spatial and temporal structure. The temporal structure is addressed in a treatment which includes the principal elements of the feedback between pitch angle diffusion and VLE wave growth. A time-dependent bounce-average pitch angle diffusion equation is derived for the electron flux in and near the loss cone. The diffusion equation includes backscatter from the atmosphere. The atmospheric backscatter is represented by an empirical model in which the pitch angle distribution in the loss cone is approximated by a Taylor series in the sine of the pitch angle. The backscatter model is adjusted to match detailed computations performed with a Fokker-Planck code for the scattering and slowing of energetic electrons in the atmosphere }, keywords={ atmospheric electron precipitation magnetosphere electron precipitation ionosphere magnetosphere morningside loss cone formation impulsive bursts pitch angle diffusion VLE wave growth bounce-average pitch angle diffusion equation }, mynotes={UNREAD}, }, @ARTICLE{DavidsonAug75, title={ Finite temperature effects on the pitch angle diffusion of charged particles in the magnetosphere }, journal={Journal of Geophysical Research}, volume={80}, number={22}, year={1975}, month={Aug}, pages={3172-80}, abstract={ Resonance conditions and diffusion trajectories are developed for magnetospheric trapped particles interacting with whistler-type waves propagating along the magnetic field direction. The results are related to the plasma density and temperature. It is shown that finite temperature effects are insignificant for electrons interaction with right-handed whistler waves. For ions interacting with left-handed ion cyclotron waves the diffusion trajectories are found to deviate considerably from pure pitch angle diffusion for parallel energies less than the effective temperature. It is argued that pitch angle diffusion in the ring current is strongly inhibited at proton energies less than about 30 keV during strong storms and that an example of such behaviour may have been observed by instruments aboard the S/sup 3/ satellite. For electrons resonating with left-handed waves a minimum energy condition is derived, and wave growth rates are discussed for a beam of relativistic electrons injected into the magnetosphere. It is suggested that finite temperature effects could be invoked to modify the current theories of ring current precipitation }, keywords={ magnetosphere whistlers pitch angle diffusion charged particles magnetosphere diffusion trajectories trapped particles finite temperature effects ring current whistlers }, mynotes={UNREAD}, }, @ARTICLE{De95, author={De, B.K. and Sarkar, S.K.}, title={ Nighttime fading of VLF and LF atmospherics in relation to geomagnetic activity }, journal={Meteorology and Atmospheric Physics}, volume={55}, number={3-4}, year={1995}, month={}, pages={235-42}, abstract={ Long-period fading observed in recordings of VLF and LF atmospherics in meteorologically clear nights exhibits a good correlation with the geomagnetic activity index A/sub p/. The fading phenomenon occurs more frequently in the case of integrated field intensity of atmospherics than in the case of an LF radio signal transmitted from a certain station. The phenomenon has been analyzed for the monsoon and post-monsoon periods separately, and the results have been discussed in relation to the large-scale travelling ionospheric disturbances. The modal value of fade periods for VLF and LF atmospherics has been found to be about one hour. It is noted that the correlation of the fade amplitude of nighttime VLF and LF atmospherics versus the geomagnetic activity is frequency dependent and increases from VLF to LF }, keywords={ atmospherics fading ionospheric electromagnetic wave propagation magnetic storms radiowave propagation nighttime fading Calcutta VLF LF atmospherics geomagnetic activity clear nights geomagnetic activity index A/sub p/ integrated field intensity radio signal monsoon large-scale travelling ionospheric disturbances fade periods fade amplitude 40 kHz 9 kHz 27 kHz 81 kHz }, mynotes={UNREAD}, }, @ARTICLE{DelannoyJun86, author={Delannoy, C. and Lefeuvre, F.}, title={ MAXENTWDF-a computer program for the maximum entropy estimation of a wave distribution function }, journal={Computer Physics Communications}, volume={40}, number={2-3}, year={1986}, month={Jun}, pages={389-419}, abstract={ A random electromagnetic field can be described by a wave distribution function (WDF) that specifies how the wave energy density is distributed with respect to the angular frequency omega and to the wave normal direction K. Such a WDF is related to the values of the N auto and cross-power spectra of the field components by the set of integral equations: s/sub i/= integral /sub x1//sup x2/ integral /sub y1//sup y2/a/sub i/(x,y)G(x,y)dxdy, i=1, . . ., N, where G(x,y) is the WDF, defined as positive everywhere, a/sub i/(x,y) are known kernels, and S/sub i/ are N independent quantities derived from the power spectra. The authors find an estimation of G(x,y) from given a/sub i/(x,y) functions and from measured values s/sub i/ of the s/sub i/ using the MAXENTWDF program. The program package has been written in the Fortran IV language. It runs on a IBM 370/168 computer, and, with some minor modifications, on a CDC 7600 and a HP 1000. It has been used for the analysis of ELF and VLF emissions observed on board the satellite GEOS-1 }, keywords={ geophysics computing magnetospheric electromagnetic wave propagation artificial satellites MAXENTWDF computer program maximum entropy estimation wave distribution function wave energy density power spectra Fortran IV language ELF VLF GEOS-1 }, mynotes={UNREAD}, }, @ARTICLE{DentonNov96, author={Denton, R.E. and Anderson, B.J. and Ho, G. and Hamilton, D.C.}, title={ Effects of wave superposition on the polarization of electromagnetic ion cyclotron waves }, journal={Journal of Geophysical Research}, volume={101}, number={A11}, year={1996}, month={Nov}, pages={24869-85}, abstract={ Using data from the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer spacecraft, the authors make a detailed comparison between the observed polarization properties of electromagnetic ion cyclotron (EMIC) waves and those predicted by theory. The polarization can be described by three parameters: the ellipticity epsilon , the ratio of parallel (to the background magnetic field B/sub 0/) magnetic fluctuations delta B/sub z/ to the major axis component of the elliptical perturbation in the perpendicular plane delta B/sub major/, and the phase angle between delta B/sub z/ and delta B/sub major/. On the basis of the plasma parameters observed during EMIC events, the authors have calculated the linear properties of the theoretical modes and compared these to the observations. The result is that two and in some cases, three of the observed polarization properties are inconsistent with the assumption that the waves result from a single linear mode. They use a simple model with two constituent waves in various azimuthal orientations (around B/sub 0/) and temporal phase relations and show that the distribution of observed polarization properties can be understood as resulting from tile superposition of more than one mode. When there is superposition, the instantaneous polarization characteristics of the fluctuations do not reliably reflect the constituent wave properties and the minimum variance direction cannot be associated with a wave vector direction. Nonetheless, they have shown that the constituent wave properties can be inferred from the distribution of observed properties. For superposition of two waves with only slightly dissimilar characteristics, the constituent wave E is approximately the median observed E, E, and the constituent theta /sub kB/ (angle between the wave vector k and B/sub 0/) is approximately given by tan theta /sub kB/= delta B/sub z// delta B/sub major//E, with the overbar on delta B/sub z// delta B/sub major/ again indi }, keywords={ magnetosphere plasma waves magnetosphere plasma wave wave superposition polarization electromagnetic ion cyclotron wave EMIC EM ion cyclotron wave ellipticity AMPTE phase angle }, mynotes={UNREAD}, }, @ARTICLE{DevineSep95, author={Devine, P.E. and Chapman, S.C. and Eastwood, J.W.}, title={ One- and two-dimensional simulations of whistler mode waves in an anisotropic plasma }, journal={Journal of Geophysical Research}, volume={100}, number={A9}, year={1995}, month={Sep}, pages={17189-203}, abstract={ Presents results from self-consistent, one- and two-dimensional, electromagnetic simulations of the electron whistler mode instability relevant to the near-Earth nightside plasma sheet region during geomagnetically disturbed times. Specifically, the authors study the evolution of energetic, anisotropic (T/sub perpendicular to />T/sub ///) electron distributions that are injected into the nightside ring current region at geomagnetically disturbed times, the resulting growth of electron whistler mode waves, and subsequent electron pitch angle diffusion via electron whistler wave-particle interactions }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation plasma instability plasma simulation plasma waves electron whistler mode instability whistler mode waves anisotropic plasma 1D simulations 2D simulations EM simulations near-Earth nightside plasma sheet region geomagnetically disturbed times electron distributions nightside ring current region magnetosphere electron pitch angle diffusion electron whistler wave-particle interactions }, mynotes={UNREAD}, }, @ARTICLE{DudnikMay96, title={ Precipitating radiation belt electrons as a source of high-frequency radio emission }, journal={Radiat. Meas. (UK), Radiation Measurements}, volume={26}, number={3}, year={1996}, month={May}, pages={395-7}, abstract={ Estimations of spectral radiation density of the synchrotron radio-frequency emission of electrons precipitating from the Earth's radiation belts into the atmosphere during magnetic storms are performed. Calculation is made for some special distribution function of ultrarelativistic electrons, having a power energetic spectrum, sinusoidal pitch-angle distribution and Gaussian distribution of concentration in an equatorial plane. The calculated value of the spectral radiation density of high-frequency radiation is in satisfactory agreement with observed intensities of bursts of sporadic radio-frequency emissions in near-Earth space. The conclusion is made that the precipitating electron flux may be identified by a series of high-frequency radio emission bursts of the Earth's magnetosphere by the use of inexpensive and simple ground-based installations }, keywords={ atmospheric electron precipitation atmospheric radiation ionosphere magnetic storms radiation belts radiowave emission radiation belt electrons electron precipitation high-frequency radio emission HF radioemission spectral radiation density synchrotron radio-frequency emission magnetic storm ionosphere ultrarelativistic electrons sinusoidal pitch-angle distribution ionosphere magnetosphere interaction relativistic electron VHF }, mynotes={UNREAD}, }, @ARTICLE{DysonMay80, author={Dyson, P.L. and Bennett, J.A.}, title={ A universal chart for use in relating ionospheric absorption to phase path and group path }, journal={IEEE Transactions on Antennas and Propagation}, volume={AP-28}, number={3}, year={1980}, month={May}, pages={380-4}, abstract={ The absorption of a radio wave in the ionosphere can be approximated by A=( omega /c)(1/2) integral (Z( mu '- mu )/(1+g) cos alpha ds, where the integral is along the ray that exists when the normalized collision frequency Z=0. mu ' and mu are the group and phase refractive indices, respectively, and alpha the angle between the wave normal and-ray direction. Graphs are presented from which g can be obtained for any values of the ionospheric plasma parameters X and Y }, keywords={ electromagnetic wave absorption ionospheric electromagnetic wave propagation radiowave propagation ionospheric absorption phase path group path normalized collision frequency ionospheric plasma parameters radiowave absorption }, mynotes={UNREAD}, }, @ARTICLE{ElsenMar97, author={Elsen, R.K. and Winglee, R.M.}, title={ The average shape of the magnetopause: a comparison of three-dimensional global MHD and empirical models }, journal={Journal of Geophysical Research}, volume={102}, number={A3}, year={1997}, month={Mar}, pages={4799-819}, abstract={ The authors present a predictive model of the magnetopause, constructed using three-dimensional global MHD simulations of the magnetosphere over a range in solar wind dynamic pressure and the north-south component of the interplanetary magnetic field (IMF B/sub z/). The magnetopause, is identified in the simulations using electric current intensity, thermal pressure, and magnetic field line mapping. The magnetopause is fitted by least squares to an ellipse in each plane, and a fully three-dimensional magnetopause surface is constructed by assuming an elliptical cross section at intermediate clock angles. There is considerable flaring of the magnetopause dependent on B/sub z/ in the noon-midnight meridian plane due to reconnection but virtually no flaring in the equatorial plane. Despite this asymmetry, when averaged over clock angle, the model shows a general agreement with recent (axisymmetric) empirical magnetopause models and predicts observed magnetopause crossings with about the same accuracy as the empirical models. Unlike these empirical models, the authors' model can directly investigate asymmetries between the meridian and equatorial planes. The subsolar distance, directly measured from the simulations, varies linearly with B/sub z/ for both northward and southward interplanetary magnetic field, as do distances to the magnetopause on the flanks. Magnetospheric plasma pressure causes these distances to scale with dynamic pressure by a power law whose exponent is a bit less than -1/6 on the dayside, but little deviation from this ideal Chapman-Ferraro value is seen in the magnetotail. These uniform changes with B/sub z/ lead to approximate conservation of (1) magnetopause shape in the dayside equatorial plane?(2) projected area in the dayside meridian plane, and (3) magnetopause cross-sectional area in the dawn-dusk plane. The dawn-dusk magnetopause cross section is nearly circular on average, but cross sections in the tail are elongated in the Z direction on }, keywords={ magnetosphere magnetosphere average shape magnetopause three-dimensional model empirical model global MHD model morphology configuration predictive model solar wind dynamic pressure interplanetary magnetic field IMF direction electric current intensity thermal pressure magnetic field line mapping }, mynotes={UNREAD}, }, @ARTICLE{EtchetoJul85, author={Etcheto, J. and Christiansen, P.J. and Gough, M.P.}, title={ Problems in the interpretation of natural plasma wave spectra }, journal={Annales Geophysicae}, volume={3}, number={4}, year={1985}, month={Jul}, pages={417-20}, abstract={ Several mechanisms have been invoked to explain the origin of the so-called electromagnetic non-thermal continuum radiation, or terrestrial myriametric radiation. All of them hinge on wave-wave coupling or conversion, linear or not. Continuum radiation can under certain assumptions be used as a nonlocal diagnostic of the medium. To validate any of such interpretations requires a reliable identification of the various waves present in the source region and of their mode of propagation. The authors show on one example of GEOS-1 measurements how the use of active relaxation sounder measurements allows one to determine reliably the characteristic frequencies of the medium, in particular the plasma frequency }, keywords={ atmospheric radiation atmospheric techniques magnetosphere nonthermal continuum radiowave emission TMR magnetosphere plasmapause measurement technique electrostatic cyclotron harmonic radiation EM wave VLF natural plasma wave spectra terrestrial myriametric radiation relaxation sounder measurements }, mynotes={UNREAD}, }, @ARTICLE{FairfieldApr74, title={ Whistler waves observed upstream from collisionless shocks }, journal={Journal of Geophysical Research}, volume={79}, number={10}, year={1974}, month={Apr}, pages={1368-78}, abstract={ Waves in the frequency range 0.5-4. Hz have been studied in the region upstream of the Earth's bow shock with data from the flux-gate magnetic field experiment on Imp 6. Such waves are invariably detected adjacent to the shock, persisting upstream for intervals often less than a minute but occasionally of the order of many hours. Analysis of 150 examples of these waves ( Delta B/B approximately=0.2) during a 3-month interval indicates that propagation directions generally make angles of between 20 degrees and 40 degrees with the field direction. The waves as measured in the spacecraft frame of reference are either left- or right-hand-polarized with respect to the average field direction. The left-handed waves generally have lower frequencies than the right-handed waves, and the left-handed frequencies never exceed 2.5 Hz. The measured sense of polarization is found to depend on the propagation direction (or alternatively, the field direction) relative to the solar wind direction. Propagation-solar wind angles greater than approximately 40 degrees (or field angles greater than 55 degrees ) correspond to right-hand polarization, and smaller angles correspond to left-hand polarization. It is concluded that the observed waves are right-handed waves in the plasma frame of reference with wavelengths of approximately 100 km propagating upstream in the whistler mode. Doppler-shifting reduces the observed frequencies in the spacecraft frame and reverses the observed polarization for those waves propagating more directly upstream. Similar waves are seen ahead of some interplanetary shocks }, keywords={ magnetosphere shock waves whistlers whistler waves collisionless shocks earth's bow shock Imp 6 propagation directions sense of polarization interplanetary shocks 0.5 to 4 Hz upstream waves }, mynotes={UNREAD}, }, @CONFERENCE{Faith96, author={Faith, J. and Joe Huang and Kuo, S.P.}, title={ Chaotic precipitation of relativistic electrons driven by large amplitude whistler waves }, booktitle={IEEE Conference Record - Abstracts. 1996 IEEE International Conference onPlasma Science (Cat. No.96CH35939)}, volume={}, number={}, year={1996}, month={}, pages={92-3}, abstract={ Summary form only given. It has for some time been known that electrons trapped by Earth's magnetic field can precipitate along the geomagnetic field lines into the polar regions. Here the secondary ionizations caused by the electrons impacting into the ionosphere can perturb VLF signals propagating in the Earth-ionosphere waveguide. The correspondence of these precipitation events with the presence magnetospheric whistler waves has led to much study of the interaction of whistler waves with the magnetospheric plasma. Most theories have considered Doppler shifted gyroresonant interactions. However, due to the directional nature of these interactions, they are unable to explain the simultaneous observation of precipitation events in geomagnetically conjugate regions in both hemispheres. Therefore we will investigate the interaction on a single test electron with a large amplitude nonresonant wave. We show that the interaction of a whistler wave with a trapped bouncing electron can lead to chaos in the electron trajectory. The dynamics of the electron trajectory depend strongly on both particle energy and wave amplitude. In order to induce chaos with physically realistic wave amplitudes, the particle energy must be quite large, and thus relativistic effects are important. Inclusion of relativistic effects also has the effect of decreasing the required threshold wave field for the onset of chaos for a wide range of particle energies. The end result of chaotic behavior is to enhance the electron's axial kinetic energy, which decreases the particles pitch angel allowing it to be scattered into the mirror field loss cone }, keywords={ chaos Earth-ionosphere waveguide ionosphere magnetosphere magnetospheric electromagnetic wave propagation relativistic plasmas whistlers chaotic precipitation relativistic electrons large amplitude whistler waves Earth's magnetic field trapped electrons geomagnetic field lines polar regions secondary ionizations ionosphere VLF signals Earth-ionosphere waveguide magnetospheric whistler waves magnetospheric plasma Doppler shifted gyroresonant interactions geomagnetically conjugate regions single test electron chaotic electron trajectory particle energy wave amplitude relativistic effects electron's axial kinetic energy mirror field loss cone }, mynotes={UNREAD}, }, @ARTICLE{FaithFeb97, author={Faith, J. and Kuo, S. and Huang, J.}, title={ Electron precipitation caused by chaotic motion in the magnetosphere due to large-amplitude whistler waves }, journal={Journal of Geophysical Research}, volume={102}, number={A2}, year={1997}, month={Feb}, pages={2233-41}, abstract={ Energetic electrons in the radiation belts are trapped by the magnetic field and undergo bounce motion about the geomagnetic equator. When a large-amplitude whistler wave is present, the motion of the electrons becomes perturbed. It is shown that the nonlinear interaction due to the spatial dependence of the field quantities causes the motion of some of the trapped particles to become chaotic. This chaotic scattering does not have a directional preference and may therefore offer a plausible explanation of the simultaneous observation of the electron precipitation into the upper atmosphere at geomagnetically conjugate regions due to a single lightning flash [Burgess and Inan, 1990]. After simplifying the dipole configuration of the geomagnetic field, a Hamiltonian formulation is used to study the dynamics of a single, trapped electron on the L=3 shell, subjected to a large amplitude 13.7 kHz whistler wave. A canonical transformation is introduced to remove the time dependence from the test electron's Hamiltonian. The chaotic behavior of the electron motion is investigated with surface of section and Lyapunov exponent techniques. To show that this chaotic behavior can lead to particle precipitation, the temporal evolution of the equatorial pitch angle of the electron is computed. Considering electrons with an initial pitch angle of 88 degrees , the results are found to be qualitatively independent of the bounce frequency. They show that the equatorial pitch angle of a chaotic electron varies wildly and often dips below 25 degrees , the minimum loss cone angle one would expect to find for a charged particle in the magnetosphere. Therefore the electrons may escape the geomagnetic trap and precipitate }, keywords={ atmospheric electron precipitation chaos radiation belts whistlers electron precipitation chaotic motion magnetosphere large-amplitude whistler waves radiation belts bounce motion nonlinear interaction field quantities trapped particles chaotic scattering geomagnetically conjugate regions lightning flash dipole configuration Hamiltonian formulation L=3 shell canonical transformation time dependence surface of section Lyapunov exponent equatorial pitch angle 13.7 kHz }, mynotes={UNREAD}, }, @ARTICLE{Faith96, author={Faith, J. and Kuo, S.P. and Huang, J.}, title={ Chaotic electron motion driven by whistler waves in the magnetosphere }, journal={Comments on Plasma Physics and Controlled Fusion}, volume={17}, number={3}, year={1996}, month={}, pages={173-82}, abstract={ In the magnetosphere, energetic electrons are trapped by Earth's magnetic mirror field. It is shown that a large amplitude whistler wave can effectively perturb the electrons' trajectories. The nonlinear interaction due to the spatial dependence of the wave fields leads to chaos in the electron trajectories. This can diffuse electrons into the loss cone, and offers a possible explanation to the observed electron precipitation into the polar region of the ionosphere }, keywords={ chaos ionosphere magnetosphere magnetospheric electromagnetic wave propagation plasma transport processes radiation belts solar wind whistlers chaotic electron motion whistler waves magnetosphere energetic electrons magnetic mirror field large amplitude whistler wave nonlinear interaction spatial dependence wave fields chaos electron trajectories loss cone electron diffusion electron precipitation polar region ionosphere }, mynotes={UNREAD}, }, @ARTICLE{FarleyOct84, author={Farley, A.F. and Dowden, R.L.}, title={ Simultaneous satellite and ground observations of ducted and nonducted VLF emissions: generation region location and drift }, journal={Journal of Geophysical Research}, volume={89}, number={A10}, year={1984}, month={Oct}, pages={9133-8}, abstract={ Discrete emissions received on the satellite ISIS 2 on August 15, 1978, corresponded closely with the emissions received on nearby ground stations. Over the first part of the pass the signals were more or less simultaneous and identical in shape, but later they appear on the satellite record in a slightly more dispersed form with about a quarter of a second additional delay, strongly suggestive of nonducted travel from the emission region to the satellite. Ray tracing is used to attempt to reconstruct this event and establish the generation region of the emissions }, keywords={ atmospheric movements atmospheric radiation atmospherics magnetosphere magnetospheric electromagnetic wave propagation ducted VLF emissions VLF atmospherics AD 1978 08 15 magnetosphere EM wave propagation atmospheric movements VLF generation region location VLF generation region drift atmospheric radiation signal time delay reflected signal kHz 0005 satellite observations ground based observations Dunedin Campbell Island nonducted VLF emissions ISIS 2 August 15, 1978 }, mynotes={UNREAD}, }, @CONFERENCE{Fraser-Smith93, author={Fraser-Smith, A.C. and Turtle, J.P.}, title={ ELF/VLF radio noise measurements at high latitudes during solar particle events }, booktitle={ELF/VLF/LF Radio Propagation and Systems Aspects (AGARD-CP-529)}, volume={}, number={}, year={1993}, month={}, pages={16/8 pp.}, abstract={ The authors report simultaneous measurements of ELF/VLF radio noise (10 Hz-32 kHz) at (Thule and Sondrestromfjord, Greenland; and Arrival Heights, Antarctica) during a number of moderate and large solar particle events, including some of the largest observed during the last three decades. The results show major changes occurring in the Thule noise statistics following the start of the polar cap absorption and smaller changes at the other sites. The changes depend markedly on the frequency of the noise signals }, keywords={ atmospheric radiation electric noise measurement magnetospheric electromagnetic wave propagation radiowave propagation high latitudes ELF/VLF radio noise Greenland Antarctica solar particle events noise statistics polar cap absorption }, mynotes={UNREAD}, }, @ARTICLE{GanguliSep84, author={Ganguli, G. and Palmadesso, P. and Fedder, J.}, title={ Temporal evolution of whistler growth in a cold plasma injection experiment }, journal={Journal of Geophysical Research}, volume={89}, number={A9}, year={1984}, month={Sep}, pages={7351-5}, abstract={ Using a simple time dependent cold plasma density model and assuming a typical ambient radiation belt environment, the authors study the evolution of the whistler mode turbulence and particle precipitation in a cold plasma release experiment similar to one that may be conducted as part of the Active Magnetosphere Particle Tracer Explorers (AMPTE) program. It is known from earlier work that the release of cold lithium ions can significantly lower the critical energy E/sub c/ above which the resonant radiation belt electrons can pitch angle scatter. The authors study the time evolution of the one pass gain factor for a whistler wave packet and find that for parameters accessible to AMPTE type experiments the gain factor is large enough to ensure strong whistler turbulence and strong pitch angle diffusion of radiation belt particles }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation radiation belts solar wind whistlers magnetosphere EM wave Li ions plasma turbulence Earth solar wind ion injection experiment trapped particle whistler growth cold plasma injection experiment time dependent cold plasma density model radiation belt whistler mode turbulence particle precipitation strong pitch angle diffusion }, mynotes={UNREAD}, }, @ARTICLE{GendrinMay74, title={ Phase-bunching and other non-linear processes occurring in gyroresonant wave-particle interactions (in magnetosphere) }, journal={Astrophysics and Space Science}, volume={28}, number={1}, year={1974}, month={May}, pages={245-66}, abstract={ Considers the movement of individual electrons in a magnetized plasma in which a monochromatic wave is propagating in the whistler mode. Simple expressions are derived which give the displacement of the electrons as a function of time, the phase angle that their velocity vector makes with the magnetic component of the wave, their pitch angle and energy changes. A useful formula is obtained which gives the velocity range over which particles remain trapped inside the wave, as a function of the wave intensity and of the initial phase angle of the particle. It is shown that even strictly resonant particles can escape from the wave when their initial phase angle is very small. From the derived expressions, it is possible to compute the phase-bunching effect which occurs approximately at one trapping wavelength behind the leading edge of the interaction region. The total amount of energy which is taken from (or given to) the wave by magnetospheric electrons in both cases of naturally existing or artificially injected particles is also deduced. It is shown that these non-linear amplification processes can lead to very large VLF amplitude in the magnetosphere }, keywords={ atmospheric electromagnetic wave propagation electromagnetic wave propagation in plasma magnetosphere individual electrons magnetized plasma monochromatic wave whistler mode pitch angle energy changes magnetospheric electrons artificially injected particles VLF phase bunching nonlinear processes gyroresonant wave particle interactions }, mynotes={UNREAD}, }, @ARTICLE{GoldbergMar87, author={Goldberg, R.A. and Curtis, S.A. and Barcus, J.R.}, title={ Detailed spectral structure of magnetospheric electron bursts precipitated by lightning }, journal={Journal of Geophysical Research}, volume={92}, number={A3}, year={1987}, month={Mar}, pages={2505-13}, abstract={ The role of lightning as a VLF radio source for magnetospheric electron precipitation has been the subject of theoretical and experimental work. The authors present results from simultaneous measurements of the precipitating particles and the originating lightning source. These results clearly indicate the existence of an equational electron cyclotron resonance process (EECR) process but also reveal a second electron distribution from some other origin. The time-integrated energy flux from these latter identified precipitating electrons appears to be approximately equal in magnitude to that due to those identified with the EECR processes. EECR interactions are taken as referring to equatorial electron cyclotron resonance pitch angle scattering only. An additional possibility, though much less likely in the authors' opinion, is a second substantial component of pitch angle scattering via electron cyclotron resonance (ECR) occurring in off-equatorial locations (Chang and Inan, 1985). Finally, electron cyclotron resonance by nonducted waves has also been mentioned as a possible significant contributor to electron precipitation (e.g. Voss et al., 1984) }, keywords={ atmospheric electron precipitation lightning magnetosphere plasma plasma AD 1984 08 spectral structure magnetospheric electron bursts lightning VLF radio source electron precipitation equational electron cyclotron resonance process electron distribution time-integrated energy flux pitch angle scattering off-equatorial locations nonducted waves }, mynotes={UNREAD}, }, @ARTICLE{GoldbergMar83, author={Goldberg, R.A. and Curtis, S.A. and Barcus, J.R. and Siefring, C.L. and Kelley, M.C.}, title={ Controlled stimulation of magnetospheric electrons by radio waves: experimental model for lightning effects }, journal={Science}, volume={219}, number={4590}, year={1983}, month={Mar}, pages={1324-7}, abstract={ Magnetospheric electrons precipitated by ground-based coded very low frequency radio transmissions have been detected by rocket measurement of bremsstrahlung X-rays, caused by impact of the electrons with the upper atmosphere. The direct correlations obtained between the very low frequency signals and the X-rays demonstrate the limits of sensitivity required and indicate that this remote sensing technique would be useful for future study of very low frequency effects induced by single lightning strokes }, keywords={ atmospheric electron precipitation atmospheric radiation atmospherics bremsstrahlung ionospheric techniques lightning magnetosphere magnetospheric electromagnetic wave propagation remote sensing upper atmosphere magnetospheric electrons controlled precipitation ground based coded VLF radio transmissions atmospherics electrons upper atmosphere impact ionospheric techniques lightning broadband short duration VLF power fluxes kHz 0021.4 keV 0005 to 0080 AD 1982 06 23 to 07 07 radio waves lightning effects rocket measurement bremsstrahlung X-rays remote sensing technique single lightning strokes }, mynotes={UNREAD}, }, @ARTICLE{GorneyDec82, author={Gorney, D.J. and Church, S.R. and Mizera, P.F.}, title={ On ion harmonic structure in auroral zone waves: the effect on ion conic damping of auroral hiss }, journal={Journal of Geophysical Research}, volume={87}, number={A12}, year={1982}, month={Dec}, pages={10479-86}, abstract={ Several low-altitude auroral wave observations exhibiting ion harmonic frequency structure have been reported. Recent S3-3 wave and particle data are reported that illustrate examples of ion harmonic structure in auroral hiss and the associated energetic ion distributions. Such harmonic features have previously been attributed to either hot ion absorption or emission processes. The observed ionic conic distributions are modelled to evaluate their effect on auroral hiss near the lower hybrid resonance frequency where harmonic features are seen. The calculations indicate that resonant ion damping of auroral hiss can indeed account for this distinct class of observed harmonic feature }, keywords={ atmospheric radiation ionosphere magnetosphere ionosphere radiowave emission mechanism ionospheric noise VLF generation ion harmonic structure auroral zone waves ion conic damping auroral hiss }, mynotes={UNREAD}, }, @ARTICLE{GotselyukSep85, author={Gotselyuk, Yu.V. and Kuznetsov, S.N. and Kuznetsova, V.A. and Popelyavska, B. and Kimak, I. and Kudela, K.}, title={ Scattering of protons of the radiation belt on the whistler mode of VLF radiation }, journal={Kosmicheske Issledovaniya}, volume={23}, number={5}, year={1985}, month={Sep}, pages={729-35}, abstract={ Fluxes of quasitrapped protons with E/sub p/ approximately=1 MeV are recorded on the Interkosmos-5 Earth satellite at low altitudes in the region of L approximately=3-3.5 during the recovery phase of magnetic storms. The observed fluxes are explained by the scattering of protons of the radiation belt on the whistler mode of VLF radiation. The scattering mechanism is analyzed for quiet and magnetically disturbed times. The energies of protons interacting with the whistler mode of VLF radiation are given as a function of L. The scattering efficiency is compared with that for scattering due to other mechanisms }, keywords={ atmospheric proton precipitation atmospheric radiation atmospherics magnetic storms magnetosphere radiation belts whistlers quasitrapped protons fluxes wave-particle interactions low-altitude proton precipitation magnetosphere radiation belt protons scattering atmospherics proton energies high-latitude precipitation plasmasphere whistler mode VLF radiation Interkosmos-5 Earth satellite recovery phase magnetic storms scattering mechanism magnetically disturbed times scattering efficiency }, mynotes={UNREAD}, }, @ARTICLE{GrabbeFeb84, title={ A model for chorus associated electrostatic bursts }, journal={Journal of Geophysical Research}, volume={89}, number={A2}, year={1984}, month={Feb}, pages={919-23}, abstract={ The linear theory of the generation of electrostatic bursts of noise by electrons trapped in chorus wave packets is developed for a finite temperature electron beam and a Maxwellian electron and ion background. The growth rates determined are qualitatively in good agreement with those obtained by previous authors from a more idealized model. Two connected instability mechanisms seem to be occurring: a beam plasma (electron-ion two-stream) instability commonly associated with intensification of the chorus power levels, and a transitional or borderline resistive medium instability commonly associated with chorus hooks. The physical reasons for the two mechanisms is discussed }, keywords={ atmospheric radiation magnetosphere trapped particle radiowave emission VLF beam plasma instability magnetosphere model chorus associated electrostatic bursts linear theory generation noise electrons chorus wave packets electron beam growth rates instability mechanisms electron-ion two-stream borderline resistive medium instability }, mynotes={UNREAD}, }, @ARTICLE{GreenstadtJul92, author={Greenstadt, E.W. and Coroniti, F.V. and Moses, S.L. and Smith, E.J.}, title={ Plasma wave profiles of Earth's bow shock at low Mach numbers: ISEE 3 observations on the far flank }, journal={Journal of Geophysical Research}, volume={97}, number={A7}, year={1992}, month={Jul}, pages={10841-8}, abstract={ The Earth's bow shock is weak along its distant flanks where the projected component of solar wind velocity normal to the hyperboloidal surface is only a fraction of the total free stream velocity, severely reducing the local Mach number. The authors present a survey of selected crossings far downstream from the subsolar shock, delineating the overall plasma wave (pw) behavior of a selected set of nearly perpendicular crossings and another set of limited Mach number but broad geometry. The immediate upstream regions are included. The result is a generalizable pw signature, or signatures, of low Mach number shocks and some likely implications of those signatures for the weak shock's plasma physical processes on the flank }, keywords={ magnetosphere solar wind magnetosphere solar wind planet interaction AD 1982 AD 1983 bow shock low Mach numbers far flank crossings downstream plasma wave }, mynotes={UNREAD}, }, @ARTICLE{GreenstadtJun82, author={Greenstadt, E.W. and Scarf, F.L. and Kennel, C.F. and Smith, E.J. and Fredricks, R.W.}, title={ Plasma wave levels and IMF orientations preceding observations of interplanetary shocks by ISEE-3 }, journal={Geophysical Research Letters}, volume={9}, number={6}, year={1982}, month={Jun}, pages={668-71}, abstract={ Some interplanetary shocks detected by ISEE-3 are preceded by many hours of strongly-enhanced plasma wave noise at a few kHz, while others have essentially no wave precursors above background. It has been shown that these extremes correspond to quasi-parallel and quasi-perpendicular shocks, respectively, based on the instantaneous orientation angle theta /sub Bn/ of the interplanetary magnetic field (IMF) to the shock normal at the time the shocks cross the spacecraft. The authors show that precursor wave noise level is correlated with field orientation and an extrapolated theta /sub Bn/ throughout the preshock observation interval for two contrasting active and quiet cases, and that intermediate, variable noise levels correspond to intermediate, variable noise levels correspond to intermediate, variable IMF orientations. Foreshocks are inferred to be an intrinsic part of the structure of quasi-parallel interplanetary shocks }, keywords={ solar wind solar wind shock wave VLF ELF IMF orientation radiowave emission preceding strongly-enhanced plasma wave noise interplanetary magnetic field preshock }, mynotes={UNREAD}, }, @ARTICLE{Gurevich, title={ Ducting of electromagnetic waves in weak waveguides in the ionosphere and magnetosphere }, journal={Geomagnetizm i Aeronomiya}, volume={}, number={}, year={}, month={}, pages={}, abstract={ The simplest geometrical-optics and wave equations are obtained that describe the ducting of electromagnetic waves in ducts formed by weak elongated inhomogeneities. The propagation of short radio waves in magnetospheric waveguides is investigated. The conditions under which magnetospheric ducts exist are determined }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation radiowave propagation electromagnetic waves weak waveguides ionosphere magnetosphere geometrical-optics wave equations elongated inhomogeneities radio waves duct EM wave propagation }, mynotes={UNREAD}, }, @ARTICLE{GurnettNov88, author={Gurnett, D.A. and Calvert, W. and Huff, R.L. and Jones, D. and Sugiura, M.}, title={ The polarization of escaping terrestrial continuum radiation }, journal={Journal of Geophysical Research}, volume={93}, number={A11}, year={1988}, month={Nov}, pages={12817-25}, abstract={ Plasma wave measurements from the DE 1 spacecraft are used to determine the polarization of an escaping terrestrial continuum radiation event that occurred on March 2, 1982. The source of the radiation was determined by direction finding to be located near the magnetic equator on the nightside of the Earth at a radial distance of about 2.8-3.5 R/sub E/. The radiation was emitted in two meridional beams, one north and the other south of the magnetic equator. Polarization measurements using the two orthogonal electric antennas on DE 1 show that the radiation is right-hand polarized with respect to an outward directed E plane normal in the northern hemisphere and left-hand polarized in the southern hemisphere. Both the northern and southern hemisphere beams are propagating in the L-O mode at the spacecraft. The mode of propagation has also been confirmed using measurements of the E plane normal angle and ellipse ratio. This radiation is produced by coupling from intense upper hybrid resonance emissions near the plasmapause }, keywords={ atmospheric radiation magnetosphere kilometric AD 1982 03 02 magnetosphere radiowave emission plasma wave polarization escaping terrestrial continuum radiation nightside meridional beams L-O mode propagation intense upper hybrid resonance emissions plasmapause 30 to 100 kHz 2.8 to 3.5 Earthradii }, mynotes={UNREAD}, }, @ARTICLE{GurnettJul95, title={ On a remarkable similarity between the propagation of whistlers and the bow wave of a ship }, journal={Geophysical Research Letters}, volume={22}, number={14}, year={1995}, month={Jul}, pages={1865-8}, abstract={ It is well known that lightning-generated whistlers propagate along the Earth's magnetic field lines within a cone that at low frequencies makes an angle of 19 degrees 28' with respect to the local magnetic field. This angle turns out to be exactly the same as the half-angle of the bow wave of a ship in deep water. Both problems are complicated by the fact that the wave propagation is dispersive. The author shows that these two seemingly unrelated problems can be understood using the same basic approach, which is to analyze the direction of the group velocity as a function of the wave normal angle. This approach may have applications to other problems of geophysical interest, such as the flow wave generated by the interaction of a large object with a moving plasma }, keywords={ geophysical fluid dynamics magnetospheric electromagnetic wave propagation ocean waves surface waves (fluid) waves whistlers wave theory geophysical fluid dynamics magnetosphere radiowave propagation propagation whistler ship bow wave ocean wave sea surface gravity wave cone angle group velocity direction dispersive wave normal angle }, mynotes={UNREAD}, }, @ARTICLE{HansenJan90, author={Hansen, H.J. and Scourfield, M.W.J.}, title={ Associated ground-based observations of optical aurorae and discrete whistler waves }, journal={Journal of Geophysical Research}, volume={95}, number={A1}, year={1990}, month={Jan}, pages={233-9}, abstract={ Discrete VLF wave emissions in association with auroral light intensity fluctuations have been recorded at L=4. The correlated wave-particle interaction events are typical examples of the electron cyclotron resonance process responsible for the precipitation of energetic electrons in the vicinity of the plasmapause. The range of delay times between the correlated VLF wave and the optical signals, coupled with the frequency versus time characteristics of the VLF wave emissions, is consistent with the electron cyclotron source region being randomly located within 8000 km of the equatorial plane. The events are triggered by ducted whistler mode waves that originate from the opposite hemisphere to that of the station at which the observations are made. Events characterized by VLF waves of rising tone are presumed to occur in a region of enhanced plasma density commonly observed within the plasma trough. This region is probably responsible for ducting the VLF waves from the source to ground }, keywords={ atmospheric electron precipitation atmospherics aurora guided electromagnetic wave propagation magnetospheric electromagnetic wave propagation whistlers whistler waves amplification Sanae Antarctica VLF waves frequency-time characteristics VLF waves-optical signals delay time VLF waves ducting VLF waves dynamic spectra rising tone VLF waves ELF enhanced plasma density region pulsating aurora ground-based observations optical aurorae discrete whistler waves VLF wave emissions auroral light intensity fluctuations wave-particle interaction events electron cyclotron resonance plasmapause electron cyclotron source region equatorial plane ducted whistler mode waves plasma trough 0 to 4 kHz 720 ms }, mynotes={UNREAD}, }, @ARTICLE{HansenAug89, author={Hansen, H.J. and Scourfield, M.W.J.}, title={ Whistler duct dimensions from TV auroral images }, journal={Planetary and Space Science}, volume={37}, number={8}, year={1989}, month={Aug}, pages={979-85}, abstract={ Whistler mode VLF radiation propagates between opposite hemispheres of the Earth in field aligned ducts of enhanced plasma density. Despite the fact that whistler theory is firmly based on the existence of such ducts, there is little knowledge of their cross-sectional size or shape. Mid-latitude (L=4) ground based observations from Sanae, Antarctica, of ionospheric auroral optical emissions (imaged on a low-light level TV system) are observed in association with VLF radio emissions (recorded on a broadband VLF receiver). These optical emissions are interpreted as arising from electrons which interact with ducted VLF radiation via the electron cyclotron interaction. These observations provide estimates of 100 km by 400 km for whistler duct cross-sections in the equatorial plane }, keywords={ atmospheric electron precipitation atmospheric ionisation atmospheric structure aurora guided electromagnetic wave propagation magnetosphere magnetospheric electromagnetic wave propagation plasma whistlers magnetosphere whistler ducts dimensions whistler mode VLF radiation propagation wave-particle interactions electron precipitation electrons-whistlers interaction TV auroral images field aligned ducts enhanced plasma density cross-sectional size ground based observations Sanae Antarctica ionospheric auroral optical emissions low-light level TV system VLF radio emissions electron cyclotron interaction whistler duct cross-sections equatorial plane 100 to 400 km }, mynotes={UNREAD}, }, @ARTICLE{HansenNov83, author={Hansen, H.J. and Scourfield, M.W.J. and Rash, J.P.S.}, title={ Whistler duct lifetimes }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={45}, number={11}, year={1983}, month={Nov}, pages={789-94}, abstract={ Whistler data recorded during a 3h period at Sanae (L=3.98) and Halley (L=4.24) have been used to determine the lifetime of whistler ducts. Duct lifetimes as short as 30 min have been observed, a result which has important implications for current theories of ducts }, keywords={ magnetospheric electromagnetic wave propagation whistlers duration whistlers ducted propagation magnetosphere EM wave AD 1976 07 11 duct lifetimes lifetime whistler ducts }, mynotes={UNREAD}, }, @ARTICLE{HashimotoSep77, author={Hashimoto, K. and Kimura, I. and Kumagai, H.}, title={ Estimation of electron temperature by VLF waves propagating in directions near the resonance cone }, journal={Planetary and Space Science}, volume={25}, number={9}, year={1977}, month={Sep}, pages={871-7}, abstract={ A ray tracing computer program for non-ducted whistler mode waves in a warm plasma in the magnetosphere is developed, where electron temperature effects are taken into account. The refractive index is calculated from the warm-plasma approximation and is used in the ray tracing after its accuracy has been checked by comparison with the hot-plasma solution without approximation. The ray paths do not depend appreciably on electron temperature. However, there are regions where the waves are heavily damped by Landau damping. By paying attention to this damping region, the electron temperature can be estimated from a satellite observation of the Doppler shift and damping of a ground-based VLF signal }, keywords={ atmospheric techniques atmospheric temperature electromagnetic wave propagation in plasma magnetosphere magnetospheric electromagnetic wave propagation plasma whistlers ray tracing computer program warm plasma magnetosphere Landau damping electron temperature estimation waves refractive index nonducted whistler mode waves VLF waves propagation }, mynotes={UNREAD}, }, @ARTICLE{HashimotoFeb91, author={Hashimoto, K. and Nagano, I. and Okada, T. and Yamamoto, M. and Kimura, I.}, title={ Antenna vector impedance measurement by the EXOS-D (Akebono) very low frequency plasma wave instrument (VLF) }, journal={Geophysical Research Letters}, volume={18}, number={2}, year={1991}, month={Feb}, pages={313-16}, abstract={ Antenna impedance has been measured on board the EXOS-D (Akebono) satellite by imposing a constant current at VLF. The impedance is obtained in a complex form, i.e., as a resistance and a capacitance. This is essential to obtain the absolute electric field intensities of the VLF waves. A critical frequency below which the resistive part becomes important is also obtained }, keywords={ atmospheric techniques magnetosphere VLF antenna vector impedance measurement measurement technique very low frequency plasma wave instrument EXOS-D electric field }, mynotes={UNREAD}, }, @ARTICLE{HashimotoMar97, author={Hashimoto, K. and Nagano, I. and Yamamoto, M. and Okada, T. and Kimura, I. and Matsumoto, H. and Oki, H.}, title={ EXOS-D (AKEBONO) very low frequency plasma wave instruments (VLF) }, journal={IEEE Transactions on Geoscience and Remote Sensing}, volume={35}, number={2}, year={1997}, month={Mar}, pages={278-86}, abstract={ The Akebono (EXOS-D) satellite has been successfully observing the Earth's magnetosphere since it was launched on February 21, 1989. The objectives of VLF instruments on board the satellite were to investigate the behavior of plasma waves associated with accelerated auroral particles, wave-particle interaction mechanisms, and propagation characteristics of whistler-mode waves in the magnetosphere. The instruments measured not only the dynamic spectra of VLF waves up to 15 kHz by a wideband receiver, but also their absolute field intensities, wave normal vectors, and Poynting vectors. Two electric and three magnetic components with a bandwidth of about 50 Hz up to 12.5 kHz are sent to measure the wave normal vectors and Poynting vectors. The antenna impedance is measured to determine the correct absolute electric field intensities. The instruments have successfully measured the wave spectra, the wave normal vectors. Poynting vectors, the precise wave intensities, the antenna impedance, etc. The present paper describes the unique features of the instruments, especially the Poynting flux analyzers in more detail. Obtained scientific results are also reviewed }, keywords={ artificial satellites atmospheric measuring apparatus atmospheric techniques magnetosphere plasma diagnostics plasma waves measurement technique radiowave sounding EXOS-D AKEBONO very low frequency plasma wave instrument VLF apparatus equipment wave-particle interaction mechanism whistler-mode wave magnetosphere wave normal vector Poynting vector intensity }, mynotes={UNREAD}, }, @CONFERENCE{Hattori89, author={Hattori, K. and Hayakawa, M. and Shimakura, S. and Parrot, M. and Lefeuvre, F.}, title={ On the observation and generation mechanism of hiss-triggered chorus in the outer magnetosphere }, booktitle={ISAP Japan 1989. Proceedings of the 1989 International Symposium onAntennas and Propagation}, volume={}, number={}, year={1989}, month={}, pages={481-4 vol.2}, abstract={ The characteristics of VLF/ELF hiss-triggered chorus in the outer magnetosphere have been investigated on the basis of the detailed analyses of wave spectra, direction finding results and the fine structures of the hiss band. Their generation mechanism is also presented }, keywords={ atmospherics magnetosphere magnetospheric electromagnetic wave propagation radiowave propagation VLF ELF observation generation mechanism hiss-triggered chorus outer magnetosphere wave spectra direction finding results fine structures hiss band }, mynotes={UNREAD}, }, @CONFERENCE{Hayakawa94, author={Hayakawa, M. and Yamaguchi, M.}, title={ A new direction finding method for magnetospheric VLF/ELF radio waves }, booktitle={1994 International Symposium on Electromagnetic Compatibility (IEEE Cat.No.94TH0680-9)}, volume={}, number={}, year={1994}, month={}, pages={713-16}, abstract={ A new ground-based direction finding method based on the wave distribution function (WDF) reconstruction with use of the linear regularization of Phillips (1962) and Tikhonov (1965) type is proposed with emphasis on the optimization by means of the generalized cross validation (GCV). The results of numerical simulations indicate the effectiveness of the proposed method }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation radio direction-finding radiowave propagation statistical analysis magnetospheric VLF/ELF radio waves ground-based direction finding method wave distribution function linear regularization optimization generalized cross validation simulations numerical simulations radiowave propagation }, mynotes={UNREAD}, }, @ARTICLE{HayakawaJan90, author={Hayakawa, M. and Hattori, K. and Shimakura, S. and Parrot, M. and Lefeuvre, F.}, title={ Direction finding of chorus emissions in the outer magnetosphere and their generation and propagation }, journal={Planetary and Space Science}, volume={38}, number={1}, year={1990}, month={Jan}, pages={135-43}, abstract={ The GEOS 1 satellite wave data have been used to determine the wave normal directions of chorus emissions in the off-equatorial region (geomagnetic latitude approximately 17 degrees ) of the outer magnetosphere based on the direction finding of the wave distribution function method. The local time and L shell of the data analysed are L.T. equivalent to 10 h and L approximately 7.60, respectively, and only one event is extensively studied. There are two frequency bands of emissions; one above and the other below one half the electron gyrofrequency, but the latter is the dominant emission and is investigated. Two types of chorus are dealt with; rising tones and impulsive ones. About 90% of chorus emissions analysed are found to be composed of a single plane wave, which is in contrast to plasmaspheric hiss. There is no conspicuous relationship between theta (the angle of wave normal direction with respect to the Earth's magnetic field) and frequency for rising tones, and their theta s take larger values in a range of 30-55 degrees , whereas a tendency seems to appear, for an impulsive chorus, for waves at higher frequencies to travel at a larger angle to the field }, keywords={ atmospheric radiation magnetosphere radiowave emission radioemission rising tone chorus chorus emissions outer magnetosphere generation propagation wave normal directions impulsive }, mynotes={UNREAD}, }, @ARTICLE{HayakawaJan86, author={Hayakawa, M. and Ohmi, N. and Parrot, M. and Lefeuvre, F.}, title={ Direction finding of ELF hiss emissions in a detached plasma region of the magnetosphere }, journal={Journal of Geophysical Research}, volume={91}, number={A1}, year={1986}, month={Jan}, pages={135-41}, abstract={ Wave normal directions and wave distribution functions of ELF hiss emissions in a detached plasma region of the magnetosphere are determined, using data from the geostationary satellite GEOS 2 located in the equatorial plane at L=6.6. Three different methods of direction finding are utilized: Means's method based on the hypothesis of a single plane wave; the maximum likelihood method, assuming a few plane waves; and the maximum entropy method of determining the wave distribution function. From analyses of two equatorial ELF hiss events it is found that the wave distribution function is composed of a single peak and that the wave normals of the ELF hiss originating in the detached plasma region make very small angles with the Earth's magnetic field. The angular width of the unstable cone of the emissions is estimated. It is concluded that all the characteristics are consistent with the electron cyclotron instability }, keywords={ atmospherics magnetosphere plasma plasma instability ELF atmospherics DP hiss wave normal directions single plane wave hypothesis few plane waves hypothesis field-aligned wave normals unstable emission cone single-peak distribution function AD 1979 12 19 medium-energy electrons ELF hiss emissions detached plasma region magnetosphere wave distribution functions geostationary satellite GEOS 2 direction finding Means's method maximum likelihood method maximum entropy method equatorial ELF hiss events Earth's magnetic field electron cyclotron instability }, mynotes={UNREAD}, }, @CONFERENCE{Hayakawa89, author={Hayakawa, M. and Ohta, K. and Shimakura, S. and Xu, J.S.}, title={ Spaced direction-finding measurements of very low latitude whistlers and their propagation mechanism }, booktitle={ISAP Japan 1989. Proceedings of the 1989 International Symposium onAntennas and Propagation}, volume={}, number={}, year={1989}, month={}, pages={747-50 vol.3}, abstract={ Whistlers are the VLF electromagnetic waves which propagate through the magnetosphere after originating in the lightning discharges in the opposite hemisphere, and so they have been utilized as a useful tool of studying the dynamics and structure of the magnetosphere (Helliwell, 1965). The authors have carried out spaced direction-finding measurements of low- and equatorial-latitude whistlers in South China, and this paper presents the observing system, analysis system (direction-finding), observational facts and a discussion on the propagation mechanism }, keywords={ atmospheric techniques magnetospheric electromagnetic wave propagation radio direction-finding radiowave propagation whistlers radiowave propagation direction-finding very low latitude whistlers propagation mechanism VLF electromagnetic waves magnetosphere South China observing system }, mynotes={UNREAD}, }, @ARTICLE{HayakawaJul86, author={Hayakawa, M. and Parrot, M. and Lefeuvre, F.}, title={ The wave normals of ELF hiss emissions observed onboard GEOS 1 at the equatorial and off-equatorial regions of the plasmasphere }, journal={Journal of Geophysical Research}, volume={91}, number={A7}, year={1986}, month={Jul}, pages={7989-99}, abstract={ Three equatorial events have been analyzed, and it is found that just inside the plasmapause, the wave normal theta of ELF hiss is nearly aligned with the magnetic field, and when the observing position is 0.3-0.5 R/sub E/ inside from the plasmapause, there are two different groups of wave normal angles; one is a medium wave normal angle ranging from 20 degrees to 60 degrees and the other is large wave normal in a range from 70 degrees to 80 degrees , slightly smaller than the Gendrin angle. Then, off-equatorial observations have been made at geomagnetic latitudes 30 degrees to 24 degrees for L=4.66 to 2.90 inside the plasmasphere. The waves are always composed of two plane waves; both main and secondary peaks take very large wave normal angles, theta =80 degrees -85 degrees . The present direction finding results of equatorial ELF hiss have been extensively compared with the previous theoretical model to discuss the generation mechanism of plasmaspheric ELF hiss }, keywords={ atmospheric radiation ionosphere magnetosphere wave normal magnetosphere AD 1977 wave normals ELF hiss emissions plasmasphere generation mechanism }, mynotes={UNREAD}, }, @ARTICLE{HayakawaMar92, author={Hayakawa, M. and Shimakura, S. and Moriizumi, M. and Ohta, K.}, title={ On the location of causative atmospherics of very low latitude whistlers and their magnetospheric propagation mechanism }, journal={Radio Science}, volume={27}, number={2}, year={1992}, month={Mar}, pages={335-9}, abstract={ The purpose of the paper is to locate the causative atmospherics of very low latitude whistlers whose ionospheric exit regions have previously been determined at geomagnetic latitudes 10 degrees -13 degrees , in order to aid in understanding their magnetospheric propagation mechanism. It is found that the causative atmospherics of very low latitude whistlers are very widely distributed in a range from 500 to approximately 2500 km from the conjugate points of the ionospheric exit regions. This fact lends further support to the suggestion previous implication that preferred magnetospheric paths supporting field-aligned propagation are extremely rare in occurrence and that there exists a preferred and stable magnetospheric path in a very restricted location on days of high whistler activity }, keywords={ atmospherics guided electromagnetic wave propagation lightning magnetosphere magnetospheric electromagnetic wave propagation whistlers causative atmospherics location AD 1988 01 05 to 11 thunderclouds complexes locations lightning flashes geomagnetic latitudes 10 degrees to 13 degrees VLF whistlers ELF whistlers conjugate points distances S China Indonesia E Asia SE Asia very low latitude whistlers magnetospheric propagation mechanism ionospheric exit regions conjugate points preferred magnetospheric paths field-aligned propagation stable magnetospheric path 0.5 to 2.5 Mm 2 to 6 kHz }, mynotes={UNREAD}, }, @CONFERENCE{Hayakawa92, author={Hayakawa, M. and Shimakura, S. and Shimizu, M. and Hattori, K. and Iwama, N.}, title={ Direction finding of magnetospheric VLF/ELF waves based on the simultaneous measurement of multiple field components }, booktitle={IEEE Antennas and Propagation Society International Symposium. 1992 Digest.Held in Conjuction with: URSI Radio Science Meeting and Nuclear EMP Meeting(Cat. No.92CH3178-1)}, volume={}, number={}, year={1992}, month={}, pages={234-7 vol.1}, abstract={ The authors report on an attempt to determine the wave energy distribution at the ionospheric base by using the simultaneous recording of three field components (B/sub x/, B/sub y/, and E/sub z/) observable on the ground. They present inversion techniques to find how the wave energy density is distributed at the ionospheric base by using the observed fields. The inversion methods proposed are used to estimate the wave distribution functions of magnetospheric VLF waves on the basis of simultaneous measurements of multiple electromagnetic field components }, keywords={ electric field measurement magnetic field measurement magnetospheric electromagnetic wave propagation radio direction-finding radiowave propagation multiple field components measurement ELF waves EM field measurement direction finding radio waves wave energy distribution ionospheric base simultaneous recording inversion techniques observed fields wave distribution functions magnetospheric VLF waves }, mynotes={UNREAD}, }, @ARTICLE{Hayakawa86, author={Hayakawa, M. and Tanaka, Y. and Ohta, K. and Okada, T.}, title={ Absolute intensity of daytime whistlers at low and middle latitudes and its latitudinal variation }, journal={Journal of Geophysics}, volume={59}, number={1}, year={1986}, month={}, pages={67-72}, abstract={ A statistical study of the intensity of daytime whistlers at low (geomag. lat. 25 degrees ) and middle (35 degrees ) latitudes has been made, based on data obtained by the field-analysis of a direction finding system based on the simultaneous measurement of two horizontal magnetic field components and one vertical electric field component. At low latitudes, the maximum absolute intensity is estimated to be 250 mu V/m, while the corresponding maximum intensity at middle latitudes amounts to 600 mu V/m. This latitudinal variation of daytime intensity is interpreted in terms of the joint influence of (a) source activity, (b) magnetospheric propagation effect and (c) ionospheric transmission loss. As the result, it is found that whistlers at each station are attributed to ducted propagation in the magnetosphere and have excited the ionosphere close to each observing station }, keywords={ atmospheric electromagnetic wave propagation ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation whistlers magnetosphere radiowave emission ionosphere intensity daytime whistlers middle latitudes latitudinal variation source activity magnetospheric propagation ionospheric transmission loss ducted propagation }, mynotes={UNREAD}, }, @ARTICLE{HayakawaFeb86, author={Hayakawa, M. and Tanaka, Y. and Sazhin, S.S. and Okada, T. and Kurita, K.}, title={ Characteristics of dawnside mid-latitude VLF emissions associated with substorms as deduced from the two-stationed direction finding measurement }, journal={Planetary and Space Science}, volume={34}, number={2}, year={1986}, month={Feb}, pages={225-43}, abstract={ Mid-latitude VLF emissions are found to take place in close association with geomagnetic substorms at two local times: one at dawn and the other pre-midnight. The characteristics of dawnside VLF emissions are examined, based on the data obtained by the VLF/ELF campaign during November 1978 to February 1979 by means of the direction finding measurements at two stations, Brorfelde in Denmark (L approximately 3) and Chambon-la-Foret in France (L approximately 2). Six events have been analyzed. It is shown that all the features can be understood within the quasi-linear model of cyclotron instability of the electrons injected in association with geomagnetic substorms }, keywords={ atmospheric radiation magnetic storms magnetic storm AD 1978 11 to 1979 02 atmosphere radiation magnetosphere dawnside mid-latitude VLF emissions substorms November 1978 to February 1979 Brorfelde Denmark Chambon-la-Foret France quasi-linear model cyclotron instability }, mynotes={UNREAD}, }, @ARTICLE{HayakawaMay84, author={Hayakawa, M. and Yamanaka, Y. and Parrot, M. and Lefeuvre, F.}, title={ The wave normals of magnetospheric chorus emissions observed on board GEOS 2 }, journal={Journal of Geophysical Research}, volume={89}, number={A5}, year={1984}, month={May}, pages={2811-21}, abstract={ The wave normal directions of magnetospheric chorus emissions have been analyzed by using data from the geostationary GEOS 2 satellite which is located in the equatorial region at L=6.6. As the result of analyses for December 19, 1979, chorus is found to be generated in conjunction with substorms and at local times from around midnight to afternoon. Two types of chorus are observed: impulsive burstlike and rising tone. The wave normals are determined using only the magnetic field data. The wave normals of the rising tones having normal values of df/dt are found to take very small angles (5 degrees -20 degrees ). The rising tones with larger values of df/dt have shown larger wave normal angles of 30 degrees -45 degrees . These relatively small angles support the loss cone instability as the generation mechanism. The impulsive chorus is found to take slightly larger wave normal angles than most rising tones }, keywords={ atmospherics magnetosphere magnetospheric electromagnetic wave propagation plasma plasma instability whistlers whistler mode emissions atmospherics impulsive burstlike chorus AD 1979 12 19 Earth radii 006.6 plasma instability magnetosphere EM wave propagation oblique resonance cone magnetic field aligned wave propagation dawn chorus magnetospheric chorus emissions wave normal directions geostationary GEOS 2 satellite equatorial region December 19, 1979 substorms local times midnight afternoon magnetic field data rising tones wave normal angles loss cone instability generation mechanism }, mynotes={UNREAD}, }, @ARTICLE{HayakawaApr95, title={ Association of whistlers with lightning discharges on the Earth and on Jupiter }, journal={J. Atmos. Terr. Phys. (UK), Journal of Atmospheric and Terrestrial Physics}, volume={57}, number={5}, year={1995}, month={Apr}, pages={525-35}, abstract={ The association between whistlers and lightning discharges has been reviewed on the basis of terrestrial ionospheric satellite observations of VLF radio noise. Evidence indicating that the observed low-latitude radio noise is associated with thunderstorms includes (1) amplitude distribution and noise properties, (2) geographical location, (3) diurnal variation in activity, and (4) diurnal variation of frequency spectrum. Corresponding studies on the propagation of sferics in the Jovian ionosphere and the excitation of whistlers on Jupiter are presented and compared with the terrestrial studies }, keywords={ Jupiter lightning planetary atmospheres whistlers lightning discharges Earth Jupiter terrestrial ionospheric satellite observations VLF radio noise low-latitude radio noise thunderstorms amplitude distribution geographical location diurnal activity variation diurnal frequency spectrum variation sferics propagation whistler excitation }, mynotes={UNREAD}, }, @ARTICLE{HayakawaOct92, title={ Mid-latitude and plasmaspheric hiss: a review }, journal={Planetary and Space Science}, volume={40}, number={10}, year={1992}, month={Oct}, pages={1325-38}, abstract={ A review of mid-latitude and plasmaspheric hiss-type emissions observed at ground-based stations and in the Earth's magnetosphere is presented. Different approaches to modelling of these emissions are discussed. It is pointed out that mid-latitude hiss emissions are most likely to be generated in the equatorial magnetosphere where the energy of electrons is transferred to wave energy via the electron cyclotron instability. Some quantitative characteristics of these emissions are explained in terms of a quasilinear model of this instability. Many properties of plasmaspheric hiss emissions are likely to be related to the same electron cyclotron instability, although the contribution of other mechanisms cannot be excluded }, keywords={ atmospheric electricity atmospherics magnetosphere plasma plasma instability reviews electron energy transfer VLF atmospherics hiss emissions source regions ELF atmospherics ring current electrons energy wave-particle interactions plasmaspheric hiss ground-based stations Earth's magnetosphere mid-latitude hiss emissions equatorial magnetosphere electron cyclotron instability quasilinear model 5 to 8 kHz 0.1 to 1 kHz 5 keV 3.9 to 10.4 kHz 0.4 to 2.0 Mm }, mynotes={UNREAD}, }, @ARTICLE{HayashiDec94, author={Hayashi, K. and Matsui, H. and Kawano, H. and Yamamoto, T. and Kokubun, S.}, title={ Whistler mode waves observed by MGF search coil magnetometer - polarization and wave normal features of upstream waves near the bow-shock }, journal={Geophysical Research Letters}, volume={21}, number={25}, year={1994}, month={Dec}, pages={2907-10}, abstract={ Whistler mode waves in the frequency range between 1 and 50 Hz in the upstream region very close to the bow shock have been observed by the MGF search coil magnetometer on board the Geotail satellite. The three-component waveform polarization and wave-normal characteristics of the foreshock waves are shown as dynamic spectra. Intense whistler mode wave polarization is found to depended on the angle between the wave propagation and the solar wind. The authors introduce a simple scheme to derive the wave characteristics from a large amount of continuously growing data }, keywords={ electromagnetic wave polarisation magnetospheric electromagnetic wave propagation whistlers magnetosphere MGF search coil magnetometer three-component waveform polarization wave-normal characteristics upstream waves bow shock upstream region Geotail satellite foreshock waves dynamic spectra intense whistler mode wave polarization wave propagation solar wind direction 1 to 50 Hz }, mynotes={UNREAD}, }, @ARTICLE{HelliwellApr90, author={Helliwell, R.A. and Mielke, T. and Inan, U.S.}, title={ Rapid whistler-mode wave growth resulting from frequency-time curvature }, journal={Geophysical Research Letters}, volume={17}, number={5}, year={1990}, month={Apr}, pages={599-602}, abstract={ The rapid (<50 ms) temporal growth of ducted whistlers is simulated using controlled injection of VLF pulses from the Siple Station, Antarctica transmitter. The results show that, when the frequency-time function of the injected pulse has a positive slope and negative curvature, producing a kind of 'chirp' such that it approximates the f(t) shape of a lightning-generated whistler at frequencies above the 'nose' frequency, growth up to a saturation level (20-30 dB) commonly occurs within <50 ms as opposed to 200-300 ms that is required for monochromatic input signals. The phenomenon is explained in terms of second-order-resonance theory }, keywords={ whistlers whistlers EM wave rapid growth whistler-mode wave growth frequency-time curvature ducted whistlers controlled injection VLF pulses Siple Station injected pulse second-order-resonance theory }, mynotes={UNREAD}, }, @ARTICLE{HilgersJun92, author={Hilgers, A. and de Feraudy, H. and Le Queau, D.}, title={ Measurement of the direction of the auroral kilometric radiation electric field inside the sources with the Viking satellite }, journal={Journal of Geophysical Research}, volume={97}, number={A6}, year={1992}, month={Jun}, pages={8381-90}, abstract={ The spin modulation of the high-frequency noise from one electric antenna of the Viking satellite has been used to determine for the first time the direction of the polarization plane of the auroral kilometric radiation (AKR) inside the sources of the radiation (i.e., at the local frequency of generation). The observations show a clear difference between the modulation patterns obtained inside the AKR sources and the ones obtained far from them. The measurements made during 36 AKR source crossings have been compared with a theoretical model accounting for the specific Viking antenna equipment. This statistical study shows that, inside the sources, the wave electric field is directed perpendicular to the static magnetic field, within 10 degrees . This observation, consistent with a wave generation by the cyclotron maser instability }, keywords={ atmospheric radiation magnetosphere AKR magnetosphere radiowave emission plasma instability direction auroral kilometric radiation electric field satellite spin modulation high-frequency noise electric antenna Viking polarization wave generation cyclotron maser instability 3 to 30 kHz }, mynotes={UNREAD}, }, @ARTICLE{HirariJan96, author={Hirari, M. and Hayakawa, M.}, title={ A Bayesian regularization approach to ill-posed problems with application to the direction finding of VLF/ELF radio waves }, journal={IEICE Transactions on Communications}, volume={E79-B}, number={1}, year={1996}, month={Jan}, pages={63-9}, abstract={ In this communication we propose to solve the problem of reconstruction from limited data using a statistical regularization method based on a Bayesian information criterion. The minimization of the Bayesian information criterion, which is used here as an objective index to measure the goodness of an estimate, gives the optimum value of the smoothing parameter. By doing so, we could reduce the inversion problem to a simple minimization of a one-variable nonlinear function. The application of such a technique overcomes the non-uniqueness of the solution of the ill-posed problem and all shortcomings of many iterative methods. In the light of simulation and application to real data, we propose a slight modification to the Bayesian information criterion to reconstruct the wave energy distribution at the ionospheric base from the observation of the radio wave electromagnetic field on the ground. The achieved results in both the inversion problem and wave direction-finding are very promising and may support other work, suggesting the use of Bayesian methods in the inversion of ill-posed problems, benefitting from the valuable information brought by a priori knowledge }, keywords={ Bayes methods inverse problems ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation minimisation radio direction-finding radiowave propagation smoothing methods statistical analysis minimization ill-posed problems direction-finding VLF/ELF radio waves signal reconstruction statistical regularization Bayesian information criterion smoothing parameter inversion problem one-variable nonlinear function wave energy distribution ionospheric waves magnetospheric waves }, mynotes={UNREAD}, }, @ARTICLE{HorneJul89, title={ Path-integrated growth of electrostatic waves: the generation of terrestrial myriametric radiation }, journal={Journal of Geophysical Research}, volume={94}, number={A7}, year={1989}, month={Jul}, pages={8895-909}, abstract={ It is generally accepted that electrostatic wave energy is the source of terrestrial myriametric radiation (TMR), but there are several theories to suggest how this energy is converted into TMR. The linear mode conversion 'window' theory of Jones (1976, 1980), which in the past has been considered by some to be too inefficient to account for the observed wave amplitudes, is considered in this article. First, the ray tracing program HOTRAY is described. This program is used to trace electromagnetic and electrostatic waves in a hot magnetized plasma and to calculate the path-integrated growth rates for a realistic unstable particle distribution function. A density model is constructed from wave observations made by DE 1 of an event where TMR was beamed to northern and southern latitudes from a source very close to the magnetic equator. Ray tracking shows that backward propagating electrostatic waves can refract into electromagnetic Z mode waves and transport energy to the so-called radio window at the equator. At this point, mode conversion of energy into O mode radiation is assumed to take place }, keywords={ atmospheric radiation magnetosphere plasma wave magnetosphere TMR electrostatic wave path integrated growth VLF radiowave emission window theory generation terrestrial myriametric radiation linear mode conversion ray tracing program HOTRAY unstable particle distribution function }, mynotes={UNREAD}, }, @ARTICLE{HorneJun88, title={ Ray tracing of electrostatic waves in a hot plasma and its application to the generation of terrestrial myriametric radiation }, journal={Geophysical Research Letters}, volume={15}, number={6}, year={1988}, month={Jun}, pages={553-6}, abstract={ The first results from the program HOTRAY for ray tracing electrostatic and electromagnetic waves in a hot plasma are presented. The calculations are applied to the linear mode-conversion window theory for the generation of terrestrial myriametric radiation corresponding to a specific event observed by the DE-1 satellite. Results show that backward propagating electrostatic waves can refract in a density gradient normal to the magnetic field to become Z-mode waves and can have access to the radio window. Variations of approximately 0.01 degrees in the initial wave normal angle psi can result in a large difference in the transmitted wave intensities. However, if such variations do occur, waves from different locations can still access the radio window so that energy transfer to the conversion point remains efficient. Strong refraction of electrostatic waves at latitude>1 degrees show that the magnetic equator is the preferred location for mode conversion to take place }, keywords={ electromagnetic wave propagation in plasma magnetospheric electromagnetic wave propagation plasma plasma waves radiowave propagation magnetosphere atmosphere radiowave electrostatic waves hot plasma generation terrestrial myriametric radiation HOTRAY ray tracing electromagnetic waves linear mode-conversion window theory DE-1 satellite density gradient magnetic field Z-mode waves radio window initial wave normal angle transmitted wave intensities energy transfer conversion point refraction mode conversion }, mynotes={UNREAD}, }, @ARTICLE{Hu-XiongOct92, author={Hu Xiong and Zhang Xun-Xie}, title={ Interaction between whistler mode wave and the electrons in the magnetosphere }, journal={Chinese Journal of Space Science}, volume={12}, number={4}, year={1992}, month={Oct}, pages={279-86}, abstract={ The nonlinear interaction between the whistler mode wave and the electrons in the magnetosphere reduces the electron's pitch angle and makes some electrons precipitate into the ionosphere, which enhances the local ionization and induces the Trimpi effect. In this paper the equations governing the wave-particle interaction are given and the super particle mode and long-time-scale-method are used to simulate this nonlinear process. When the electrons meet the whistler wave, the phase focus of resonance electrons and phase bunching of unresonance electrons occur. The resonance electrons oscillate asymmetrically in the space zeta ( phi -4)-u/sub /// during the interaction. The inhomogeneity of the geomagnetic field causes a shift of center angle of the trapped region and influences on the whistler wave trapping electrons. This paper also gives the energy flux curves of the electron precipitation with time at an altitude of 1000 km }, keywords={ atmospheric electron precipitation magnetospheric electromagnetic wave propagation whistlers EM wave wave particle interaction nonlinear interaction whistler mode wave electrons magnetosphere pitch angle Trimpi effect wave-particle interaction phase focus phase bunching }, mynotes={UNREAD}, }, @ARTICLE{HughesJul97, author={Hughes, A.R.W. and Rice, W.K.}, title={ A satellite study of low latitude electron and proton whistlers }, journal={Journal of Atmospheric and Solar-Terrestrial Physics}, volume={59}, number={10}, year={1997}, month={Jul}, pages={1217-22}, abstract={ Whistler dispersion, measured on the ISIS 2 satellite, at an altitude of 1400 km, showed a variation with latitude from about 4.5 s/sup 1/2/ at a magnetic latitude ( lambda ) of 30 degrees to about 12+or-2 s/sup 1/2/ at the equator. Frequently, fractional hop whistlers were observed from both hemispheres with dispersions which converged to the same value at the equator. Ray tracing calculations revealed that whistler mode signals of different frequencies take different paths from a source on the ground to the satellite and yet their dispersion is indistinguishable from the Eckersley form. The extent of the entry region to the ionosphere depends on the satellite location and may be more than 300 km for different frequencies. The fractional hop whistlers frequently excite proton whistlers and their crossover frequencies have been used to determine fractional hydrogen ion concentrations. The measurements show that the average fractional H/sup +/ concentrations at 1400 km increase from about 0.80 at lambda =25 degrees to 0.88 at the equator }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation whistlers EM wave magnetosphere ionosphere radiowave propagation low latitude satellite observations proton whistler whistlers electron whistler path dispersion fractional hop whistler ray tracing calculation Eckersley form entry region H/sup +/ concentration }, mynotes={UNREAD}, }, @ARTICLE{HughesFeb77, author={Hughes, W.J. and McPherron, R.L. and Russell, C.T.}, title={ Multiple satellite observations of pulsation resonance structure in the magnetosphere }, journal={Journal of Geophysical Research}, volume={82}, number={4}, year={1977}, month={Feb}, pages={492-8}, abstract={ Data from two intervals when pulsation activity was simultaneously observed on both ATS 1 and OGO 5 satellites are presented. The first example, a Pc 4, indicates that this pulsation is caused by a field line near L=7 resonating in its second-harmonic mode. This is inferred from both plasma density measurements and polarization characteristics. The wave was not observed at three ground stations in the vicinity of the satellite conjugate points. This indicates that Pc 4 waves are very localized in latitude and that a close array (<100 km) is needed to perform effective correlation with satellites. The second event, which is also in the Pc 4 band, can again be inferred to be a field line resonance from the polarization characteristics }, keywords={ magnetohydrodynamic waves magnetosphere micropulsations pulsation resonance structure magnetosphere ATS 1 OGO 5 plasma density polarization characteristics multiple satellite observations Pc 4 pulsation geomagnetic pulsations MHD }, mynotes={UNREAD}, }, @ARTICLE{IkedaApr95, author={Ikeda, M. and Nagano, I. and Shimbo, T. and Carpenter, D.L.}, title={ Intensities and polarization rates of whistler mode VLF signals observed from a ground network near L=4 }, journal={Journal of Geophysical Research}, volume={100}, number={A4}, year={1995}, month={Apr}, pages={5691-703}, abstract={ VLF signals transmitted from Siple station in Antarctica that propagated through the ionosphere and magnetosphere to the northern hemisphere and triggered emissions generated by the Siple signals in the magnetosphere are radiated from wave exit areas on the ionospheric lower boundary. The locations and extent of the wave exit areas are deduced from the wave intensity distributions measured on the ground. In this method the authors use measurements of wave magnetic intensity made simultaneously at six stations. The validity of this method is assessed by comparing the results with values simply estimated from a mathematical evaluation and with results of full wave calculations carried out by Nagano et al. (1986, 1987). The authors find close agreement among results obtained from the three methods and conclude that the wave intensity distribution analysis is valid. As a result of analyzing a triggered emission in detail, the extent of the wave exit area of the downgoing triggered emission is estimated to be 25-50 km or so at an altitude of 80 km. The authors believe that this value relates to the horizontal extent of the duct through which the triggered emission propagated in the magnetosphere and ionosphere and that essentially only direct waves transmitted from the wave source arrive within a range of 200 km from the wave intensity peak on the ground }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation radiowave propagation whistlers whistler mode VLF signals Siple station Antarctica ionosphere magnetosphere triggered emissions wave intensity distributions polarization rates wave exit areas ionospheric lower boundary wave magnetic intensity full wave calculations duct horizontal extent wave intensity peak ground network observations LF 1.5 to 5.5 kHz }, mynotes={UNREAD}, }, @ARTICLE{ImhofDec92, author={Imhof, W.L. and Robinson, R.M. and Collin, H.L. and Wygant, J.R. and Anderson, R.R.}, title={ Simultaneous equatorial measurements of waves and precipitating electrons in the outer radiation belt }, journal={Geophysical Research Letters}, volume={19}, number={24}, year={1992}, month={Dec}, pages={2437-40}, abstract={ Simultaneous wave and precipitating electron measurements near the equator in the outer radiation belt have been made from the CRRES satellite. The electron data of principal concern were acquired in and about the loss cone with narrow angular resolution spectrometers covering the energy range 340 eV to 5 MeV. The wave data included electric field measurements spanning frequencies from 5 Hz to 400 kHz and magnetic field measurements from 5 Hz to 10 kHz. This paper presents examples in which the variations in electron fluxes in the loss cone and the wave intensities were correlated. These variations in electron flux were confined to pitch angles less than about 30 degrees . The association between the flux enhancements and the waves is consistent with wave-induced pitch angle diffusion processes }, keywords={ atmospheric electron precipitation radiation belts electron precipitation magnetosphere trapped particle plasma wave radiowave outer radiation belt flux enhancements wave-induced pitch angle diffusion processes 0.34 to 5000 keV 5 to 400000 Hz }, mynotes={UNREAD}, }, @ARTICLE{InanMar77, author={Inan, U.S. and Bell, T.F. and Carpenter, D.L. and Anderson, R.R.}, title={ Explorer 45 and Imp 6 observations in the magnetosphere of injected waves from the Siple Station VLF transmitter }, journal={Journal of Geophysical Research}, volume={82}, number={7}, year={1977}, month={Mar}, pages={1177-87}, abstract={ Reports the first results of a Stanford University-University of Iowa joint experiment in which VLF waves from the Siple Station transmitter in Antarctica are injected into the magnetosphere along the Earth's magnetic field lines and are detected near the magnetic equatorial plane by the Explorer 45 and Imp 6 spacecraft. The purpose of this experiment is to conduct a controlled in situ study of VLF wave-particle interactions, in particular, to determine the propagation characteristics of the injected waves in the magnetosphere, to determine the regions where VLF emissions are produced, and to determine the effective volume of the magnetosphere illuminated by the Siple transmitter }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation radiowave propagation Explorer 45 Imp 6 magnetosphere injected waves Siple Station VLF transmitter Antarctica wave particle interactions }, mynotes={UNREAD}, }, @ARTICLE{InanApr92, author={Inan, U.S. and Chiu, Y.T. and Davidson, G.T.}, title={ Whistler-mode chorus and morningside aurorae }, journal={Geophysical Research Letters}, volume={19}, number={7}, year={1992}, month={Apr}, pages={653-6}, abstract={ Quasi-electrostatic ELF/VLF chorus emissions immediately above the equatorial half-gyrofrequency, observed to propagate with wave normal angle ( psi ) within 0.4-1.2 degrees of the resonance cone ( psi /sub r/) (Muto et al., 1987), are shown to efficiently resonate with 0.1-10 keV electrons. These waves may thus be important in driving the relatively low energy (<10 keV) component of pulsating aurorae and the morning-side diffuse aurorae ( approximately 1 keV) }, keywords={ atmospheric electron precipitation aurora magnetospheric electromagnetic wave propagation radiowave propagation whistlers whistler mode chorus electron precipitation quasielectrostatic ELF-VLF chorus emission radiowaves magnetosphere morningside aurorae pulsating aurorae diffuse aurorae 0.1 to 10 keV }, mynotes={UNREAD}, }, @ARTICLE{InoueFeb69, title={ Wave trains propagating at an angle to a magnetic field in a collisionless plasma }, journal={Journal of the Physical Society of Japan}, volume={26}, number={2}, year={1969}, month={Feb}, pages={521-8}, abstract={ Non-linear periodic waves propagating at an angle to a magnetic field in a collisionless plasma are studied on the basis of the so-called two-fluid plasma equations. The phenomena to be investigated are assumed to have a length scale of the ion Larmor radius, so that the electron mass may be neglected. The analysis is developed at first for a cold plasma, and then for the plasma with the adiabatic exponent gamma /sub i/= gamma /sub e/=2. In the former case, the solution is expressed in terms of the elliptic integrals in Weierstrass' normal form. The solitary wave solutions are found for the limiting case that the periodicity is infinite }, keywords={ plasma oscillations }, mynotes={UNREAD}, }, @ARTICLE{Irzhichek86, author={Irzhichek, F. and Mal'tseva, O.A. and Titova, E.E. and Triska, P. and Yakhnina, T.A.}, title={ Peculiarities of the propagation of VLF choruses in the magnetosphere }, journal={Geomagnetizm i Aeronomiya}, volume={26}, number={6}, year={1986}, month={}, pages={}, abstract={ An analysis is made using the data of the Interkosmos-19 artificial Earth satellite, of the spatial characteristics of the zone of irradiation of VLF choruses in the upper ionosphere. It is shown that this zone is located in the region of L shells smaller than the L shell of the plasmapause; as magnetic activity increases its spatial size decreases; the northern boundary of the zone is shifted in accordance with the change in position of the plasmapause, and the lower boundary remains practically unchanged (L=2.0-2.5). The differences in the times of arrival of chorus elements at different latitudes in the upper ionosphere are determined. It is shown that one can explain the observed spatial and temporal characteristics of VLF choruses by the effect of a concentration gradient in the region of the plasmapause on the trajectory of VLF waves and on their escape toward the ionosphere }, keywords={ atmospheric radiation magnetospheric electromagnetic wave propagation VLD chorus radiowave propagation propagation magnetosphere upper ionosphere plasmapause trajectory }, mynotes={UNREAD}, }, @ARTICLE{IsenbergMar82, author={Isenberg, P.A. and Koons, H.C. and Fennell, J.F.}, title={ Simultaneous observations of energetic electrons and dawnside chorus in geosynchronous orbit }, journal={Journal of Geophysical Research}, volume={87}, number={A3}, year={1982}, month={Mar}, pages={1495-503}, abstract={ Presents the first simultaneous observations of chorus activity and energetic particles from near-geosynchronous orbit by using data from the Aerospace Corporation VLF receiver and the UCSD charged particle detector on the SCATHA satellite. It was found that, for the 5 days studied, June 23-27, 1979, every encounter with injected clouds of energetic electrons was accompanied by chorus activity. It is concluded that dawnside chorus is generated by substorm-injected, anisotropic clouds of electrons with energies between 10 and 100 keV }, keywords={ atmospheric radiation magnetosphere radio noise EM wave emission magnetosphere energetic electrons dawnside chorus VLF generated substorm-injected }, mynotes={UNREAD}, }, @ARTICLE{IshikawaJan90, author={Ishikawa, K. and Hattori, K. and Hayakawa, M.}, title={ A study of ray focussing of whistler-mode waves in the outer magnetosphere }, journal={Transactions of the Institute of Electronics, Information and CommunicationEngineers E}, volume={E73}, number={1}, year={1990}, month={Jan}, pages={149-54}, abstract={ The purpose of the paper is to investigate the ray focussing of whistler-mode waves in the outer magnetosphere which results in an enhanced wave-particle interaction. The critical frequency at which the whistler-mode refractive index surface exhibits a zero curvature at a longitudinal wave normal, is estimated for the general plasma conditions. This critical frequency determined by the ratio of electron plasma- to gyro-frequency in a homogeneous plasma, is also found from the full-wave theory in a slightly inhomogeneous case. Then, the two-dimensional ray-tracing analyses for an inhomogeneous outer magnetospheric model, have indicated that the strongest ray focussing in the vicinity of the geomagnetic equator is expected slightly below the critical frequency. This kind of study of ray focussing is important in the study of enhanced gyroresonant wave-particle interactions in the outer magnetosphere }, keywords={ magnetospheric electromagnetic wave propagation whistlers whistler mode wave ray focussing critical frequency whistler-mode refractive index surface zero curvature general plasma conditions full-wave theory two-dimensional ray-tracing analyses inhomogeneous outer magnetospheric model geomagnetic equator enhanced gyroresonant wave-particle interactions }, mynotes={UNREAD}, }, @ARTICLE{IwaiSep74, author={Iwai, A. and Okada, T. and Hayakawa, M.}, title={ Rocket measurement of wave normal directions of low-latitude sunset whistlers }, journal={Journal of Geophysical Research}, volume={79}, number={25}, year={1974}, month={Sep}, pages={3870-3}, abstract={ The measurement of the wave normal direction of short whistlers is made in the ionosphere by means of a three-dimensional crossed loop antenna on a rocket. The results of the whistler wave normal direction are presented, and some relationships to the propagation characteristics in the magnetosphere and also to the penetration through the ionosphere are discussed }, keywords={ ionosphere whistlers low latitude sunset whistlers wave normal directions ionosphere magnetosphere }, mynotes={UNREAD}, }, @ARTICLE{JamesJul80, title={ Direction-of-arrival measurements of auroral kilometric radiation and associated ELF data from Isis 1 }, journal={Journal of Geophysical Research}, volume={85}, number={A7}, year={1980}, month={Jul}, pages={3367-75}, abstract={ The spin-modulated noise from the dipole connected to the sounder receiver on the Isis 1 spacecraft has been used along with the computation of ray paths to deduce the direction of propagation of auroral kilometric radiation (AKR). On the basis of three passes with fixed-frequency measurements at 0.48 MHz it is concluded that in the generation region at about 3500-km altitude the wave vectors make an angle between about 60 degrees and 90 degrees with respect to the local magnetic field. That is, they are predominantly downcoming. Also, in using the sounder records the plasma frequency f/sub N/ is found to be very much less than the gyrofrequency f/sub H/ in the generation region. When these Isis observations are combined with previous evidence on AKR, from which it was concluded that it propagates predominantly in the right-hand polarized X mode, serious disagreement with a number of theories, particularly those that predict the left-hand-polarized O mode, results }, keywords={ atmospheric radiation magnetosphere magnetospheric electromagnetic wave propagation kilometric radiation ELF ray path auroral zone magnetosphere LF direction of arrival MF radiowave EM wave propagation }, mynotes={UNREAD}, }, @ARTICLE{Jiricek86, author={Jiricek, F. and Triska, P. and Malteseva, O.A. and Titova, E.E. and Yakhnina, T.A.}, title={ Connection between the upper ionospheric region of VLF chorus occurrence and the plasmapause position }, journal={Studia Geophysica et Geodaetica}, volume={30}, number={4}, year={1986}, month={}, pages={404-10}, abstract={ The occurrence zone of the VLF chorus in the upper ionosphere appears at L-shells lower than the plasmapause position L/sub pp/; with increasing geomagnetic activity the spatial dimension of the zone diminishes, its upper boundary being shifted in correspondence with the plasmapause position, the lower remaining practically without change (L=2.0-2.5). Calculations of propagation paths show that the similarity of the VLF chorus spectrum at different upper-ionospheric latitudes as well as the large spatial dimension of the zone of observation can be explained as special features in the propagation of VLF waves from an equatorial source, starting in the vicinity of the plasmapause with different initial normal angles }, keywords={ atmospheric radiation atmospheric structure atmospherics ionosphere magnetic storms magnetosphere magnetospheric electromagnetic wave propagation chorus zone spatial dimension ionospheric L-shells chorus zone upper boundary shift VLF waves propagation lower boundary equatorial VLF source topside ionosphere plasmapause VLF emission magnetosphere EM wave propagation Interkosmos-19 satellite upper ionospheric region VLF chorus occurrence plasmapause position increasing geomagnetic activity propagation paths VLF chorus spectrum upper-ionospheric latitudes initial normal angles 500 to 1000 km 1.5 to 4 kHz 3.4 to 5.0 Earthradii }, mynotes={UNREAD}, }, @ARTICLE{JohnstoneApr93, author={Johnstone, A.D. and Walton, D.M. and Liu, R. and Hardy, D.A.}, title={ Pitch angle diffusion of low-energy electrons by whistler mode waves }, journal={Journal of Geophysical Research}, volume={98}, number={A4}, year={1993}, month={Apr}, pages={5959-67}, abstract={ It has often been argued that electrons with energy below approximately 10 keV cannot be pitch-angle diffused by whistler mode waves because they have less than a critical minimum parallel energy. The authors show that there is no theoretical justification for an energy threshold based on the grounds of either resonance or instability and present energy/pitch angle plots from the low energy plasma analyzer (LEPA) on the CRRES spacecraft which support this analysis because they have features to be expected from a whistler mode interaction. This shows that whistler mode diffusion is responsible for a substantial amount of low-energy electron precipitation at high latitudes and is probably responsible for the diffuse aurora. Furthermore, the authors show that releasing lithium from the CRRES spacecraft in the outer zone was unlikely to stimulate precipitation or to trigger substorm }, keywords={ atmospheric electron precipitation magnetospheric electromagnetic wave propagation whistlers low-energy electrons whistler mode waves energy/pitch angle plots low energy plasma analyzer LEPA CRRES interaction whistler mode diffusion electron precipitation diffuse aurora 10 keV Li release }, mynotes={UNREAD}, }, @ARTICLE{JonesOct83, author={Jones, D. and Lefeuvre, F. and Parrot, M.}, title={ Characteristics of VLF emissions manifested by their cross-spectral phase information }, journal={Planetary and Space Science}, volume={31}, number={10}, year={1983}, month={Oct}, pages={1083-97}, abstract={ Natural VLF emissions received by a single antenna can be characterised at each point in the emissions' frequency-time domain by a power and a phase. Emissions received at a single point by two antennae with a fixed relative orientation in space can be similarly described by the cross-spectral power and relative phase. It is shown that the cross-spectral phase contains information on the propagation characteristics of the waves which is better utilised in wave analysis than the power. In fact, the phase information allows weak signals to be identified more readily than is possible from a power spectrogram. It also allows the recognition of waves propagating with different wave normal directions. Data from the Geos-1 electric and magnetic antennae, pre-processed by the on-board correlator, are used to study the cross-spectral characteristics of VLF hiss and chorus in the Earth's magnetosphere }, keywords={ atmospheric techniques ionosphere ionospheric electromagnetic wave propagation magnetosphere magnetospheric electromagnetic wave propagation whistlers radiowave emission AD 1977 ionosphere cross phase spectrogram technique whistlers telemetry VLF emissions cross-spectral phase information frequency-time domain propagation weak signals cross-spectral characteristics VLF hiss chorus magnetosphere }, mynotes={UNREAD}, }, @ARTICLE{JonesMay83, author={Jones, D. and Lefeuvre, F. and Parrot, M.}, title={ VLF signal recognition by cross-spectral analysis }, journal={Annales Geophysicae}, volume={1}, number={3}, year={1983}, month={May}, pages={253-8}, abstract={ A method is described whereby magnetospheric VLF signals can be preprocessed and so reduce the amount of data that has to be telemetered (from satellites or remote Antarctic stations). The method entails the use of the cross-spectral phase, and in particular its stationarity with time, to extract the signal. The technique has been tested on natural VLF emissions recorded on GEOS 1 and the results illustrate that, not only do they support the predictions made on the basis of the earlier simulations, but they also allow the emissions to be viewed from a new perspective. They permit information to be obtained on the propagation characteristics of the waves which was not possible from the cross-spectral power or from the coherence function. The potential of the method for distinguishing signal from noise and for displaying wave propagation characteristics is illustrated using VLF hiss and chorus observed on GEOS 1 }, keywords={ atmospheric radiation atmospheric techniques magnetosphere magnetosphere radiowave emission VLF radiosignal plasma waves signal recognition cross-spectral analysis cross-spectral phase wave propagation }, mynotes={UNREAD}, }, @ARTICLE{Karpman76, author={Karpman, V.I. and Shklyar, D.R.}, title={ Particle precipitation in the magnetosphere under the effect of monochromatic VLF-signals }, journal={Geomagnetizm i Aeronomiya}, volume={16}, number={3}, year={1976}, month={}, pages={}, abstract={ The nature of resonance interaction of a whistler wave with electrons in an inhomogeneous plasma (magnetosphere) is considered. The propagation of wave along a line with L=4 is investigated. The resonance condition for particles (i) with a pitch angle near the boundary of the loss cone (these particles are essential for precipitation) and (ii) particles interacting with the wave in the equatorial region is given. As a result of their resonance interaction with the waves, these particles can enter the loss cone and precipitate in the zone of emission of the VLF signal. Particles that are not trapped in phase participate mainly in resonance interaction leading to precipitation }, keywords={ atmospheric electron precipitation magnetosphere magnetospheric electromagnetic wave propagation magnetosphere resonance interaction whistler wave inhomogeneous plasma pitch angle loss cone monochromatic VLF signals particle precipitation }, mynotes={UNREAD}, }, @ARTICLE{KarpmanOct92, author={Karpman, V.I. and Kaufman, R.N. and Shagalov, A.G.}, title={ Self-focusing of whistler waves }, journal={Physics of Fluids B (Plasma Physics)}, volume={4}, number={10}, year={1992}, month={Oct}, pages={3087-100}, abstract={ The theory of axially symmetric self-focusing of whistler waves, based on the full system of Maxwell equations, is developed. The plasma is described by the magnetohydrodynamic equations including the ponderomotive force from RF field. The nonlinear Schrodinger equations (NSE) for arbitrary azimuthal modes of whistler waves are derived. It is shown that they differ from the NSE for a scalar field; this is connected with an intrinsic angular momentum due to the rotating polarization of whistlers. It is shown that the self-focusing, as described by the NSE, differs in its final stage from the results following from the full set of Maxwell equations. The latter gives defocusing after sufficient narrowing of the initial wave beam, due to transformation of the trapped wave into a nontrapped branch which is not contained in the NSE description. The oscillatory character of the defocusing is demonstrated }, keywords={ Maxwell equations plasma magnetohydrodynamics plasma waves Schrodinger equation self-focusing whistlers whistler waves axially symmetric self-focusing Maxwell equations plasma magnetohydrodynamic equations ponderomotive force RF field nonlinear Schrodinger equations }, mynotes={UNREAD}, }, @ARTICLE{KasaharaJul94, author={Kasahara, Y. and Kenmochi, H. and Kimura, I.}, title={ Propagation characteristics of the ELF emissions observed by the satellite Akebono in the magnetic equatorial region }, journal={Radio Science}, volume={29}, number={4}, year={1994}, month={Jul}, pages={751-67}, abstract={ Emissions with their frequencies below 100 Hz are often observed by the Akebono satellite in the vicinity of the geomagnetic equatorial plane. These ELF emissions are classified into two types. One is an ion cyclotron wave below the local proton cyclotron frequency and the other is assumed to be magnetosonic wave observed not only below but also above the local proton cyclotron frequency. The wave normal directions of the latter type of emissions were estimated by using the wave distribution function method. It is found that the emissions are propagating with their wave normal direction nearly perpendicular to the meridian plane. The propagation characteristics of these emissions are also examined by ray tracing including the effects of ions. The ray tracing study clarified that the wave can propagate around the plasmapause because of the trapping effect of density gradient. In this paper we propose that these emissions are generated just outside the plasmapause and are propagating around the plasmapause with their wave normal nearly perpendicular to the geomagnetic field line and to the meridian plane }, keywords={ artificial satellites electromagnetic wave propagation in plasma geomagnetism radiowave propagation ray tracing ELF emissions Akebono satellite propagation characteristics geomagnetic equatorial plane ion cyclotron wave local proton cyclotron frequency magnetosonic wave wave normal directions wave distribution function method meridian plane ray tracing plasmapause trapping effect density gradient geomagnetic field 100 Hz }, mynotes={UNREAD}, }, @ARTICLE{KaufmanMay85, title={ Azimuth-dependent whistler modes during propagation in axisymmetric ducts }, journal={Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika}, volume={28}, number={5}, year={1985}, month={May}, pages={566-73}, abstract={ Exact solution of Maxwell's equations for a homogeneous magnetoactive plasma depending on all three cylindrical coordinates, and also WKB solutions for a weakly inhomogeneous magnetoactive plasma are obtained in the whistler frequency range. These solutions are used for the analysis of waveguide propagation of whistlers in axisymmetric ducts with enhanced density. Estimates of the number of modes and an expression for the cutoff frequency, which depends on the harmonic number associated with the azimuth angle, are obtained for weak ducts with a typical electron density profile }, keywords={ electromagnetic wave propagation in plasma magnetospheric electromagnetic wave propagation plasma radiowave propagation whistlers Maxwell equations azimuth-dependent whistler modes radiowave magnetosphere propagation axisymmetric ducts homogeneous magnetoactive plasma cylindrical coordinates weakly inhomogeneous magnetoactive plasma whistler frequency range waveguide propagation enhanced density modes cutoff frequency azimuth angle electron density profile }, mynotes={UNREAD}, }, @ARTICLE{Kimura90, author={Kimura, I. and Hashimoto, K. and Nagano, I. and Okada, T. and Yamamoto, M. and Yoshino, T. and Matsumoto, H. and Ejiri, M. and Hayashi, K.}, title={ VLF observations by the Akebono (EXOS-D) satellite }, journal={Journal of Geomagnetism and Geoelectricity}, volume={42}, number={4}, year={1990}, month={}, pages={459-78}, abstract={ The VLF wave instruments on board Akebono involve a wide band analyzer (WBA), multi-channel analyzers (MCA), Poynting flux analyzers (PFX), ELF frequency analyzers and a vector impedance probe (VIP) and cover a frequency range from a few Hz to 17.8 kHz for electric and magnetic field components. The main objectives of the wave observations are to investigate the wave phenomena closely associated with energetic particle precipitation in the auroral zone and the physics of wave-wave and wave-particle interaction phenomena. In order to clarify these wave characteristics, the determination of the wave normal direction and the direction of the Poynting vectors are essential. The VLF instruments, especially PFX and ELF, are designed to satisfy such requirements. The authors introduce all the subsystems of the VLF instruments and some preliminary results of observations to show the characteristic features of each subsystem }, keywords={ artificial satellites atmospheric measuring apparatus magnetospheric electromagnetic wave propagation radiowave propagation EXOS-D VLF wave instruments Akebono wide band analyzer multi-channel analyzers Poynting flux analyzers ELF frequency analyzers vector impedance probe wave observations energetic particle precipitation auroral zone wave-particle interaction 3.16 Hz to 17.8 kHz }, mynotes={UNREAD}, }, @ARTICLE{KimuraSep96, author={Kimura, I. and Hikuma, A. and Kasahara, Y. and Oya, H.}, title={ Electron density distribution in the plasmasphere in conjunction with IRI model, deduced from Akebono wave data }, journal={Adv. Space Res. (UK), Advances in Space Research}, volume={18}, number={6}, year={1996}, month={Sep}, pages={279-88}, abstract={ Determination of electron density distribution in the plasmasphere has been attempted using wave normal directions and delay time of Omega signals, and in situ electron density observed on the Akebono satellite. The present study is based on the assumption that the plasma model is represented by a diffusive equilibrium model with a vertical temperature gradient, and the electron density at a reference altitude (1000 km) being dependent on the L value. The parameters related to these models were determined by non-linear least square fitting of the in situ electron density, the wave normal direction and delay time of Omega signals observed by Akebono. Relative concentrations of ion constituents of H/sup +/, He/sup +/, O/sup +/ at the reference altitude are determined by fitting as either L independent or L dependent. Connecting the global plasmaspheric density model with IRI in the ionospheric altitude is also tried }, keywords={ electron density helium hydrogen ionosphere magnetosphere oxygen positive ions electron density distribution plasmasphere IRI model Akebono wave data plasma model diffusive equilibrium model vertical temperature gradient nonlinear least square fitting ion density global plasmaspheric density model H/sup +/ He/sup +/ O/sup +/ 1000 km H He O }, mynotes={UNREAD}, }, @ARTICLE{KimuraFeb95, author={Kimura, I. and Hikuma, A. and Kasahara, Y. and Sawada, A. and Kikuchi, M. and Oya, H.}, title={ Determination of electron density distributions in the plasmasphere by using wave data observed by Akebono satellite }, journal={Adv. Space Res. (UK), Advances in Space Research}, volume={15}, number={2}, year={1995}, month={Feb}, pages={103-7}, abstract={ Determination of electron density distribution in the plasmasphere has been attempted using wave normal directions and delay time of Omega signals observed on the Akebono satellite as well as the electron density along the satellite trajectory }, keywords={ atmospheric techniques magnetosphere magnetosphere plasma density electron density distribution plasmasphere Akebono satellite radiowave method measurement technique wave normal direction delay time Omega signal radiosignal propagation }, mynotes={UNREAD}, }, @ARTICLE{KimuraJan83, author={Kimura, I. and Matsumoto, H. and Mukai, T. and Hashimoto, K. and Bell, T.F. and Inan, U.S. and Helliwell, R.A. and Katsufrakis, J.P.}, title={ EXOS-B/Siple Station VLF wave-particle interaction experiments. I. General description and wave-particle correlations }, journal={Journal of Geophysical Research}, volume={88}, number={A1}, year={1983}, month={Jan}, pages={282-94}, abstract={ In situ measurements of both energetic particles and VLF waves have been carried out in a joint program involving the Japanese satellite EXOS-B and the Siple Station VLF transmitter. A general description of the experiment is given as well as some results concerning wave particle correlations. Correlations of electron flux and pitch angle anisotropy in the energy range from 85 eV to 6.9 keV with waves in a range from 300 Hz to 9 kHz are examined. These electrons sometimes have a pitch angle distribution with a peak flux at 90 degrees pitch angle (so-called pancake distribution). On five passes out of a total of 50 during the summer campaign in 1979, the energy of the electrons that showed a high pitch angle anisotropy shifted upward as the satellite moved into the plasmasphere, crossing the plasmapause in the equatorial region. In two cases out of five, strong Siple signals were observed in the geomagnetic equatorial region just outside the plasmapause, in association with such a pancake pitch angle distribution of electrons. The Siple signals are most likely amplified by the cyclotron instability due to the high pitch angle anisotropy (HPAA) }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation AD 1979 propagation radiowave heating experiment magnetosphere trapped particle wave-particle interaction wave-particle correlations VLF electron flux pitch angle anisotropy plasmasphere }, mynotes={UNREAD}, }, @CONFERENCE{Kimura85, author={Kimura, I. and Matsuo, T. and Tsuda, M. and Yamauchi, K.}, title={ 3-D ray tracing of whistler mode waves in a non-dipolar magnetosphere }, booktitle={ISAP Japan 1985. Proceedings of the 1985 International Symposium onAntennas and Propagation, Japan - A Step to New Radio Frontiers}, volume={}, number={}, year={1985}, month={}, pages={987-90 vol.3}, abstract={ Ray tracing with a computer, of the whistler mode waves in the magnetosphere surrounding the Earth has often been made to interpret various whistler mode phenomena observed on the ground and on satellites. In these calculations, analytical models of the geomagnetic field and ion densities in the medium are required. Thus far, a dipole model has been assumed for the geomagnetic field and a diffusive equilibrium model for plasma density. Most of the ray tracing has been confined to the meridian plane. The ray tracing program is modified to accommodate a more realistic geomagnetic field model, including higher spherical harmonic moments in addition to the dipole. A more realistic electron density model is used as well }, keywords={ magnetospheric electromagnetic wave propagation radiowave propagation whistlers nondipolar magnetosphere radiowave propagation 3-D ray tracing whistler mode waves magnetosphere geomagnetic field ion densities dipole model diffusive equilibrium model plasma density meridian plane realistic electron density model }, mynotes={UNREAD}, }, @ARTICLE{KimuraFeb91, author={Kimura, I. and Wong, A. and Chouinard, B. and Okada, T. and Mccarrick, M. and Nagano, I. and Hashimoto, K. and Wuerker, R. and Yamamoto, M. and Ishida, K.}, title={ Satellite and ground observations of HIPAS VLF modulation }, journal={Geophysical Research Letters}, volume={18}, number={2}, year={1991}, month={Feb}, pages={309-12}, abstract={ Joint experiments between the new Japanese satellite EXOS-D and the HIPAS (High Power Active Stimulation) facility located at Fairbanks, Alaska were made in 1989. The HF radiation was modulated in amplitude by a 2.5 kHz signal. On November 28, 1989, EXOS-D detected the VLF signal at an altitude of 2300 km with an E field of 15 mu V/m and a B field of 0.25 pT. The angle between the wave normal and the geomagnetic field was less than 20 degrees . Simultaneous ground observations were made using loop antennas at a distance about 35 km from HIPAS. The 2.5 kHz signal amplitude there at the time of the satellite observation was 1.3 pT. If this wave magnetic field is assumed to be due in an ionospheric AC current of 0.65 A, the signal strength at the satellite is roughly consistent within a factor of 3 }, keywords={ ionosphere ionospheric electromagnetic wave propagation ionosphere radiowave propagation modification experiment AD 1989 radiowave heating HIPAS VLF modulation HF radiation modulated }, mynotes={UNREAD}, }, @ARTICLE{King-Wang-ChanFeb72, author={King-Wang Chan, Burton and R.K. and Holzer, R.E.}, title={ Measurement of the wave-normal vector of proton-whistlers on Ogo 6 }, journal={Journal of Geophysical Research}, volume={77}, number={4}, year={1972}, month={Feb}, pages={635-9}, abstract={ The first experimental determination of the wave-normal vector of proton whistlers in the ionosphere is described. Between the crossover frequency and the proton gyrofrequency, both right-hand and left- hand modes of propagation can occur for upgoing waves. Theoretically, the amount of energy in the respective modes depends on theta , the angle between the wave normal and the magnetic field. For proton whistlers with only left-hand mode energy between the crossover and proton gyrofrequency, theta ranged from 36 degrees to 51 degrees . For proton whistlers with strong right-hand and left-hand mode signals, theta ranged from 24 degrees to 29 degrees . The result is in good agreement with Wang's (1971) collisionless mode-coupling model. The angle between the wave normal and the vertical is found to increase with increasing altitude }, keywords={ ionospheric electromagnetic wave propagation ionospheric measurement proton whistlers ionosphere crossover frequency proton gyrofrequency mode signals Ogo 6 satellite observations wave normal vectors }, mynotes={UNREAD}, }, @ARTICLE{KitagawaDec96, author={Kitagawa, T. and Ohta, K. and Shima, N. and Hayakawa, M. and Dowden, R.L.}, title={ Ducted and nonducted whistlers at mid latitude }, journal={Memoirs of College of Engineering, Chubu University}, volume={32}, number={}, year={1996}, month={Dec}, pages={49-55}, abstract={ The ground-based direction finding of mid-latitude whistlers carried out at Otago, New Zealand (L=2.78) has yielded the exit points of whistlers in the lower ionosphere by the field analysis method. The field analysis direction finding measurement has been applied to multi-path whistlers, and one multi-path whistler was found to have penetrated through the ionosphere very close to the station of Otago. Though these multi-path whistlers are so-called diffused whistlers, there is one pure tone whistler. The electron density of the path of this pure tone whistler measured by the nose extension method is much smaller than that of other diffused whistlers. The authors discuss the propagation mechanism of this pure tone whistler by using ray tracing }, keywords={ ionospheric electromagnetic wave propagation whistlers ducted whistlers nonducted whistlers ground-based direction finding midlatitude whistlers Otago New Zealand whistler exit points field analysis method lower ionosphere field analysis direction finding measurement multipath whistlers diffused whistlers pure tone whistler electron density nose extension method propagation mechanism ray tracing }, mynotes={UNREAD}, }, @ARTICLE{KondratevMar92, author={Kondrat'ev, I.G. and Kudrin, A.V. and Zaboronkova, T.M.}, title={ Radiation of whistler waves in magnetoactive plasma }, journal={Radio Science}, volume={27}, number={2}, year={1992}, month={Mar}, pages={315-24}, abstract={ The radiation of ring electric and magnetic currents in a magnetoactive plasma in the whistler frequency range is investigated. Particular attention is concentrated on the problem of variation of the radiated power distribution over the spectrum of the excited waves with the variation of the radiator parameters. Attention is also given to the radiation pattern structure near the resonance cone and the peculiar caustic directions corresponding to the conic refraction and the Storey angle. It is shown that for the ring electric current the consideration of the inhomogeneity in its distribution along the ring can be of importance and can lead, in particular, to a large increase of the relative contribution of the quasi-electrostatic whistler mode waves to the total radiation power. Detailed numerical calculations have been carried out for conditions close to ionospheric conditions }, keywords={ astrophysical plasma astrophysical radiation mechanisms atmospheric electricity atmospheric radiation geomagnetism ionosphere ionospheric electromagnetic wave propagation plasma plasma transport processes plasma waves whistlers ionospheric whistlers ring magnetic current inhomogeneous ring electric current homogeneous ring electric current waves spectral energy distribution whistler waves magnetoactive plasma whistler frequency range radiated power distribution radiator parameters radiation pattern structure resonance cone caustic directions conic refraction Storey angle quasi-electrostatic whistler mode waves total radiation power }, mynotes={UNREAD}, }, @ARTICLE{KoonsOct90, author={Koons, H.C. and Roeder, J.L.}, title={ A survey of equatorial magnetospheric wave activity between 5 and 8 R/sub E/ }, journal={Planetary and Space Science}, volume={38}, number={10}, year={1990}, month={Oct}, pages={1335-41}, abstract={ The authors report the results of a survey of ELF/VLF wave activity in the frequency range from 100 Hz to 5 kHz observed by the SCATHA satellite near the magnetic equator between 5 and 8 R/sub E/. The typical wave environment in this region is required to assess the role of each type of wave in transport processes, such as the pitch-angle diffusion of electrons, occurring in the outer magnetosphere. Hiss, discrete whistler-mode emissions and electron cyclotron harmonic waves occur within the frequency range of the SCATHA VLF receiver. Hiss is predominantly observed between noon and dusk where the satellite frequently enters the plasmasphere. Discrete whistler-mode emissions occur over 60% of the time between 03:00 and 12:00 LT }, keywords={ magnetosphere whistlers ELF VLF hiss atmospheres equatorial magnetospheric wave activity SCATHA satellite transport processes pitch-angle diffusion electrons discrete whistler-mode emissions electron cyclotron harmonic waves plasmasphere 5 to 8 Earthradii 100 Hz to 5 kHz }, mynotes={UNREAD}, }, @ARTICLE{KoonsAug83, author={Koons, H.C. and Fennell, J.F.}, title={ Particle and wave dynamics during plasma injections }, journal={Journal of Geophysical Research}, volume={88}, number={A8}, year={1983}, month={Aug}, pages={6221-9}, abstract={ The SCATHA satellite measures particle and wave parameters as it moves outbound on the duskside from the plasmasphere into the plasma sheet. In many cases plasma waves are not observed in the quiescent plasma sheet prior to a plasma injection. The electron distribution function prior to entry into the plasma sheet is a nearly isotropic soft spectrum, J(E) approximately 1/E. Just inside the plasma sheet the spectrum begins to harden and becomes anisotropic, J/sub perpendicular to />J/sub ///. As the satellite penetrates deeper into the plasma sheet, the spectrum further hardens, especially near alpha /sub 0/ approximately 90 degrees . At the injection the electron spectrum drastically hardens and often becomes peaked in the keV energy range. The pitch angle anisotropy is further enhanced in favor of J/sub perpendicular to /. The plasma wave emissions onset occurred as the time of the injection. Whistler mode waves are observed below the electron cyclotron frequency. Electrostatic waves are detected in bands between the electron cyclotron frequency harmonics }, keywords={ magnetosphere trapped particle magnetosphere AD 1979 substorm wave dynamics plasma injections plasmasphere plasma sheet plasma waves pitch angle anisotropy }, mynotes={UNREAD}, }, @ARTICLE{KoonsSep85, title={ Whistlers and whistler-stimulated emissions in the outer magnetosphere }, journal={Journal of Geophysical Research}, volume={90}, number={A9}, year={1985}, month={Sep}, pages={8547-51}, abstract={ Lightning-generated VLF whistlers are rarely detected by the VLF receiver aboard the SCATHA satellite. This satellite has an inclination of 7.9$OD and covers a range of L shells from 5.5 to 9.0 near the magnetic equator. The general absence of whistlers suggests that there are few if any propagation paths from the Earth-ionosphere waveguide to the outer regions of the magnetosphere, especially to regions outside the plasmasphere. Since radiation at VLF from lightning is much stronger than power line harmonic radiation, it is unlikely that power line harmonic radiation is present outside the plasmasphere. It is considered that whistlers and power line harmonic radiation do not play a significant role in wave-particle interactions in the outer magnetosphere }, keywords={ magnetospheric electromagnetic wave propagation whistlers whistler-stimulated emissions outer magnetosphere VLF whistlers SCATHA satellite propagation paths Earth-ionosphere waveguide lightning power line harmonic radiation plasmasphere wave-particle interactions }, mynotes={UNREAD}, }, @ARTICLE{KoonsJun74, title={ Plasmapause crossings determined by using the oblique plasma resonance excited by a satellite-borne RF antenna }, journal={Journal of Geophysical Research}, volume={79}, number={16}, year={1974}, month={Jun}, pages={2526-8}, abstract={ The location of the plasmapause has been measured by an oblique plasma resonance technique. The angle with respect to the geomagnetic field at which this resonance occurs is sensitive to the ambient electron density. During magnetically quiet conditions, abrupt changes in this angle, implying a steep electron density gradient, occur between L=3.2 and L=3.6 between 0400 and 0500 LT. This location agrees with the expected location of the plasmapause at that time as measured by the whistler dispersion technique }, keywords={ electromagnetic wave propagation in plasma electron density magnetosphere radiowave propagation plasmapause crossings oblique plasma resonance geomagnetic field ambient electron density magnetically quiet conditions whistler dispersion technique magnetoplasma polar orbiting satellite OV1-20S satellite borne RF antenna 600 to 1200 kHz MF }, mynotes={UNREAD}, }, @ARTICLE{Krauss-VarbanApr94, author={Krauss-Varban, D. and Omidi, N. and Quest, K.B.}, title={ Mode properties of low-frequency waves: kinetic theory versus Hall-MHD }, journal={Journal of Geophysical Research}, volume={99}, number={A4}, year={1994}, month={Apr}, pages={5987-6009}, abstract={ In fluid theory, the ordering of low-frequency modes in a homogeneous plasma is based on the phase velocity, since modes do not intersect each other in dispersion diagrams as a function of wavenumber or other parameters. In linear kinetic theory, modes cross each other. Thus a consistent and useful classification should be based on the physical properties of the modes instead. This paper attempts such a classification by documenting the dispersion and general mode properties of the low-frequency waves ( omega <<( Omega /sub ci/ Omega /sub ce/)/sup 1/2/, where Omega /sub ci/, Omega /sub ce/ are the cyclotron frequencies of the ions and electrons, respectively) in kinetic theory, and by comparing them to the results of two-fluid theory. Kinetic theory gives a separate Alfven/ion-cyclotron wave with phase speed omega /k approximately=v/sub A/ cos theta for omega << Omega /sub ci/, where v/sub A/ is the Alfven velocity and theta the angle of propagation between wave vector k and background magnetic field B/sub o/. For a given wavenumber, the magnetosonic mode is a double-valued solution with a singular point in theta , beta parameter space, where beta is the ratio of thermal pressure to magnetic pressure. It is shown that a branch cut starting at the singular point theta approximately 30 degrees , beta approximately 3 and leading to larger beta gives a practical and consistent separation of this double-valued magnetosonic solution. Selection of this branch cut results in a moderately damped fast/magnetosonic and a heavily damped slow/sound wave. A comprehensive review of the polarization, compressibility and other mode properties is given and shown to be consistent with the selected branch cut. At small wavenumbers, the kinetic mode properties typically start to deviate significantly from their fluid counterparts at beta approximately 0.5. At larger beta , there is no longer a consistent correspondence between the fluid and kinetic modes. Kinetic theory also dictates th }, keywords={ magnetosphere plasma waves magnetosphere plasma wave mode property low frequency wave kinetic theory Hall MHD ion-cyclotron wave phase velocity linear kinetic theory mode crossing classification dispersion two fluid theory Alfven wave magnetosonic mode }, mynotes={UNREAD}, }, @ARTICLE{KulkarniJan92, author={Kulkarni, V.H. and Das, J.H.}, title={ Very low frequency (VLF) chorus emissions: a topical survey }, journal={Surveys in Geophysics}, volume={13}, number={1}, year={1992}, month={Jan}, pages={35-46}, abstract={ Reviews the observations of natural VLF radio emission termed 'chorus', that have been made on the ground and abroad satellites, and also their dependence on various geomagnetic phenomena. The current theoretical interpretations of the generation and propagation of chorus signals are highlighted }, keywords={ atmospheric radiation magnetosphere reviews VLF radiowave emission magnetosphere chorus VLF radio emission generation propagation 3 to 30000 kHz }, mynotes={UNREAD}, }, @ARTICLE{LagoutteMay85, author={Lagoutte, D. and Lefeuvre, F.}, title={ Multispectral analysis for electromagnetic wave field components in a magnetoplasma: application to narrow-band VLF emissions }, journal={Journal of Geophysical Research}, volume={90}, number={A5}, year={1985}, month={May}, pages={4117-27}, abstract={ The multispectral analysis of the wave field components of an electromagnetic wave observed at a fixed point in a magnetoplasma is performed using a maximum entropy method. The validity of the analysis is a posteriori tested comparing the propagation characteristics of the waves, as derived from the spectral matrix estimates, to the propagation characteristics predicted by the magneto-ionic theory. The techniques so developed are applied to the analysis of ground-based transmitter signals observed on GEOS 1 }, keywords={ electromagnetic wave propagation in plasma ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation radiowave propagation EM wave ionosphere magnetosphere radiowave magnetoplasma narrow-band VLF emissions multispectral analysis maximum entropy method propagation characteristics spectral matrix estimates magneto-ionic theory GEOS 1 }, mynotes={UNREAD}, }, @ARTICLE{LagoutteJan89, author={Lagoutte, D. and Lefeuvre, F. and Hanasz, J.}, title={ Application of bicoherence analysis in study of wave interactions in space plasma }, journal={Journal of Geophysical Research}, volume={94}, number={A1}, year={1989}, month={Jan}, pages={435-42}, abstract={ A spectral analysis at the second order (power spectrum) loses the phase information among the different Fourier components. To retain this information, the bispectrum (third order) and/or the bicoherence (normalized bispectrum) are calculated. Application to simulated data, shows the dependence of the bispectrum to amplitudes of involved waves and of the bicoherence to signal-to-noise ratio. The bicoherence technique is applied in the analysis of harmonics produced gy an electronic receiver, as well as in the investigation of phase coherence between a ground-transmitter signal, a natural ELF emission near the proton gyrofrequency, and the sidebands around the carrier. Strong arguments are provided that the sidebands are generated by a parametric interaction between the transmitter signal and the ELF emission }, keywords={ ionosphere ionospheric electromagnetic wave propagation magnetosphere magnetospheric electromagnetic wave propagation plasma wave interaction radiowave ionosphere magnetosphere EM wave propagation wave wave interaction bicoherence analysis space plasma spectral analysis phase information bispectrum }, mynotes={UNREAD}, }, @ARTICLE{LairdJan81, title={ Reflection of electromagnetic waves by density gradients in a magnetised plasma }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={43}, number={1}, year={1981}, month={Jan}, pages={81-6}, abstract={ The reflection of electromagnetic waves by density gradient in a plasma with a magnetic field derived from a scalar potential is studied. Conditions are found for reflection at grazing incidence at a surface containing field lines. No restriction is placed on the angle between the wave-normal and the field, and account is taken of the curvature of the surface and the anisotropy of the medium. Particular reference is made by whistler-mode waves in the magnetosphere. The minimum electron density enhancement needed for reflection is calculated. Guidance by small-scale irregularities and 'super whistlers' (whistlers with upper cut-off above one-half the equatorial electron cyclotron frequency) are briefly discussed }, keywords={ electromagnetic wave propagation in plasma magnetospheric electromagnetic wave propagation whistlers density gradients magnetised plasma magnetic field scalar potential whistler-mode waves magnetosphere electron density super whistlers EM wave reflection }, mynotes={UNREAD}, }, @ARTICLE{LalmaniDec88, author={Lalmani, Kishen and K. and Khosa, P.N.}, title={ Low latitude discrete VLF chorus-an indicator of the wave-particle interactions in the inner magnetosphere }, journal={Indian Journal of Physics, Part B}, volume={62B}, number={4}, year={1988}, month={Dec}, pages={536-40}, abstract={ Discrete chorus emissions are very low frequency (VLF) electromagnetic waves that are commonly observed outside the plasmasphere. The authors present the analysis of the discrete chorus type emissions observed probably for the first time at low latitude and discuss their role as a diagnostic tool for studying the plasma processes in the inner magnetosphere. The discrete chorus emissions recorded during strong magnetic storm on 6-8 March, 1986 at the low latitude ground station Gulmarg (geomag. lat; 24 degrees 26'N) are selected for the present investigation }, keywords={ atmospherics magnetosphere magnetospheric electromagnetic wave propagation plasma plasma diagnostics AD 1986 03 06 to 08 atmospherics VLF chorus wave-particle interactions inner magnetosphere discrete chorus type emissions low latitude diagnostic tool plasma magnetic storm Gulmarg }, mynotes={UNREAD}, }, @ARTICLE{LalmaniJul96, author={Lalmani, Singh and R.P., Singh and R. and Ahmad, A.}, title={ Whistler observations of the quiet time plasmasphere-ionosphere coupling fluxes at low latitude }, journal={Earth, Moon, and Planets}, volume={74}, number={1}, year={1996}, month={Jul}, pages={7-15}, abstract={ Observations of whistlers during quiet times made at low-latitude ground station Nainital (geomag, lat. 19 degrees 1'N) are used to deduce plasmasphere-ionosphere coupling fluxes. The whistler data from 3 magnetically quiet days are presented that show a smooth decrease in dispersion with time. This decrease in dispersion is interpreted in terms of a corresponding decrease in electron content of tubes of ionization. The electron densities, electron tube contents (10/sup 16/ el/m/sup 2/-tube) and coupling fluxes (10 el m/sup -1/ s/sup -1/) are computed by means of an accurate curve fitting method developed by Tarcsai (1975) and are in good agreement with the results reported by other workers }, keywords={ atmospheric movements electron density ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation whistlers whistler observations quiet time plasmasphere-ionosphere coupling fluxes low latitude Nainital magnetically quiet days dispersion electron content ionization electron densities electron tube contents coupling fluxes curve fitting method }, mynotes={UNREAD}, }, @ARTICLE{LanzerottiDec75, author={Lanzerotti, L.J. and Fukunishi, H.}, title={ Relationships of the characteristics of magnetohydrodynamic waves to plasma density gradients in the vicinity of the plasmapause }, journal={Journal of Geophysical Research}, volume={80}, number={34}, year={1975}, month={Dec}, pages={4627-34}, abstract={ Top side electron density data obtained during the hours of approximately 2100-2400 LT from the ionosphere sounder on the Isis 2 satellite are used to give indications of possible latitude gradients in the magnetospheric plasma density distributions. Studies are made of the amplitude and polarization characteristics of magnetohydrodynamic waves that occur in the frequency range approximately 10-30 MHz at L approximately 3.2 to L approximately 4.4 during time intervals of Isis 2 passes. It is found that reversals in the sense of wave polarization occur in the vicinity of latitudes where L shell gradients are observed in the electron density distributions. These results give strong support to the importance of magnetosphere plasma density gradients and the plasmapause in coupling ULF driving energy sources to locally resonant magnetospheric field lines }, keywords={ electron density ionosphere magnetohydrodynamic waves magnetosphere plasma polarisation magnetohydrodynamic waves plasma density gradients ionosphere sounder Isis 2 satellite latitude gradients magnetospheric plasma density distributions amplitude ULF driving energy sources locally resonant magnetospheric field lines 10 to 30 MHz wave polarisation sense reversals plasmapause vicinity L-shell gradients top side electron density data energy sources field lines coupling }, mynotes={UNREAD}, }, @ARTICLE{LanzerottiDec72, author={Lanzerotti, L.J. and Hasegawa, A. and Tartaglia, N.A.}, title={ Morphology and interpretation of magnetospheric plasma waves at conjugate points during December solstice }, journal={Journal of Geophysical Research}, volume={77}, number={34}, year={1972}, month={Dec}, pages={6731-45}, abstract={ The morphological characteristics of magnetospheric plasma waves (period tau approximately 18 to 150 sec) detected at conjugate points near L=4 during the winter solstice are studied. No magnetospheric waves that satisfy an imposed strict selection criterion are observed after approximately 1700 LT. Approximately half the 94 accepted events are left-hand polarized. No significant change in the polarization characteristics of the waves is observed as a function of local time. Approximately 16% of the events have opposite polarizations in the two hemispheres. The morphological polarization characteristics are discussed in the context of expected body- and surface-wave polarizations }, keywords={ magnetosphere plasma waves magnetospheric plasma waves conjugate points December solstice morphological characteristics winter solstice polarization characteristics }, mynotes={UNREAD}, }, @ARTICLE{LarkinaJan89, author={Larkina, V.I. and Mineev, Yu.V. and Senchuro, I.N.}, title={ Wave-particle interactions in the Earth's radiation belts: data from Interkosmos-19 }, journal={Kosmicheske Issledovaniya}, volume={27}, number={1}, year={1989}, month={Jan}, pages={84-8}, abstract={ During geomagnetic disturbances during March and April 1979, the authors obtained simultaneous data on the following quantities at altitudes in the outer ionosphere: changes in the geomagnetic field, fluxes of electrons with energies in the range E/sub e/=0.1-2.0 MeV, and the intensities of the magnetic and electric components of the fields of low-frequency radiation at frequencies between 0.1 and 16 kHz. An increase in the electric component of the low-frequency radiation was accompanied by a reduction in the fluxes of energetic electrons with energies of about 1 MeV in the inner radiation belt. A spectral analysis of the simultaneous fluctuations has revealed several characteristic periods in the magnetic field, in the intensity of the low-frequency radiation, and in the fluxes of energetic electrons in the outer radiation belt }, keywords={ atmospheric electricity atmospherics electrons geomagnetic variations magnetic storms radiation belts geomagnetic field variations magnetic storms AD 1979 03 to 04 energetic electron fluxes magnetosphere energetic electron fluxes inner radiation belt electric field component magnetic field component EM radiation intensity wave-particle interactions Earth's radiation belts Interkosmos-19 geomagnetic disturbances outer ionosphere low-frequency radiation 0.1 to 2.0 MeV 584 to 876 km 186 to 1037 km 1.186 to 5.570 Earthradii }, mynotes={UNREAD}, }, @ARTICLE{LedleyOct71, title={ Magnetopause attitudes during Ogo 5 crossings }, journal={Journal of Geophysical Research}, volume={76}, number={28}, year={1971}, month={Oct}, pages={6736-42}, abstract={ The attitude of the magnetopause current layer is determined for 31 Ogo 5 crossings located at subsatellite local times between 0430 and 1020 and solar magnetospheric latitudes between -8.5 degrees and +40 degrees . A consistent difference in this attitude is observed between crossings in which the satellite leaves the magnetosphere and crossings in which it enters. The magnitude of this difference appears to be independent of the sun-earth-satellite angle. The ratio of the component of the magnetic field normal to the magnetopause to the total adjacent magnetospheric field is computed for each crossing. Ratios ranging from +0.1 to -0.2 are obtained where a plus sign signifies an outward directed component. The average ratio for those crossings in which the magnetosheath and magnetospheric fields subtended angles of greater than 90 degrees is -0.03+or-0.09 }, keywords={ artificial satellites magnetosphere magnetopause attitudes current layer crossings magnetic field magnetosheath Sun earth satellite angle }, mynotes={UNREAD}, }, @ARTICLE{LefeuvreJul85, author={Lefeuvre, F. and Helliwell, R.A.}, title={ Characterization of the sources of VLF hiss and chorus observed on GEOS 1 }, journal={Journal of Geophysical Research}, volume={90}, number={A7}, year={1985}, month={Jul}, pages={6419-38}, abstract={ Ray-tracing techniques are used to locate the apparent source regions of natural electromagnetic emissions observed on the GEOS 1 satellite and to determine the wave normal directions at this apparent source region. They are applied to VLF hiss, whose analysis in terms of the wave distribution function (WDF) has established that they often consisted of a sum of two or more very distinct wave packets at the point of observation. An example of a two-peaked WDF chorus is also examined. A two-dimensional ray-tracing program is used. It is shown theoretically that even if the exact location of the source region is difficult to estimate accurately, more precise information can still be obtained on the wave normal distribution at the source region. VLF hiss was generated in the vicinity of the equator at high wave normal angles }, keywords={ atmospheric radiation magnetosphere location radiowave emission magnetosphere sources VLF hiss chorus source regions natural electromagnetic emissions wave normal distribution }, mynotes={UNREAD}, }, @ARTICLE{LefeuvreMay83, author={Lefeuvre, F. and Lagoutte, D.}, title={ Bias for spectral density estimates of electromagnetic wave field components in a magnetoplasma }, journal={Annales Geophysicae}, volume={1}, number={3}, year={1983}, month={May}, pages={265-70}, abstract={ The auto- and cross-power spectral densities of the electric and magnetic components of an electromagnetic wave field propagating in a magnetoplasma can be related to a wave distribution function (WDF) that specifies how the wave energy density is distributed with respect to the wave-number vector K. Those relations are used to evaluate the bias errors of the power spectral density estimates of the field components. As an application the WDF is assumed to be constant over the frequency band of analysis and the waves are supposed to propagate in the whistler mode. Under these hypotheses the power spectral densities of the magnetic components are unbiased while the power spectral densities of the electric components are systematically biased }, keywords={ electromagnetic wave propagation in plasma ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation radiowave propagation magnetised plasma EM wave propagation atmosphere radiowave ionosphere magnetosphere spectral density estimates electromagnetic wave field magnetoplasma cross-power wave distribution function wave-number vector whistler mode }, mynotes={UNREAD}, }, @ARTICLE{LefeuvreAug82, author={Lefeuvre, F. and Neubert, T. and Parrot, M.}, title={ Wave normal directions and wave distribution functions for ground-based transmitter signals observed on GEOS 1 }, journal={Journal of Geophysical Research}, volume={87}, number={A8}, year={1982}, month={Aug}, pages={6203-17}, abstract={ VLF whistler mode pulses of approximately 1-s duration emitted by the omega navigation system transmitter located in Norway have been observed on-board the GEOS 1 satellite. The wave normal directions of 7 pulses have been determined by three different methods of analysis: the cross product method, Means' method, and the maximum entropy method of determination of the wave distribution function (WDF). The three methods and their solutions are compared and discussed in terms of the statistical properties of the signals (signal to noise ratio, stationarity in time, degree of polarization, ellipticity), and in terms of sensitivity to inconsistencies in the data. The wave normals are found to have angles approximately 130 degrees with the earth's magnetic field direction, pointing slightly eastward of the local magnetic meridian. They exhibit a time variation with a 0.2- to 0.4-s periodicity }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation radiowave propagation VLF radiowave propagation EM wave ionosphere magnetosphere wave distribution functions whistler mode wave normal directions }, mynotes={UNREAD}, }, @ARTICLE{LefeuvreApr81, author={Lefeuvre, F. and Parrot, M. and Delannoy, C.}, title={ Wave distribution functions estimation of VLF electromagnetic waves observed onboard Geos 1 }, journal={Journal of Geophysical Research}, volume={86}, number={A4}, year={1981}, month={Apr}, pages={2359-75}, abstract={ Two methods to determine the electromagnetic wave distribution function are presented. The first is based on the use of the Dirichlet kernels and provides a local average. It has the disadvantage, however, of a nonsystematic approach to positive solutions. The second uses the maximum entropy concept. It leads to particular solutions that are smooth and positive everywhere. The two methods are shown to be complementary. Applications to VLF electromagnetic waves observed onboard Geos 1 are discussed }, keywords={ magnetospheric electromagnetic wave propagation radiowave propagation EM waves magnetosphere geomagnetic field VLF Geos 1 wave distribution function Dirichlet kernels maximum entropy }, mynotes={UNREAD}, }, @ARTICLE{Lengyel-FreyJul94, author={Lengyel-Frey, D. and Farrell, W.M. and Stone, R.G. and Balogh, A. and Forsyth, R.}, title={ An analysis of whistler waves at interplanetary shocks }, journal={Journal of Geophysical Research}, volume={99}, number={A7}, year={1994}, month={Jul}, pages={13325-34}, abstract={ Presents an analysis of whistler wave magnetic and electric field amplitude ratio from which the authors compute wave propagation angles and energies of electrons in resonance with the waves. To do this analysis, they compute the theoretical dependence of ratios of wave components on the whistler wave propagation angle theta for various combinations of orthogonal wave components. Ratios of wave components that would be observed by a spinning spacecraft are determined, and the effects of arbitrary inclinations of the spacecraft to the ambient magnetic field and to the whistler wave vector are studied. The analysis clearly demonstrates that B/E, the ratio of magnetic to electric field amplitudes, cannot be assumed to be the wave index of refraction, contrary to assumptions of some earlier studies. Therefore previous interpretations of whistler wave observations based on this assumption must be reinvestigated. B/E ratios derived using three orthogonal wave components can be used to unambiguously determine theta . Using spin plane observations alone, a significant uncertainty occurs in the determination of theta . Nevertheless, for whistler waves observed downstream of several interplanetary shocks by the Ulysses plasma wave experiment the authors find that theta is highly oblique. They suggest that the analysis of wave amplitude ratios used in conjunction with traditional stability analyses provide a promising tool for determining which particle distributions and resonances are likely to be dominant contributors to wave growth }, keywords={ astrophysical plasma plasma shock waves solar wind whistlers whistler waves interplanetary shocks magnetic field electric field amplitude ratio wave propagation angles electrons resonance orthogonal wave components spinning spacecraft inclinations wave index of refraction spin plane observations downstream Ulysses plasma wave experiment stability analyses particle distributions wave growth }, mynotes={UNREAD}, }, @ARTICLE{LesterJun80, author={Lester, M. and Smith, A.J.}, title={ Whistler duct structure and formation }, journal={Planetary and Space Science}, volume={28}, number={6}, year={1980}, month={Jun}, pages={645-54}, abstract={ Whistler components received by the VLF goniometer at Halley, Antarctica, have been scaled for nose frequency and direction of arrival. The data were taken from two separate one hour periods on either side of local midnight (0023-0133 UT and 0340-0450 UT, 5 June 1975). Because of the high whistler occurrence rate at this time and the rapid processing facilitated by the Sheffield semi-automated whistler analyser, it has been possible to scale 1850 whistler components and hence obtain high resolution mapping of the whistler duct structure. The number of observable ducts increased from 4 at 0030 UT to about 15 at 0130 UT and had reached about 31 by 0400 UT. This increasing number of ducts, together with an observed clustering of ducts in the second one hour period, provides evidence for duct formation. The observations have been compared with the various duct generation mechanisms which have been proposed. The duct formation process may have been associated with a negative change in Dst which occurred at the same time, and this possibility is discussed }, keywords={ atmospheric structure electron density geomagnetic variations magnetic storms magnetospheric electromagnetic wave propagation whistlers VLF goniometer Antarctica nose frequency whistler occurrence rate duct generation mechanisms duct formation process magnetosphere whistler duct structure magnetosphere EM wave propagation Halley Base whistler arrival direction AD 1975 06 05 geomagnetic Dst index negative change magnetic storms electron density ducts }, mynotes={UNREAD}, }, @ARTICLE{Liang-BaixianAug85, author={Liang Baixian, Bao Zongti and Xu Jisheng}, title={ Propagation characteristics of night-time whistlers in the region of equatorial anomaly }, journal={J. Atmos. Terr. Phys. (UK), Journal of Atmospheric and Terrestrial Physics}, volume={47}, number={8-10}, year={1985}, month={Aug}, pages={999-1007}, abstract={ Results of simultaneous multi-station observations of night-time whistlers obtained at very low latitudes for the last three years are presented. The propagation mechanism of these whistlers is also discussed. Some records can be shown to have the characteristics of ducted propagation by calculating the dispersion of the whistlers along a ducted path and by noticing the feature of strong intensity, as well as the existence of three-hop echoes. Whistlers in some other records, however, can be shown to be propagating along a non-ducted path by numerical ray-tracing, in which a non-dipole field (IGRF) is used and a negative horizontal gradient of ionization in the equatorial ionosphere is taken into account. A definite whistler path seems to exist at very low latitudes. The effects of magnetic storms on the parameters of low latitude whistlers due to variations in the equatorial ionosphere are also discussed }, keywords={ ionosphere ionospheric electromagnetic wave propagation whistlers whistler propagation low latitude ionosphere magnetosphere characteristics night-time whistlers equatorial anomaly propagation mechanism ducted propagation whistler path }, mynotes={UNREAD}, }, @ARTICLE{LichtenbergerNov87, author={Lichtenberger, L. and Hamar, D. and Cserepes, L.}, title={ Computation of whistler wave normals using a combined matched filtering and parameter estimation technique }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={49}, number={11-12}, year={1987}, month={Nov}, pages={1075-9}, abstract={ A new method is presented for computing the wave normal directions of deterministic VLF signals that can be approximated by plane waves. The a priori information about the frequency-time behaviour of the signal is exploited by a matched filtering and subsequent parameter estimation technique. The method was developed basically to determine wave normal directions of whistlers from wave field components measured on-board. After an outline of the method, results obtained for simulated whistlers are presented that demonstrate the superiority of the new method over the cross-product and Means methods }, keywords={ magnetospheric electromagnetic wave propagation whistlers magnetosphere radiowave propagation whistler wave normals combined matched filtering parameter estimation wave normal directions deterministic VLF signals whistlers }, mynotes={UNREAD}, }, @ARTICLE{Likhter87, author={Likhter, Ya.I. and Larkina, V.I. and Jiricek, F. and Triska, P.}, title={ Intensity of VLF and ELF phenomena in the outer ionosphere }, journal={Studia Geophysica et Geodaetica}, volume={31}, number={1}, year={1987}, month={}, pages={85-91}, abstract={ Spatial and temporal variability of natural ELF-VLF phenomena field intensity has been studied using data from the Interkosmos satellites with apogees below 2000 km. The results show a distinct dependence of the diurnal variation and latitudinal intensity distribution on the magnetic activity. The L-value at which the maximum of plasmaspheric noise occurs, e.g. correlates better with the Dst-index than with other indices }, keywords={ atmospheric radiation ionosphere magnetosphere radiowave emission spatial variation magnetosphere ionospheric ELF noise VLF ELF outer ionosphere temporal variability intensity diurnal variation latitudinal intensity distribution magnetic activity L-value plasmaspheric noise }, mynotes={UNREAD}, }, @ARTICLE{LinMar91, author={Lin, N. and Engebretson, M.J. and McPherron, R.L. and Kivelson, M.G. and Baumjohann, W. and Luehr, H. and Potemra, T.A. and Anderson, B.J. and Zanetti, L.J.}, title={ A comparison of ULF fluctuations in the solar wind, magnetosheath, and dayside magnetosphere. 2. Field and plasma conditions in the magnetosheath }, journal={Journal of Geophysical Research}, volume={96}, number={A3}, year={1991}, month={Mar}, pages={3455-64}, abstract={ For pt.1 see ibid., vol.96, no.A3, p.3441-54 (1991). Data from three spacecraft (AMPTE IRM, AMPTE CCE, and ISEE 1 or 2) are used to study the correlation among the field and plasma conditions in the subsolar magnetosheath region, ULF wave activity in the magnetosphere, and the cone angle of the IMF. A disturbance parameter, R, which is the magnitude of the normalized resultant of unit vectors is used to describe the disturbance of the magnetosheath region. A 'quiet' state has R values close to unity. The authors have studied five time intervals and found that when the R values of the magnetosheath magnetic field were below 0.8, indicative of a disturbed magnetosheath near local noon, transverse harmonic oscillations of magnetic field lines in the Pc 3, 4 range were observed in the magnetosphere and small cone angles were observed in the solar wind }, keywords={ magnetosphere solar wind solar wind magnetosphere interaction micropulsation AD 1984 AD 1985 Pc 3 Pc 4 ULF fluctuations magnetosheath dayside magnetosphere plasma conditions subsolar ULF wave activity cone angle IMF magnetic field disturbed }, mynotes={UNREAD}, }, @ARTICLE{LoisierMar79, author={Loisier, G. and Cornilleau-Wehrlin, N. and Gendrin, R.}, title={ Determination of wave normal directions for time-varying signals. Application to natural VLF emissions detected on board satellite }, journal={Annales des Telecommunications}, volume={34}, number={3-4}, year={1979}, month={Mar}, pages={214-19}, abstract={ A method for studying the polarization of an electromagnetic plane wave, the characteristics of which vary rapidly in time, is described. This method is based upon the concept of the (instantaneous) complex representation of a polarized signal. It is possible in particular to yield the wave normal direction as a function of both time and frequency. The accuracy of the method is studied, as a function of both the signal-to-noise ratio and of the eccentricity of the polarization ellipse. This method is applied to the determination of wave normal directions of natural VLF signals propagating in the whistler mode within the magnetosphere. Important variations in the propagation characteristics of the signals are evidenced }, keywords={ atmospherics magnetospheric electromagnetic wave propagation polarisation radio direction-finding radiowave propagation signal detection whistlers complex representation wave normal direction eccentricity polarization ellipse VLF signals whistler mode magnetosphere propagation characteristics electromagnetic plane wave polarisation signal to noise ratio }, mynotes={UNREAD}, }, @ARTICLE{LouarnMar96, author={Louarn, P. and Le Queau, D.}, title={ Generation of the auroral kilometric radiation in plasma cavities. I. Experimental study }, journal={Planetary and Space Science}, volume={44}, number={3}, year={1996}, month={Mar}, pages={199-210}, abstract={ From Viking observations, auroral kilometric radiation (AKR) comes from plasma cavities, filled by a hot and tenuous plasma, separated from the denser and colder external plasma by sharp density gradients. These plasma inhomogeneities constitute interfaces that affect the wave propagation and then could play an important role in the generation of the radiation. These effects on the propagation are analyzed using Viking measurements obtained during crossings of AKR sources. It is shown that the electromagnetic energy, generated on the X mode, in the close vicinity of the local electron gyrofrequency, is first confined inside the cavity structure. Indeed, in a small frequency domain that extends a few kHz above the local electron gyrofrequency the "internal" X mode waves can only be connected to "external" Z or O mode waves. The corresponding transmission coefficients are measured as being an attenuation larger than 25 dB. At higher frequencies, the internal waves are connected to the external X mode with a transmission coefficient close to 1. However, this connection is only possible after an upward propagation of the electromagnetic energy inside the source. The progressive rotation of the wave vector associated to the wave vector associated to the wave refraction is estimated. An analysis of the polarization also shows that the radiating diagram likely does not have a cylindrical symmetry with respect to the geomagnetic field: the radiation is mainly emitted tangentially to the laminar structure constituted by the source. The existence of a preferential direction in the radiating diagram is a direct observable consequence of the finite extension of the sources }, keywords={ atmospheric radiation magnetosphere magnetospheric electromagnetic wave propagation plasma radiowave propagation auroral kilometric radiation plasma cavities Viking Sweden observations plasma inhomogeneities interfaces wave propagation AKR sources cavity structure Z mode waves O mode waves X mode waves transmission coefficients attenuation internal waves 25 dB }, mynotes={UNREAD}, }, @ARTICLE{LouarnMay90, author={Louarn, P. and Roux, A. and de Feraudy, H. and Le Queau, D. and Andre, M. and Matson, L.}, title={ Trapped electrons as a free energy source for the auroral kilometric radiation }, journal={Journal of Geophysical Research}, volume={95}, number={A5}, year={1990}, month={May}, pages={5983-95, 6115-16}, abstract={ Simultaneous measurements of electromagnetic fields and particle distributions, measured during the crossing by the Swedish spacecraft Viking of an auroral kilometric radiation (AKR) source, are presented. It is shown that AKR is generated within an acceleration region characterized by an upward directed parallel electric field, as evidenced by its signature on the proton and electron distributions. From particle observations inside the AKR source it is clear that the potential drop below the spacecraft produces upward moving field-aligned ion beams and a depletion in the density of low energy electrons. The potential drop above the spacecraft products downward accelerated electrons. A large fraction of these electrons have small parallel velocities; they mirror above the ionosphere. These trapped electrons lie in a region of velocity space which should be empty in a simple adiabatic theory. The authors suggest that these electrons get trapped when they experience a time-varying (or space-varying) parallel electric field. This conclusion is supported by the comparison between the observed electron distribution function and a model distribution function built by applying Liouville theorem }, keywords={ atmospheric radiation magnetosphere time varying electric field trapped electrons magnetosphere AKR EM emission LF radiowave emission generation mechanism free energy source auroral kilometric radiation Viking }, mynotes={UNREAD}, }, @ARTICLE{LudlowNov89, title={ Growth of obliquely propagating ion cyclotron waves in the magnetosphere }, journal={Journal of Geophysical Research}, volume={94}, number={A11}, year={1989}, month={Nov}, pages={15385-91}, abstract={ Presents linear growth rate calculations of electromagnetic ion cyclotron waves driven by hot anisotropic protons in a magnetized plasma. The angle between the wave vector and the magnetic field is arbitrary. This introduces Landau damping by the thermal electrons, an effect not present for strictly parallel propagation. The model contains concentrations of O/sup +/ and H/sup +/ as well as H/sup +/, with densities and temperatures typical of ion cyclotron wave generation regions inside the plasmasphere around L=3. The behavior of growth regions in k space is studied. Although the growth rates peak at theta =0 degrees , they do not depend strongly on theta for theta <30 degrees . At large wave normal angles, weak peaks in wave growth are found with much smaller growth rates than at 0 degrees }, keywords={ magnetosphere plasma plasma waves plasma wave propagation oblique propagation EM ion cyclotron wave magnetosphere linear growth rate calculations electromagnetic ion cyclotron waves hot anisotropic protons magnetized plasma Landau damping plasmasphere }, mynotes={UNREAD}, }, @ARTICLE{LuetteJul77, author={Luette, J.P. and Park, C.G. and Helliwell, R.A.}, title={ Longitudinal variations of very-low-frequency chorus activity in the magnetosphere: evidence of excitation by electrical power transmission lines }, journal={Geophysical Research Letters}, volume={4}, number={7}, year={1977}, month={Jul}, pages={275-8}, abstract={ Very-low-frequency (VLF) chorus activity detected by the Ogo 3 satellite has the highest probability of occurrence in regions threaded by geomagnetic field lines that intersect industrialized areas. Interpretation of these results is based on radiated power line harmonics that leak into the magnetosphere and stimulate the recorded emissions through cyclotron interaction with trapped energetic electrons. These results emphasize the need for a careful evaluation of the effects of man-made VLF noise on the ionosphere and magnetosphere }, keywords={ atmospherics magnetosphere power overhead lines electrical power transmission lines Ogo 3 satellite radiated power line harmonics magnetosphere cyclotron interaction trapped energetic electrons VLF chorus }, mynotes={UNREAD}, }, @ARTICLE{LundinJan97, author={Lundin, B. and Krafft, C.}, title={ On the focusing of whistler wave field intensity in the quasi-resonant propagation regime }, journal={Journal of Geophysical Research}, volume={102}, number={A1}, year={1997}, month={Jan}, pages={141-50}, abstract={ The propagation of whistler mode wave packets in a cold magnetospheric plasma is investigated in the quasi-resonant regime (near the oblique lower hybrid resonance) using the ray approximation. The analysis is essentially simplified by introducing a special curvilinear orthogonal coordinate system (resonant coordinate system (RCS)), which is naturally adapted to the description of the propagation of quasi-electrostatic waves in a cold plasma, when the group velocity and the wave vector tend to be orthogonal to each other in the deep quasi-electrostatic limit. It is shown that in an overdense plasma of the Earth plasmasphere, the parameters of the RCS are independent of the space density distribution of the background plasma. The general expressions for the Hamiltonian and whistler wave field intensity focusing law in a deep quasi-resonant regime are derived }, keywords={ magnetospheric electromagnetic wave propagation radiowave propagation whistlers focusing whistler wave field intensity quasi-resonant propagation regime cold magnetospheric plasma quasi-resonant regime oblique lower hybrid resonance ray approximation curvilinear orthogonal coordinate system resonant coordinate system quasi-electrostatic waves group velocity wave vector quasi-electrostatic limit overdense plasma Earth plasmasphere space density distribution background plasma Hamiltonian }, mynotes={UNREAD}, }, @ARTICLE{LyonsApr72, author={Lyons, L.R. and Kennel, C.F.}, title={ Formation of the slot between the inner and outer electron radiation belts }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={53}, number={4}, year={1972}, month={Apr}, pages={485}, abstract={ The pitch-angle diffusion of radiation belt electrons resulting from resonant interactions with the observed plasma-spheric whistler-mode wave band is quantitatively investigated. The effects of wave propagation obliquely to the geomagnetic field direction with the resulting diffusion at all cyclotron harmonic resonances and the Landau resonances are evaluated along with the effects of interactions occurring at all geomagnetic latitudes. The results account for the long term stability of the inner radiation zone, the location of its outer edge as a function of electron energy, and the removal of electrons at all energies to levels near zero throughout the slot. Computed pitch-angle distributions and precipitation decay rates are in good agreement with slot-region observations }, keywords={ plasma radiation belts formation of the slot radiation belt electrons resonant interactions wave propagation geomagnetic field direction cyclotron harmonic resonances Landau resonances long term stability of the inner radiation zone precipitation decay rates pitch angle diffusion plasmaspheric whistler mode wave band }, mynotes={UNREAD}, }, @ARTICLE{LyonsDec71, author={Lyons, L.R. and Thorne, R.M. and Kennel, C.F.}, title={ Electron pitch-angle diffusion driven by oblique whistler-mode turbulence }, journal={Journal of Plasma Physics}, volume={6}, number={}, year={1971}, month={Dec}, pages={589-606}, abstract={ A general description of cyclotron harmonic resonant pitch-angle scattering is presented. Quasi-linear diffusion coefficients are prescribed in terms of the wave normal distribution of plasma wave energy. Numerical computations are performed for the specific case of relativistic electrons interacting with a band of low frequency whistler-mode turbulence. A parametric treatment of the wave energy distribution permits normalized diffusion coefficients to be presented graphically solely as a function of the electron pitch-angle. The diffusion coefficients generally decrease with increasing cyclotron harmonic number. Higher harmonic diffusion is insignificant at very small electron pitch- angles, but becomes increasingly important as the pitch- angle increases. One thus expected the rate of pitch- angle scattering to decrease with increasing electron energy, since the resonant value of the latter varies proportionately with harmonic number. This indicates that, in mirror-type magnet field geometrics, such as the Earth's radiation belts, the diffusion losses of high energy electrons are likely to be appreciably slower than those at low energy. Integration of the diffusion rates along a complete bounce orbit will be required to clarify this point, however, since the high-energy particles will be subject to more rapid first harmonic diffusion near their mirror points }, keywords={ plasma transport processes turbulence wave normal distribution plasma wave energy relativistic electrons wave energy distribution normalized diffusion coefficients high energy electrons bounce orbit cyclotron harmonic resonant pitch angle scattering electron pitch angle diffusion oblique whistler mode turbulence quasi linear diffusion coefficients mirror type magnetic field geometrics Earth's radiation belts }, mynotes={UNREAD}, }, @ARTICLE{LyonsAug74, title={ General relations for resonant particle diffusion in pitch angle and energy }, journal={Journal of Plasma Physics}, volume={12}, number={}, year={1974}, month={Aug}, pages={45-9}, abstract={ By applying quasi-linear diffusion theory, general expressions are obtained for particle diffusion coefficients in both pitch angle and energy. The results are valid for resonant interactions with any mode of weak plasma turbulence, with wave energy distributed over any range of frequencies and wave normal angles. Simple relations are found between the diffusion coefficients, these relations reflecting the geometry of the diffusion surfaces for resonant particles }, keywords={ plasma transport processes plasma turbulence resonant particle diffusion pitch angle energy weak plasma turbulence }, mynotes={UNREAD}, }, @ARTICLE{MarquisFeb87, author={Marquis, E. and Teichmann, J.}, title={ Side-band instabilities of a steady finite-amplitude whistler wave in a collisionless plasma }, journal={Canadian Journal of Physics}, volume={65}, number={2}, year={1987}, month={Feb}, pages={173-84}, abstract={ The stability of a steady finite-amplitude whistler wave penetrating a collisionless, unbounded, homogeneous plasma is studied. The supporting wave as well as the excited side-band waves are assumed to propagate parallel to a uniform magnetostatic field B/sub 0/. For a general form of the distribution function of trapped electrons, the growth (damping) rates of side-band modes are calculated. It is shown that a particular distribution of trapped electrons gives rise to strongly unstable side-band electromagnetic modes having right-hand polarization. The spectrum of unstable electrostatic and electromagnetic satellite waves is analyzed }, keywords={ plasma instability plasma waves electrostatic satellite waves steady finite-amplitude whistler wave collisionless plasma supporting wave excited side-band waves uniform magnetostatic field distribution function trapped electrons right-hand polarization electromagnetic satellite waves }, mynotes={UNREAD}, }, @ARTICLE{Matsumoto83, author={Matsumoto, H. and Omura, Y.}, title={ Computer simulation studies of VLF triggered emissions deformation of distribution function by trapping and detrapping }, journal={Geophys. Res. Lett. (USA), Geophysical Research Letters}, volume={10}, number={8}, year={1983}, month={}, pages={607-10}, abstract={ A simulation study of VLF triggered emissions has been carried out in order to investigate quantitative changes of the velocity distribution function of resonant electrons caused by a combined action of nonlinear phase-trapping and geomagnetic inhomogeneity. It is a counterpart of the analytic theory proposed by Roux and Pellat (1978) }, keywords={ atmospheric radiation electrons radiation belts computer simulation radiation belts detrapping VLF triggered emissions velocity distribution function resonant electrons nonlinear phase-trapping geomagnetic inhomogeneity }, mynotes={UNREAD}, }, @ARTICLE{MeansOct72, title={ Use of the three-dimensional covariance matrix in analyzing the polarization properties of plane waves }, journal={Journal of Geophysical Research}, volume={77}, number={28}, year={1972}, month={Oct}, pages={5551-9}, abstract={ A technique for analyzing the polarization properties of plane waves that offers a number of advantages over methods currently used in the analysis of both ground and satellite observations of waves is developed. This technique reduces the computations required to find the wave normal vector, is less sensitive to common noise sources, and is amenable to analog implementation. The technique here is applied specifically to the analysis of a proton whistler, but it can also be used in most studies of ULF, ELF, and VLF magnetic-wave phenomena }, keywords={ geophysics magnetohydrodynamic waves protons waves whistlers three dimensional covariance matrix ULF magnetic wave phenomena ELF magnetic wave phenomena VLF magnetic wave phenomena polarisation properties plane waves wave normal vector proton whistler }, mynotes={UNREAD}, }, @ARTICLE{MellottAug85, author={Mellott, M.M. and Huff, R.L. and Gurnett, D.A.}, title={ The auroral kilometric radiation: DE 1 direction finding studies }, journal={Geophysical Research Letters}, volume={12}, number={8}, year={1985}, month={Aug}, pages={479-82}, abstract={ The authors have determined the directions of arrival of auroral kilometric radiation during three separate intervals using data from the DE 1 plasma wave instrument. In the case of the dominant extraordinary mode component, these directions were consistent with generation at the local electron cyclotron frequency on nightside auroral field lines. The ordinary mode component appeared to have a similar source in one case, but in other cases came from different directions. These other cases were consistent with reflection at the plasmapause and the wall of the auroral plasma cavity }, keywords={ atmospheric radiation atmospherics magnetosphere magnetospheric electromagnetic wave propagation plasma magnetosphere EM wave propagation VLF atmospherics atmospheric radiation EM wave source region AKR generation plasmapause reflection plasma cavity wall reflection Earth radio 0002 to 0004 reflection geometrics magnetosphere evening sector auroral kilometric radiation DE 1 direction finding studies DE 1 plasma wave instrument extraordinary mode component local electron cyclotron frequency nightside auroral field lines ordinary mode component auroral plasma cavity }, mynotes={UNREAD}, }, @ARTICLE{MolvigJun88, author={Molvig, K. and Hilfer, G. and Miller, R.H. and Myczkowski, J.}, title={ Self-consistent theory of triggered whistler emissions }, journal={Journal of Geophysical Research}, volume={93}, number={A6}, year={1988}, month={Jun}, pages={5665-83}, abstract={ A kinetic theory of triggered VLF whistler emissions is given that is capable of predicting from a small-scale numerical implementation the observed emission forms and frequency-time characteristics. The paper focuses on the theoretical developments and the explanation of the triggering process, complete with a demonstration of the threshold behavior (sometimes known as the dot-dash anomaly) and the generation of specific falling frequency emissions. The theory is a fully self-consistent nonlinear treatment based on kinetic theory and valid in the asymptotic limit when several trapping periods occur within the interaction region. Most of the features of the emission process can be determined analytically, such as the rate of change of frequency, related to magnetospheric parameters. For more quantitative predictions, such as predictions of amplitude and frequency waveforms a small numerical code which integrates the nonlinear wave equations is used }, keywords={ atmospheric radiation magnetosphere magnetospheric electromagnetic wave propagation whistlers whistler triggering process input wave magnetic field amplitude waveforms resonant particles trapping time whistler signal gain magnetosphere EM wave propagation wave-particle interactions trigger pulse duration trapped particles perpendicular velocities kinetic theory triggered VLF whistler emissions small-scale numerical implementation emission forms frequency-time characteristics threshold behavior dot-dash anomaly falling frequency emissions fully self-consistent nonlinear treatment asymptotic limit trapping periods interaction region magnetospheric parameters frequency waveforms small numerical code 5.5 kHz 100 ms }, mynotes={UNREAD}, }, @ARTICLE{MoorcroftMay84, title={ Propagation of plasma wave energy in the auroral E-region }, journal={Journal of Geophysical Research}, volume={89}, number={A5}, year={1984}, month={May}, pages={2963-70}, abstract={ The propagation of electrostatic plasma wave energy in the auroral E region has been studied using fluid theory. Typically, a wave travels at high speed nearly parallel to the magnetic field, except possibly for a small height interval where it is reflected upward; throughout, the direction of the propagation vector remains virtually unchanged and nearly perpendicular to the magnetic field. If k makes an angle of more than 0.25 degrees with the magnetic field, the wave passes through the E region without reflection. Kinks in the magnetic field lines (due to auroral currents) may lead to trapping of waves in layers less than 1 km thick. Secondary irregularities may be limited in both horizontal and vertical extent because of their motion relative to the primary waves on which they depend for growth. The processes determining the amplitude of irregularities have also been considered }, keywords={ E-region plasma ionosphere auroral E-region electrostatic plasma wave fluid theory magnetic field propagation auroral currents trapping primary waves }, mynotes={UNREAD}, }, @ARTICLE{Morioka90, author={Morioka, A. and Oya, H. and Kobayashi, K.}, title={ Polarization and mode identification of auroral kilometric radiation by PWS system onboard the Akebono (EXOS-D) satellite }, journal={Journal of Geomagnetism and Geoelectricity}, volume={42}, number={4}, year={1990}, month={}, pages={443-58}, abstract={ The first study of the Poynting flux of the auroral kilometric radiation (AKR) based on detected amplitudes and phase angle of waveforms has been carried out by the PWS (Plasma Waves and Sounder Experiment) onboard the Akebono satellite. The propagation mode of the AKR was determined. The first results of the Poynting vector indicated that there is a case where the medium intensity AKR shows L-O mode propagation. The sudden polarization reversal from the L-O mode to the R-X mode is associated with explosive AKR bursts. The electrostatic plasma waves were found near the local upper hybrid frequency in the source region }, keywords={ artificial satellites atmospheric radiation electromagnetic wave polarisation magnetosphere radiowave propagation mode identification magnetosphere explosive bursts auroral kilometric radiation EXOS-D Poynting flux amplitudes phase angle waveforms Plasma Waves and Sounder Experiment Akebono satellite propagation mode sudden polarization reversal electrostatic plasma waves source region }, mynotes={UNREAD}, }, @ARTICLE{MotschmannOct96, author={Motschmann, U. and Woodward, T.I. and Glassmeier, K.-H. and Southwood, D.J.}, title={ Wave field analysis by magnetic measurements at satellite arrays: generalized minimum variance analysis }, journal={Adv. Space Res. (UK), Advances in Space Research}, volume={18}, number={8}, year={1996}, month={Oct}, pages={315-19}, abstract={ The main goal of the CLUSTER mission with four identical spacecraft is the spatial resolution of plasma structures. For the determination of the wave vectors of a wave field from four positions classical Fourier analysis is inappropriate. We develop a generalized minimum variance technique which gives a high wave vector resolution though the spatial grid is restricted to only a few sampling positions. This technique uses the amplitude and phase information of the magnetic field from the four satellite positions and determines the optimum wave field corresponding to the measured data. The divergence-free nature of the magnetic field is used as a constraint. Using the magnetic data measured at four positions up to four different wave vectors at one frequency can be uniquely resolved }, keywords={ atmospheric techniques magnetosphere wave analysers magnetosphere artificial satellites wave fields generalized minimum variance analysis spatial resolution wave propagation magnetic field wave vectors covariance matrix coherent structures turbulence spectral energy density }, mynotes={UNREAD}, }, @ARTICLE{MourenasAug93, author={Mourenas, D. and Krasnosel'skikh, V.}, title={ A numerical study of instabilities producing auroral broadband electrostatic bursts }, journal={Annales Geophysicae}, volume={11}, number={8}, year={1993}, month={Aug}, pages={711-16}, abstract={ Intense broadband electrostatic noise (BEN) has been observed on many occasions by the VIKING satellite in the dayside as well as in the nightside auroral zones, correlated with multiple energetic electron beams registered by onboard particle analyzers. Using a modified version of the WHAMP program, the authors conduct a numerical study of the linear dispersion properties of waves in such a plasma. The results show that many BEN features, such as its extension well above f/sub pe/ (in the case when gyrofrequency is larger than plasma frequency), its relatively isotropic angular distribution, and the large wave amplitude in the low-frequency range of the analyzer, might be explained by linear interaction between low-temperature high-directed velocity beams and a higher density cold-cool background plasma }, keywords={ atmospheric radiation ionosphere plasma instability ionosphere radiowave propagation instabilities numerical model auroral broadband electrostatic burst BEN broadband electrostatic noise multiple energetic electron beams WHAMP linear dispersion low-temperature high-directed velocity beam cool background plasma plasma instability }, mynotes={UNREAD}, }, @ARTICLE{MutoJul87, author={Muto, H. and Hayakawa, M. and Parrot, M. and Lefeuvre, F.}, title={ Direction finding of half-gyrofrequency VLF emissions in the off-equatorial region of the magnetosphere and their generation and propagation }, journal={Journal of Geophysical Research}, volume={92}, number={A7}, year={1987}, month={Jul}, pages={7538-50}, abstract={ The spectra of VLF/ELF emissions in the off-equatorial region in the outer magnetosphere are, on occasion, found to consist of upper and lower bands with a frequency gap between them. The wave normal directions of the upper band VLF emissions have been determined by means of wave distribution function analyses based first on the measurement of three magnetic field components only, and then with the additional use of an electric field component. It is found that the wave distribution functions are composed of two peaks whose central wave normal angles theta with respect to the magnetic field at a geomagnetic latitude of approximately 17 degrees are close to the local oblique resonance cone theta /sub res/ but whose values of theta are always about 15-20 degrees less than theta /sub res/ at a higher latitude of approximately 26 degrees . The upper band of VLF emissions are identified as being 'half-gyrofrequency' VLF emissions generated in the vicinity of the magnetic equator, with their wave normals close to theta /sub res/. The characteristics of propagation between the equatorial source region and the observing positions have been investigated by direct ray tracing. The generation mechanism is also discussed }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation direct finding radiowave emission half-gyrofrequency VLF emissions off-equatorial region magnetosphere generation propagation outer magnetosphere wave normal directions upper band VLF wave distribution functions }, mynotes={UNREAD}, }, @ARTICLE{NagaiJul85, author={Nagai, T. and Horwitz, J.L. and Anderson, R.R. and Chappell, C.R.}, title={ Structure of the plasmapause from ISEE 1 low-energy ion and plasma wave observations }, journal={Journal of Geophysical Research}, volume={90}, number={A7}, year={1985}, month={Jul}, pages={6622-6}, abstract={ Low-energy ion pitch angle distributions are compared with plasma density profiles in the near-Earth magnetosphere using ISEE 1 observations. The classical plasma pause determined by the sharp density gradient is not always observed in the dayside region, whereas there almost always exists the ion pitch angle distribution transition from cold, isotropic to warm, bidirectional, field-aligned distributions. In the nightside region the plasmapause density gradient is typically found, and it normally coincides with the ion pitch angle distribution transition. The sunward motion of the plasma is found to the outer part of the 'plasmaspheric' plasma in the dusk bulge region }, keywords={ ionosphere magnetosphere ionosphere magnetosphere structure plasmasphere plasmapause low-energy ion plasma wave pitch angle distributions plasma density profiles dayside nightside motion }, mynotes={UNREAD}, }, @ARTICLE{NaganoDec94, author={Nagano, I. and Yagitani, S. and Kojima, H. and Kakehi, Y. and Shiozaki, T. and Matsumoto, H. and Hashimoto, K. and Okada, T. and Kokubun, S. and Yamamoto, T.}, title={ Wave form analysis of the continuum radiation observed by GEOTAIL }, journal={Geophysical Research Letters}, volume={21}, number={25}, year={1994}, month={Dec}, pages={2911-14}, abstract={ The Plasma Wave Instrument (PWI) onboard the GEOTAIL spacecraft has frequently observed continuum radiation (CR) throughout the geomagnetic tail region, including the magnetosheath (MS), the lobe, the plasma sheet boundary layer (PSBL), and the plasma sheet (PS). In addition to the usual escaping CR (from 10 kHz to 30 kHz) and the trapped CR (from about 5 kHz to 10 kHz), CR with the frequency structure extending down to 1 kHz (the local plasma frequency) has often been observed in the lobe region. Waveforms of the electric field in the frequency range less than 4 kHz, which is acquired by wave form capture in the PWI, are used to analyze in detail the frequency-time structure of such low-frequency CR near the lower cutoff. Two distinct cutoff frequencies modulated by the antenna spinning indicates that the CR in the lobe region propagates both in the O mode and in the X mode almost perpendicular to the earthward geomagnetic field line. The CR in the lobe region, especially in the vicinity of the PSBL, is sometimes accompanied by intense electrostatic electron-cyclotron-harmonic (ECH) (n+1/2) waves. These suggest that such a low-frequency CR in the distant tail region is most likely to be generated from the ECH waves near the PSBL, and trapped within the lobe between the PSBL and the MS }, keywords={ magnetosphere magnetosphere radiowave emission magnetotail wave form analysis continuum radiation GEOTAIL Geotail magnetic tail magnetosheath lobe, plasma sheet boundary layer VLF electrostatic electron-cyclotron-harmonic wave plasma wave 5 to 30 kHz }, mynotes={UNREAD}, }, @ARTICLE{NakamuraJan89, author={Nakamura, Y. and Ohdoh, T.}, title={ Whistler-triggered emissions observed by ISIS satellites }, journal={J. Geophys. Res. (USA), Journal of Geophysical Research}, volume={94}, number={A1}, year={1989}, month={Jan}, pages={89-92}, abstract={ VLF emissions triggered by whistlers are often observed at middle and high latitudes in the topside ionosphere by ISIS satellites. Most of them are so-called LHR emissions lasting for a few seconds. Latitudinal distributions of the occurrence rate for the whistler-triggered emissions in the topside ionosphere have been obtained by using VLF electric field data (50 Hz to 30 kHz) received from the ISIS 1 and 2 satellites at Kashima station, Communications Research Laboratory, Japan. These VLF emissions are classified into two groups according to the type of whistlers. The latitudinal distribution of the occurrence rate for emissions triggered by ducted whistlers is considerably different from that for emissions triggered by nonducted whistlers, especially at high latitudes. The occurrence rate for the emissions by nonducted whistlers is distributed rather randomly in latitude between L=2.0 and L=4.2. Further occurrence statistics data are presented }, keywords={ ionosphere magnetosphere magnetosphere whistler triggered emission VLF radiowave emission latitude distribution topside ionosphere LHR emissions occurrence 50 to 30000 Hz }, mynotes={UNREAD}, }, @ARTICLE{NakamuraDec87, author={Nakamura, Y. and Ondoh, T.}, title={ Observation of the magnetosphere and ionosphere by Dynamics Explorer satellite. VIII. Whistler triggered emissions observed by DE-1 and ISIS satellites }, journal={Review of the Radio Research Laboratories}, volume={33}, number={169}, year={1987}, month={Dec}, pages={255-61}, abstract={ For pt.VII see ibid., vol.33, no.169, p.245 (1987). VLF emissions triggered by whistlers are often observed at mid- and high-latitudes by DE-1 and ISIS satellites. Most of these emissions are LHR emissions which are triggered for a few seconds like a flag after a whistler near the lower hybrid resonance frequency. Characteristics of whistler-triggered emissions are analysed using the DE-1, ISIS-1 and -2 VLF electric field data received at Kashima station, RRL, Japan. Ducted and nonducted whistlers are discussed, and the observations made are considered }, keywords={ artificial satellites atmospheric electricity atmospherics ionosphere ionospheric electromagnetic wave propagation magnetosphere magnetospheric electromagnetic wave propagation plasma waves satellite links whistlers ducted whistlers magnetosphere ionosphere Dynamics Explorer satellite VLF emissions DE-1 ISIS satellites LHR emissions lower hybrid resonance frequency whistler-triggered emissions VLF electric field data Kashima station nonducted whistlers 0 to 10 kHz }, mynotes={UNREAD}, }, @ARTICLE{NishinoNov87, author={Nishino, M. and Tanaka, Y. and Katoh, Y.}, title={ Detection of the whistler-mode signals from VLF transmitter and their intensity characteristics }, journal={Transactions of the Institute of Electronics, Information and CommunicationEngineers B}, volume={J70B}, number={11}, year={1987}, month={Nov}, pages={1400-6}, abstract={ Radio signals from the VLF transmitter in Eastern USSR were observed at the conjugate point (geomagnetic latitude 40.2 degrees S) in South Australia, and the whistler-mode signals were detected by the measurements of the wave polarization and the propagation time from the transmitter. The intensity of the whistler-mode signals increased usually at sunset and sunrise, and it was moderate during the night. A high correlation was found between the occurrence probability of the whistler-mode signals and the occurrence of whistlers, which may suggest that the occurrence of whistlers is controlled predominantly by propagation conditions }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation radiowave propagation signal detection whistlers very low frequency radio signal detection signal increase magnetospheric EM wave propagation ionospheric EM wave propagation radiowaves whistler-mode signals VLF transmitter intensity characteristics Eastern USSR conjugate point geomagnetic latitude 40.2 degrees S South Australia wave polarization propagation time sunset sunrise occurrence probability propagation conditions }, mynotes={UNREAD}, }, @ARTICLE{NorthropApr72, author={Northrop, T.G. and Holzer, R.E. and Olson, J.V. and Russell, C.T.}, title={ A study of waves in the Earth's bow shock }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={53}, number={4}, year={1972}, month={Apr}, pages={487}, abstract={ The perturbation vectors of waves up and downstream from the region of maximum compression in the bow shock were examined on OGO-5 under particularly steady solar wind conditions. The polarization of the upstream waves was RH, circular and of the downstream waves LH, elliptical in the spacecraft frame. By observing that the polarization of the waves remained unchanged as the shock motion swept the wave structure back and forth across the the satellite three times in 8 minutes, it was found that the waves were not stationary in the shock frame. A study of the methods of determining the shock normal indicates that the normal estimated from a shock model should be superior to one based upon magnetic coplanartiy. The propagation vectors of the waves examined did not coincide with the shock model normal, the average magnetic field, or the plasma flow velocity. However, the major axis of the polarization ellipse of the downstream wave was nearly parallel to the upstream propagation vector }, keywords={ magnetosphere shock waves waves Earth's bow shock perturbation vectors region of maximum compression steady solar wind polarization magnetic coplanarity average magnetic field plasma flow velocity }, mynotes={UNREAD}, }, @ARTICLE{NunnSep91, author={Nunn, D. and Sazhin, S.S.}, title={ On the generation mechanism of hiss-triggered chorus }, journal={Annales Geophysicae. Atmospheres, Hydrospheres and Space Sciences}, volume={9}, number={9}, year={1991}, month={Sep}, pages={603-13}, abstract={ A theory is presented of the generation mechanism of hiss triggered chorus. Band limited VLF hiss emissions in the off-equatorial region of the magnetosphere can deform the electron distribution to give enhanced linear whistler instability near the upper cutoff frequency. Non-self-consistent computations of the nonlinear resonant particle currents produced by a large amplitude hiss band confirm a sharp peak in growth rate near the top of the band. At low amplitudes this peak would appear to be mainly due to the deformation of the phase averaged distribution function by multipass interaction with the hiss band. At higher root-mean-square amplitudes, of order of 50 pT, nonlinear wave-particle interaction effects seem to predominate. Enhanced growth rates at the top of the band will produce coherent narrow band wavelets which can trigger chorus elements through nonlinear wave-particle interaction effects }, keywords={ atmospherics magnetospheric electromagnetic wave propagation generation mechanism hiss triggered chorus VLF hiss emissions magnetosphere electron distribution enhanced linear whistler instability nonlinear resonant particle currents growth rate nonlinear wave-particle interaction effects }, mynotes={UNREAD}, }, @CONFERENCE{Nunn89, title={ Simulation of nonlinear wave particle interactions in space plasmas using the VHS technique }, booktitle={IEEE Conference Record - Abstracts. 1989 IEEE International Conference onPlasma Science (Cat. No.89CH2760-7)}, volume={}, number={}, year={1989}, month={}, pages={94-5}, abstract={ Summary form only. A technique for the numerical simulation of nonlinear wave particle interactions in a collision free space plasma is reported. The problem considered is the interaction between a continuous distribution of hot electrons and narrowband or quasi-narrowband electromagnetic radiation in the VLF band (4 kHz). These nonlinear wave-particle interactions cause a wide variety of phenomena in the VLF band, most notably triggered VLF emissions. In this study, a rising frequency emission has been simulated. An efficient technique termed Vlasov hybrid simulation (VHS) has been used. The key feature of this technique is described }, keywords={ electromagnetic wave propagation in plasma magnetosphere plasma simulation VLF band EM radiation magnetosphere nonlinear wave particle interactions space plasmas VHS technique numerical simulation hot electrons rising frequency emission Vlasov hybrid simulation 4 kHz }, mynotes={UNREAD}, }, @ARTICLE{OhmiDec86, author={Ohmi, N. and Hayakawa, M.}, title={ On the propagation of half-gyrofrequency whistler-mode waves in the magnetospheric plasma }, journal={Journal of Plasma Physics}, volume={36}, number={}, year={1986}, month={Dec}, pages={379-85}, abstract={ The propagation of whistler-mode waves at frequencies above one-half the electron gyrofrequency has been investigated for a magnetospheric two-component plasma (cold and lower energy hot electrons) by use of the properties of refractive index surfaces. The presence of hot plasma is found to enhance the tendency towards field-aligned focusing of half-gyrofrequency whistler-mode propagation at large wave normal angles close to the oblique resonance angle of the whistler-mode propagation in the corresponding cold plasma }, keywords={ magnetospheric electromagnetic wave propagation plasma whistlers cold electrons propagation half-gyrofrequency whistler-mode waves magnetospheric plasma two-component plasma hot electrons refractive index surfaces field-aligned focusing wave normal angles oblique resonance angle }, mynotes={UNREAD}, }, @ARTICLE{OhmiSep86, author={Ohmi, N. and Hayakawa, M. and Ohtsu, J.}, title={ On the polarization of half-gyrofrequency whistler-mode waves in the two-component magnetospheric plasma }, journal={Journal of the Physical Society of Japan}, volume={55}, number={9}, year={1986}, month={Sep}, pages={2915-18}, abstract={ Quasi-electrostatic half-gyrofrequency whistler-mode VLF emissions with wave normals close to the oblique resonance cone ( theta /sub res/) have been found to be unstable for the two-component (cold and anisotropic lower-energy hot electrons) magnetospheric plasma. The authors deal theoretically with the electric field polarization of half-gyrofrequency whistler-mode waves in such an unstable plasma, by numerically solving the full dispersion relation. At wave normal angles relatively far away from theta /sub res/, there exists no effect of hot electrons on the polarization. When the wave normal angle further increases above a specific value (smaller by 5-10 degrees from theta /sub res/) where there is wave growth, they expect a deformation of electric field polarization from that predicted by cold plasma theory; the wave becomes more transverse. The deformation becomes more pronounced for more populated hot electrons with fixed cold plasma density }, keywords={ electromagnetic wave propagation magnetosphere magnetospheric electromagnetic wave propagation whistlers hot electron effects EM wave propagation plasma instability transverse wave half-gyrofrequency whistler-mode waves two-component magnetospheric plasma VLF emissions anisotropic lower-energy hot electrons electric field polarization unstable plasma dispersion relation wave normal angles cold plasma density }, mynotes={UNREAD}, }, @ARTICLE{OhtaMar90, author={Ohta, K. and Hayakawa, M.}, title={ The correlation of whistler occurrence rate at a low latitude with thunderstorm activity at its conjugate region and with solar activity }, journal={Pure and Applied Geophysics}, volume={133}, number={1}, year={1990}, month={Mar}, pages={167-78}, abstract={ The correlations of the occurrence rate of whistlers in January during one solar cycle (1977-1987) at a low latitude station (Yamaoka, geomag. lat. 25 degrees , L=1.26) with thunderstorm activity near its conjugate region and also with solar activity have been investigated; and it is found that the occurrence rate has no correlation with the lightning flashes near the conjugate point, while it is negatively correlated with solar activity. On the basis of these findings it is suggested that the ionospheric absorption is of major importance in the long-term variation of whistler occurrence rate, with the duct formation being of secondary importance, while the lightning activity is only a necessary condition for whistler occurrence }, keywords={ electromagnetic wave absorption ionospheric electromagnetic wave propagation lightning meteorology solar-terrestrial relationships thunderstorms whistlers solar cycle 21 low-latitude whistlers N Australia AD 1977 to 1987 magnetosphere duct formation Japan solar-terrestrial relationships ionosphere EM wave propagation geomagnetic latitude 25 degrees N whistler occurrence rate thunderstorm activity conjugate region solar activity January low latitude station Yamaoka lightning flashes ionospheric absorption long-term variation lightning activity }, mynotes={UNREAD}, }, @ARTICLE{OhtaDec85, author={Ohta, K. and Okada, T.}, title={ Latitudinal variation of absolute intensities of daytime whistlers }, journal={Transactions of the Institute of Electronics and Communication Engineers ofJapan, Part B}, volume={J68B}, number={12}, year={1985}, month={Dec}, pages={1493-9}, abstract={ An accurate estimation of absolute intensity of whistlers is of great importance in studying the propagation characteristics of VLF waves in the ionosphere and magnetosphere. The measurement of whistler intensity is made possible after determining the incident wave normal direction and wave polarisation by means of direction finding. The authors report the electric field strength as estimated by their field-analysis direction finding systems at two different geomagnetic latitudes, Yamaoka (25 degrees N) and Moshiri (35 degrees N). The latitudinal dependence of the intensity is reasonably interpreted in terms of the latitudinal effect of the ionospheric absorption loss }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation radio direction-finding radiowave propagation whistlers ionospheric EM wave propagation absolute intensities daytime whistlers propagation characteristics VLF waves magnetosphere incident wave normal direction wave polarisation direction finding electric field strength field-analysis direction finding systems geomagnetic latitudes Yamaoka 25 degrees N Moshiri 35 degrees N latitudinal dependence ionospheric absorption loss }, mynotes={UNREAD}, }, @CONFERENCE{Ohta89, author={Ohta, K. and Hayakawa, M. and Eguchi, H.}, title={ The frequency variation of the intensity of low-latitude whistler waves }, booktitle={ISAP Japan 1989. Proceedings of the 1989 International Symposium onAntennas and Propagation}, volume={}, number={}, year={1989}, month={}, pages={1077-80 vol.4}, abstract={ With a new spectrum analyzer using PCM recorders and an FFT analyzer, the authors investigate the fine structures of whistler spectra, especially the intensity change with frequency. As an interpretation of the patched whistlers observed at Yamaoka (geomag. lat. 25 degrees N), the transmission coefficients of whistler waves propagated downward through the irregular F region are calculated and compared with experiments }, keywords={ atmospheric spectra F-region ionospheric electromagnetic wave propagation whistlers Japan low-latitude whistler waves fine structures intensity frequency patched whistlers Yamaoka transmission coefficients irregular F region }, mynotes={UNREAD}, }, @ARTICLE{OhtaMay91, author={Ohta, K. and Hayakawa, M. and Shimakura, S. and Tomomatsu, T.}, title={ Correlation of whistlers at a low latitude with causative lightnings at conjugate regions }, journal={Transactions of the Institute of Electronics, Information and CommunicationEngineers B-II}, volume={J74B-II}, number={5}, year={1991}, month={May}, pages={276-84}, abstract={ The correlation of occurrence rate of whistlers in January during one solar cycle (1977-87) at low latitude Yamaoka (geomag. lat. 25 degrees N) with thunderstorm activity near its conjugate region and also with solar activity have been investigated. It is found that the occurrence rate has no correlation with the lightning flashes near the conjugate point, while it is negatively correlated with solar activity. On the basis of these findings it is suggested that the ionospheric absorption is of major importance in the long-term variation of whistler occurrence rate at low latitude, and the duct formation is of secondary effect, while the lightning activity is the only necessary condition for whistler occurrence }, keywords={ ionospheric electromagnetic wave propagation lightning magnetospheric electromagnetic wave propagation whistlers whistler occurrence rate VLF low latitude lightnings conjugate regions January 1977-87 Yamaoka thunderstorm activity solar activity ionospheric absorption }, mynotes={UNREAD}, }, @ARTICLE{OhtaNov96, author={Ohta, K. and Kitagawa, T. and Shima, N. and Hayakawa, M. and Dowden, R.L.}, title={ Characteristics of mid-latitude whistler ducts as deduced from ground-based measurements }, journal={Geophysical Research Letters}, volume={23}, number={23}, year={1996}, month={Nov}, pages={3301-4}, abstract={ Propagation characteristics of mid-latitude whistlers, especially whistler duct characteristics, have been investigated based on measurements in August, 1994 at Dunedin, New Zealand (L=2.78) and in August, 1989 at Ceduna, Australia (L=1.93), both during local midnight. Polarization analyses have enabled us to locate whistlers which exited the ionosphere just above the observing station (L/sub DF/ is defined in this way). The nose extension method was also applied to these whistlers (their L/sub n/ is estimated by this method). The following findings have emerged from the analyses; L/sub DF/ approximately=L/sub n/ (at Dunedin) and L/sub DF/ approximately=L/sub n/-0.43 (at Ceduna). Our analysis suggests that mid-latitude ducts are likely to extend down to the ionosphere at L approximately=2.8. Ray tracing studies for realistic density profiles indicates that a whistler duct terminates at an altitude of about 3500À5500 km at an L value of À1.9 with its enhancement factor being a few percent at least. These results may imply a strong variability of the latitudinal or temporal variations of mid-latitude whistler ducts }, keywords={ magnetospheric electromagnetic wave propagation radiowave propagation whistlers mid-latitude whistler ducts propagation characteristics polarization ionosphere nose extension method ray tracing density profiles enhancement factor 3500 to 5500 km }, mynotes={UNREAD}, }, @ARTICLE{OkadaJan80, author={Okada, T. and Iwai, A.}, title={ A new device for measurement of polarization and field intensity of low-latitude whistlers }, journal={Transactions of the Institute of Electrical Engineers of Japan}, volume={100}, number={1}, year={1980}, month={Jan}, pages={21-8}, abstract={ The design of a ground-based radio receiver system for the measurement of the polarisation and intensity of whistlers is described. The antenna and electronics required for analysing the signal are described. This apparatus was used to make observations of whistlers for December 1977 until February 1978 }, keywords={ atmospheric techniques ionospheric measuring apparatus ionospheric techniques magnetosphere whistlers EM wave polarisation VLF radiowave magnetosphere ionosphere apparatus radio receiver ground antenna electronics measurement field intensity low-latitude whistlers ground-based }, mynotes={UNREAD}, }, @ARTICLE{OkadaMar77, author={Okada, T. and Iwai, A. and Hayakawa, M.}, title={ The measurement of incident and azimuthal angles and the polarization of whistlers at low latitudes }, journal={Planetary and Space Science}, volume={25}, number={3}, year={1977}, month={Mar}, pages={233-41}, abstract={ In order to estimate the path latitude of low-latitude whistlers, the measurement of the direction of arrival (bearing and elevation) and the polarization has been successfully carried out by a low-latitude station at Takayama (geomag. lat. 26 degrees ), by using newly developed electronic devices. The system of using two crossed loops and a vertical monopole is, in principle, based on Crary's (1961) method and is effective for elliptically polarized waves. The measurements were made at a specific frequency of 4.5 kHz. The main results of the preliminary experiments are (i) the exit points of observed whistlers are located several tens of kilometers approximately north-north-east of the observing site and (ii) although a few whistlers have shown the polarization very close to circular, the polarization of most whistlers is generally elliptical, indicating the effect of multi-rays propagating in the Earth-ionosphere waveguide }, keywords={ atmospheric measuring apparatus ionospheric electromagnetic wave propagation polarisation whistlers azimuthal angles polarization whistlers low latitudes path latitude Takayama 4.5 kHz incident angles multiray propagation arrival direction VLF Earth ionosphere waveguide }, mynotes={UNREAD}, }, @ARTICLE{OlsenFeb92, title={ The density minimum at the Earth's magnetic equator }, journal={J. Geophys. Res. (USA), Journal of Geophysical Research}, volume={97}, number={A2}, year={1992}, month={Feb}, pages={1135-50}, abstract={ Observations of the density structure in the plasmapause region reveal the existence of a local minimum in the total electron density at the magnetic equator. Data from the plasma wave instrument and ion mass spectrometer on the Dynamics Explorer 1 satellite are used to study this phenomenon. The density depletion typically extends from +or-5 degrees to +or-20 degrees in latitude and is found at altitudes ranging from 2 to 5 R/sub E/. This density structure is associated with equator crossings where the thermal plasma has been heated over normal plasmasphere values }, keywords={ magnetosphere plasma magnetosphere plasma density structure plasmapause region local minimum total electron density magnetic equator Dynamics Explorer 1 satellite plasmasphere 2 to 5 Earthradii }, mynotes={UNREAD}, }, @ARTICLE{OlsonFeb85, author={Olson, J.V. and Domke, R.}, title={ Instrument to measure the polarization of waves }, journal={Review of Scientific Instruments}, volume={56}, number={2}, year={1985}, month={Feb}, pages={278-82}, abstract={ The authors report on the design and implementation of analog circuitry which allows the processing of the components of vector waveforms to obtain polarization information. The waveforms are the voltages derived from orthogonal sensors such as magnetometers or seismometers which provide information on the time variation of vector processes. The circuits take the voltages from the individual sensors and process them to produce estimates of the spectral matrix at a particular frequency. From the components of the spectral matrix one may determine the wave polarization parameters including the signal power, ellipticity, handedness, and orientation of the polarization ellipse. In cases where the information of interest to the investigator depends upon the relatively slow modulations of a carrier and not upon the frequency of the carrier itself, the preprocessing of the spectral information is described allows the investigator to sample the data at a much reduced rate, or with a narrower bandwidth, without loss of information. The authors have implemented the circuits described in their investigation of electromagnetic waves in the ULF (3 mHz-3 Hz) frequency band and have achieved a reduced demand for storage and processing capacities in the project }, keywords={ electromagnetic wave polarisation magnetometers polarisation seismic waves seismometers signal processing equipment waveform analysis signal processing equipment waveform analysis EM waves polarization of waves vector waveforms orthogonal sensors magnetometers seismometers time variation of vector processes spectral matrix signal power ellipticity handedness orientation electromagnetic waves ULF }, mynotes={UNREAD}, }, @ARTICLE{OlsonNov70, title={ A magnetospheric cyclotron }, journal={Transactions of the American Geophysical Union}, volume={51}, number={11}, year={1970}, month={Nov}, pages={812}, abstract={ Due to the varying angle between the (constant) solar wind direction and the geomagnetic dipole axis the strength of the magnetopause magnetic field is continuous changing even when solar wind parameters are constant in time. Therefore, in any reference frame the total geomagnetic field, B, is changing with time and has an induction electric field E associated with it. E has a large component whose direction varies approximately sinusoidally with a period of one day and is perpendicular to B. Charge particles drifting in the magnetosphere will be influenced by both B and E. As the particles accelerate they move to a region of larger B, i.e., toward the earth. Preliminary estimates of E suggest its strength is 0.1-0.3. volts/km. In the outer magnetosphere this mechanism can act to accelerate a solar wind particle from 1 keV to tens of keV in several hours. The action of this 'magnetospheric cyclotron' is continuous and is competitive with random processes that have been suggested as sources of radial diffusion }, keywords={ geomagnetic variations magnetosphere upper atmosphere magnetospheric cyclotron particle acceleration solar wind particles geomagnetic field variations induction electric field }, mynotes={UNREAD}, }, @CONFERENCE{Omid94, author={Omid, M. and hayakawa, M.}, title={ Excitation of EM waves by current source sheets in the Earth's ionosphere }, booktitle={1994 International Symposium on Electromagnetic Compatibility (IEEE Cat.No.94TH0680-9)}, volume={}, number={}, year={1994}, month={}, pages={701-4}, abstract={ Excitation of the Earth's ionosphere by transient sources is considered, for a general multicomponent collisional magnetoplasma. The temporal and spatial evolution of wave packets is analyzed for typical plasma parameters pertaining to the day time F/sub 2/-layer plasma, by an exact numerical inversion method of the Laplace transform. The properties of these excited waves as a function of theta , where theta is the angle that the Earth's magnetic field makes with the wave normal, are discussed in different frequency bands; (i) quasi-free space modes, (ii) whistler mode and (iii) hydromagnetic wave modes. The obtained results provide explicit information about the nature of the transient response and may have applications to diagnostic techniques in magnetoplasmas by relating cold plasma theory to specific features in the wave packet }, keywords={ electromagnetic wave propagation F-region ionosphere Laplace transforms magnetohydrodynamic waves radiowave propagation whistlers EM waves excitation current source sheets Earth ionosphere transient sources multicomponent collisional magnetoplasma spatial evolution temporal evolution plasma parameters daytime F/sub 2/ layer plasma exact numerical inversion method Laplace transform geomagnetic field frequency bands quasifree space modes whistler mode hydromagnetic wave modes transient response diagnostic techniques cold plasma theory transient propagation }, mynotes={UNREAD}, }, @CONFERENCE{Omura85, author={Omura, Y. and Matsumoto, H.}, title={ Nonlinear amplification of whistler mode waves in an inhomogeneous magnetic field }, booktitle={ISAP Japan 1985. Proceedings of the 1985 International Symposium onAntennas and Propagation, Japan - A Step to New Radio Frontiers}, volume={}, number={}, year={1985}, month={}, pages={995-8 vol.3}, abstract={ Nonlinear amplification of a monochromatic VLF whistler mode wave propagating along the geomagnetic field is studied via computer simulations. Natural and controlled whistler-mode signals have been used at simple stateion. Antartica (and its conjugate, Roberval, Quebec to study the nonlinear mechanism of wave growth in the magtnetosphere. However, the detailed nonlinear features involved in the interactions. The basic processes of the wave growth are investigated with the aid of self-consistent computer simulations. The simulation method used in the present study ise Long-Time-Scale (LTS) code (Rathmann et al., 1978, Matsumoro and Omura, 1985) where cold plasma is treated as a fluid and hot plasma is treated as particles }, keywords={ magnetospheric electromagnetic wave propagation radiowave propagation whistlers nonlinear amplification radiowave propagation whistler mode waves inhomogeneous magnetic field monochromatic VLF whistler mode wave geomagnetic field computer simulations nonlinear mechanism wave growth magtnetosphere }, mynotes={UNREAD}, }, @ARTICLE{OndohMay96, author={Ondoh, T. and Nakamura, Y.}, title={ Characteristics of VLF emissions observed by DE-1 in the equatorial magnetosphere }, journal={Adv. Space Res. (UK), Advances in Space Research}, volume={17}, number={10}, year={1996}, month={May}, pages={99-104}, abstract={ Whistler-triggered hiss, banded hiss, ELF hiss, impulsive VLF waves and magnetospheric chorus are analysed by using analog data of wideband electric fields (650 Hz-40 kHz) from the DE-1 satellite received at Kashima, Japan in the NASA DE guest investigator program. The whistler-triggered hiss was observed after a whistler trace at frequencies below about 15 kHz in low-latitude plasmasphere, and its generation models are discussed. Wave modes of banded hiss, impulsive VLF waves and ELF hiss successively observed for about one minute are discussed in terms of the spin modulated effect of whistler-mode ELF hiss. Magnetospheric chorus with a frequency gap around 5.8 kHz was observed in the geomagnetic storm recovery phase. This indicates a field decrease by about one fifth of the quiet-time geomagnetic field produced by a storm-time equatorial ring current }, keywords={ magnetic storms magnetospheric electromagnetic wave propagation plasma electrostatic waves radiowave propagation whistlers VLF emissions equatorial magnetosphere whistler triggered hiss banded hiss ELF hiss impulsive VLF waves magnetospheric chorus electric fields DE 1 satellite data low latitude plasmasphere generation models spin modulated effect geomagnetic storm ring current 650 Hz to 40 kHz 15 kHz 5.8 kHz }, mynotes={UNREAD}, }, @ARTICLE{OndohMar86, author={Ondoh, T. and Nakamura, Y. and Watanabe, S.}, title={ Solar-terrestrial disturbances of June-September 1982. IV. Ionospheric disturbances. VI. Magnetospheric VLF emissions observed by ISIS satellites during four geometric storms in July and September 1982 }, journal={Journal of the Radio Research Laboratories}, volume={33}, number={}, year={1986}, month={Mar}, pages={165-80}, abstract={ Wide-band VLF hiss similar to auroral hiss, chorus and a hook-type emission were observed at mid-latitudes during the daytime for four geomagnetic storms in July and September 1982 by ISIS satellites at Kashima Station, Radio Research Laboratories (RRL), Japan. The auroral type hiss observed at mid-latitudes seems to be generated by the Cherenkov radiation from precipitating electrons with energy above a few keV. The precipitating electrons may result from an interaction of the ring current particles with the plasmaspheric cold plasma. The occurrence of chorus at mid-latitudes during the geomagnetic storm of September 22 seems to represent inward movements of the outer-radiation-zone electrons due to an enhanced westward electric field in the magnetosphere during the geomagnetic storm. Another storm effect observed is that the upper limit frequency, lower limit frequency and bandwidth of ELF hiss became smaller at lower latitudes }, keywords={ atmospheric electron precipitation atmospheric radiation magnetic storms magnetosphere radiation belts radiation belt AD 1982 07 to 09 atmospheric ionosphere VLF emissions geometric storms auroral hiss chorus hook-type emission mid-latitudes Japan Cherenkov radiation precipitating electrons ring current particles plasmaspheric cold plasma outer-radiation-zone electrons electric field magnetosphere frequency bandwidth ELF }, mynotes={UNREAD}, }, @ARTICLE{OndohApr89, author={Ondoh, T. and Nakamura, Y. and Watanabe, S. and Aikyo, K.}, title={ Impulsive plasma waves observed by DE 1 in nightside magnetosphere }, journal={Journal of Geophysical Research}, volume={94}, number={A4}, year={1989}, month={Apr}, pages={3779-84}, abstract={ Impulsive plasma waves with a frequency range of 1-9 kHz were found in the wide-band electric field data from the DE 1 satellite received at the Kashima station in Japan. The impulsive plasma waves were often accompanied by a strong hiss band at about 1 kHz, but not by a chorus. The frequency-time spectra of these waves are very similar to those of electrostatic bursts associated with ELF chorus in the outer dayside magnetosphere, but these impulsive waves were observed at low geomagnetic latitudes in nightside magnetospheric regions much nearer the Earth for geomagnetic quiet and disturbed times. It is inferred from the local plasma density and the empirical relation of the plasmapause position with Kp that the impulsive plasma waves are occurring just outside the plasmapause. The impulsive plasma waves are discussed in terms of a resistive medium instability caused by Landau resonant trapping of thermal electrons by the associated hiss band at about 1 kHz }, keywords={ magnetosphere radiowave emission impulsive plasma wave AD 1986 07 30 plasma instability nightside magnetosphere strong hiss band plasmapause position resistive medium instability Landau resonant trapping thermal electrons 1 to 9 kHz }, mynotes={UNREAD}, }, @ARTICLE{OndohJul93, title={ Narrow-band plasmapause hiss observed by ISIS satellites }, journal={Radio Science}, volume={28}, number={4}, year={1993}, month={Jul}, pages={629-42}, abstract={ Typical frequency-time spectra of narrow-band hiss obtained near plasmapause latitude from ISIS VLF electric field data (50 Hz to 30 kHz) telemetered at Syowa Station, Antarctica, under quiet conditions, are similar to those of narrow-band 5-kHz hiss observed at mid-latitudes and low latitudes on the ground. This hiss in the topside ionosphere first appeared as a thin, bar-shaped emission around 5 kHz at geomagnetic invariant latitude of about 56 degrees and grew into a wider band between 3 and 6 kHz at invariant latitudes around 60 degrees which is the average plasmapause latitude. Then, at higher latitudes, the band narrowed somewhat and disappeared around 65 degrees . The hiss had no lower-frequency cutoff, and its center frequency remained approximately constant at 5 kHz, between about 56 degrees and 65 degrees . This narrow-band hiss is completely different from the electrostatic LHR hiss which is also observed above the ionosphere with an electric antenna, but which has latitude-dependent lower-frequency cutoff. Since the narrow-band 5-kHz hiss occurs often around plasmapause latitude (60 degrees ), hereafter we will call this hiss narrow-band plasmapause hiss. Latitude and local time distributions of the occurrence rate for narrow-band plasmapause hiss were obtained by analyzing six-frequency narrow-band data processed from the wideband VLF signals received at Syowa Station from ISIS 1 and ISIS 2 during 507 passes between December 1976 and January 1983. Although when taken over the whole latitude range, 55 degrees to 64 degrees , the occurrence rate of narrow-band plasmapause hiss under various geomagnetic conditions (Kp = 0-6) is 0.83, the rate at any given latitude is below 0.35. Thus it is rather a rare phenomenon as compared with LHR hiss. The peak occurrence rate lies at 58 degrees to 59 degrees , under geomagnetically quiet and moderate conditions (Kp = 0-3) and extends over the somewhat broader range of 56 degrees to 60 degrees under disturbed conditio }, keywords={ atmospheric radiation atmospherics magnetosphere whistlers narrowband plasmapause hiss ISIS satellites frequency-time spectra VLF electric field data Antarctica topside ionosphere geomagnetic invariant latitude plasmapause latitude local time distributions geomagnetic conditions occurrence rate magnetic local time distribution magnetosphere whistler mode cyclotron resonant instability energetic electrons Syowa Station 50 Hz to 30 kHz }, mynotes={UNREAD}, }, @ARTICLE{OndohMay90, title={ Broad-band auroral VLF hiss and inverted-V electron precipitation in the polar magnetosphere }, journal={J. Atmos. Terr. Phys. (UK), Journal of Atmospheric and Terrestrial Physics}, volume={52}, number={5}, year={1990}, month={May}, pages={385-97}, abstract={ A polar map of the occurrence rate of broad-band auroral VLF hiss in the topside ionosphere was made using narrow-band intensity data processed from VLF electric field (50 Hz-30 kHz) tapes of 347 ISIS passes received at Syowa Station, Antarctica between June 1976 and January 1983. The low-latitude contour of occurrence rate of 0.3 is approximately symmetric with respect to the 10-22 MLT (geomagnetic local time) meridian. It lies at 74 degrees around 10 MLT, and extends down to 67 degrees around 22 MLT. The high-latitude contour of 0.3 lies at invariant latitude of about 82 degrees for all geomagnetic local times. The frequency range of the downgoing broad-band auroral hiss seems to be explained by the whistler mode Cerenkov radiation generated from inverted-V electrons at geocentric distances below about 2 R/sub E/ along polar geomagnetic field lines of invariant latitude from 70 to 77 degrees }, keywords={ atmospheric electron precipitation atmospheric radiation atmospherics aurora Cherenkov radiation ionosphere magnetosphere whistlers VLF hiss occurrence rate VLF hiss frequency range invariant latitude 82 degrees S invariant latitude 70 degrees to 77 degrees AD 1976 06 to 1983 01 ELF aeronomy Cherenkov radiation upper frequency limit inverted-V electron precipitation polar magnetosphere polar map broad-band auroral VLF hiss topside ionosphere narrow-band intensity data ISIS passes Syowa Station Antarctica June 1976 January 1983 low-latitude contour high-latitude contour geomagnetic local times downgoing broad-band auroral hiss whistler mode Cerenkov radiation geocentric distances polar geomagnetic field lines 1 to 30 keV 0.3 to 20 kHz 3.2 Mm 6.4 Mm 1 to 2 Earthradii }, mynotes={UNREAD}, }, @ARTICLE{OndohMar90, title={ Broad-band auroral hiss and inverted-V electrons precipitated from the boundary plasma sheet }, journal={Journal of the Communications Research Laboratory}, volume={37}, number={150}, year={1990}, month={Mar}, pages={15-28}, abstract={ A polar map of the occurrence rates for broad-band auroral hiss, obtained from ISIS VLF data, is compared to one for the occurrence locations of inverted-V electron precipitations, obtained from Atmospheric Explorer (AE)-D. The occurrence map for broad-band auroral hiss is qualitatively similar to that for the inverted-V electron precipitations; especially, concerning the low-latitude boundary and axial symmetry of the 10-22 hour geomagnetic local time (MLT) meridian. The frequency range of the hiss is discussed in terms of whistler-mode Cherenkov radiation by inverted-V electrons precipitated from the boundary plasma sheet. The frequencies of this radiation are higher when generated at lower altitudes than when generated at higher altitudes on the same field line, since whistler-mode Cherenkov radiation has an upper limit frequency }, keywords={ atmospheric electron precipitation atmospheric radiation ionosphere magnetosphere radiofrequency interference VLF radio noise ISIS satellites magnetosphere ionosphere boundary plasma sheet polar map occurrence rates broad-band auroral hiss ISIS VLF data inverted-V electron precipitations low-latitude boundary axial symmetry geomagnetic local time frequency range whistler-mode Cherenkov radiation boundary plasma sheet altitudes 12 kHz 40 keV 3200 km 6400 km 2 kHz }, mynotes={UNREAD}, }, @ARTICLE{OnsagerSep93, author={Onsager, T.G. and Thomsen, M.F. and Elphic, R.C. and Gosling, J.T. and Anderson, R.R. and Kettmann, G.}, title={ Electron generation of electrostatic waves in the plasma sheet boundary layer }, journal={Journal of Geophysical Research}, volume={98}, number={A9}, year={1993}, month={Sep}, pages={15509-19}, abstract={ Broadband electrostatic noise (BEN) is a common feature of the plasma sheet boundary layer in the Earth's magnetotail. Observationally, BEN has been shown to occur in conjunction with ion beams. The authors present simultaneous observations of ion and electron distribution functions and electric field wave spectra measured by ISEE 1 and ISEE 2 in the Earth's magnetotail. They have used particularly slow traversals of the boundary layer where the distinct electron and ion boundaries can be clearly resolved. As the spacecraft moved from the tail lobe toward the plasma sheet, the first indication of boundary layer plasma was seen in the electron distributions, followed some minutes later by the detection of boundary layer ions. The onset of large-amplitude electrostatic waves at frequencies up to the electron plasma frequency was coincident with the onset of the boundary layer electrons. This evidence suggests that broadband electrostatic waves may often be generated by unstable electron distributions in the plasma sheet boundary layer, particularly the high-frequency portion of the wave spectrum. The lower-frequency waves are found to be polarised perpendicular to the background magnetic field, consistent with previous observations. The higher-frequency waves (near the electron plasma frequency) had perpendicular polarization when the amplitudes were low and parallel polarisation when the amplitudes were high }, keywords={ magnetosphere plasma plasma waves electrostatic waves plasma sheet boundary layer electron generation broadband electrostatic noise magnetotail electron distribution function ion distribution function electric field wave spectra ISEE 1 ISEE 2 unstable electron distributions polarisation magnetosphere }, mynotes={UNREAD}, }, @ARTICLE{Orlowski95, author={Orlowski, D.S. and Russell, C.T. and Krauss-Varban, D. and Omidi, N. and Thomsen, M.F.}, title={ Propagation and damping of broadband upstream whistlers }, journal={Adv. Space Res. (UK), Advances in Space Research}, volume={15}, number={8-9}, year={1995}, month={}, pages={85-92}, abstract={ Previous studies indicated that damping rates of upstream whistlers strongly depend on the details of the electron distribution function. Moreover, detailed analysis of Doppler-shift and whistler dispersion relation indicated that upstream whistlers propagate obliquely in a broad band. In this paper we present results of a kinetic calculation of damping lengths of wide-band whistlers using the sum of 7-drifting bi-Maxwellian electron distributions as a best fit to the ISEE 1 electron data. For two cases, when upstream whistlers are observed, convective damping lengths derived from ISEE magnetic field and ephemeris data are compared with theoretical results. We find that the calculated convective damping lengths are consistent with the data and that upstream whistlers remain marginally stable. We also show that the slope of plasma frame spectra of upstream whistlers, obtained by direct fitting of the observed spectra is between 5 and 7 with a sharp lower frequency cutoff corresponding to a wavelength of about one ion inertial length. When the solar wind velocity is directed largely along the wave normal of the upstream whistlers the polarization of the right hand waves becomes reversed and low frequencies are switched to high resulting in a peaked spectrum with a strong high frequency cutoff. The overall spectral, wave and particle characteristics, proximity to the shock as well as propagation and damping properties indicate that these waves cannot be generated locally. Instead the observed upstream whistlers arise in the shock ramp most likely by a variety of cross-field drift and/or anisotropy driven instabilities }, keywords={ magnetospheric electromagnetic wave propagation plasma shock waves whistlers broadband whistlers damping rates propagation kinetic calculations electron distribution function analytical model plasma frame spectra ISEE data shock waves upstream whistlers convective damping length }, mynotes={UNREAD}, }, @ARTICLE{OtaOct87, author={Ota, K. and Mao Tian, Cunchen Tang and Baba, K. and Eguchi, H.}, title={ The frequency dependence of the exit points of whistler }, journal={Memoirs of College of Engineering, Chubu University}, volume={23}, number={}, year={1987}, month={Oct}, pages={45-51}, abstract={ The authors have developed a field-analysis direction finding method, based on the simultaneous measurement of two horizontal magnetic components, and one vertical field component. The measurement is made at a specific point frequency around 5 kHz where the maximum energy is expected in the whistler spectrum. It is of great interest whether the results of direction of arrival and polarization, measured at the particular frequency, can be generalized to a wide frequency band. The extension of the direction finding system to a wide frequency band, using the PCM recorder and FFT analyzer, is studied }, keywords={ magnetospheric electromagnetic wave propagation whistlers whistler arrival direction whistler polarisation magnetosphere EM wave propagation frequency dependence exit points whistler field-analysis direction finding method simultaneous measurement horizontal magnetic components vertical field component specific point frequency maximum energy whistler spectrum wide frequency band 5 kHz }, mynotes={UNREAD}, }, @ARTICLE{ParrotFeb90, title={ World map of ELF/VLF emissions as observed by a low-orbiting satellite }, journal={Annales Geophysicae. Atmospheres, Hydrospheres and Space Sciences}, volume={8}, number={2}, year={1990}, month={Feb}, pages={135-46}, abstract={ Statistical studies were performed of the intensities of the ELF/VLF emissions observed by the low-orbiting satellite Aureol-3. Data were obtained from filterbanks and the frequency range of observations extends from a few tens of Hz up to 15 kHz. The most important phenomena observed are ELF hiss and VLF hiss. Electric and magnetic components are used. The data were continuously registered with on-board tape recorders and then transmitted to a reception station. Thus, representation of the wave intensities in geographical coordinates was made at different frequencies. The relative ability of natural waves (whistler, hiss) and man-made waves, such as powerful VLF transmitters or powerline harmonic radiations, to precipitate particles in the slot region, is studied }, keywords={ atmospheric radiation atmospherics magnetosphere particle precipitation magnetosphere global map ELF/VLF emissions low-orbiting satellite Aureol-3 hiss wave intensities whistler powerline harmonic radiations slot region 10 Hz to 16 kHz }, mynotes={UNREAD}, }, @ARTICLE{PaschalJan90, title={ Whistler precursors on a VLF transmitter signal }, journal={Journal of Geophysical Research}, volume={95}, number={A1}, year={1990}, month={Jan}, pages={225-31}, abstract={ Whistler precursors are discrete emissions which are occasionally seen just before two-hop whistlers. Most theories of precursors assume that they are triggered emissions and focus on creating a triggering signal with the proper time delay from the causative sferic. Whistler precursors have been seen on a signal from the Siple VLF transmitter. Phase analysis shows that these precursors are caused by a rapid increase in growth activity, and not by a triggering signal }, keywords={ atmospheric radiation atmospherics magnetospheric electromagnetic wave propagation plasma whistlers whistler precursors Roberval Quebec Antarctica wave-particle growth activity increase ELF AD 1983 02 09 AD 1983 09 02 magnetosphere EM wave propagation discrete emissions two-hop whistlers 1 to 5 kHz 3.9 to 4.1 kHz }, mynotes={UNREAD}, }, @ARTICLE{PerezNov70, author={Perez, J.K. and Northrop, T.G.}, title={ Stationary waves produced by the Earth's bow shock }, journal={Journal of Geophysical Research}, volume={75}, number={31}, year={1970}, month={Nov}, pages={6011-23}, abstract={ Cyclotron waves should be produced upstream and downstream from the bow shock by current in the shock. Amplitudes and polarizations of waves produced by a steady thin current sheet in the plane of the shock have been calculated by using cold plasma dispersion relations. The steady current leads to waves that are stationary in the shock frame. Waves upstream from the shock are circularly polarized electron waves, the polarization is in the sense of a right-hand screw when the interplanetary field is directed generally toward the shock and of a left-hand screw when the field is directed away. The downstream magnetic wave field has two components, one from the electron cyclotron branch and one from the ion cyclotron branch of the dispersion relation. The second component has a longer wavelength and a larger amplitude (by the ion/electron mass ratio) than the electron wave. It is elliptically rather than circularly polarized and is always polarized in the opposite sense to the upstream electron wave }, keywords={ magnetosphere }, mynotes={UNREAD}, }, @ARTICLE{PintoSep89, author={Pinto, O. and Jr. and Gonzalez, W.D.}, title={ The role of Landau resonance in energetic electron precipitation from the inner radiation belt }, journal={Journal of Geophysical Research}, volume={94}, number={A9}, year={1989}, month={Sep}, pages={12027-30}, abstract={ The role of Landau resonance between energetic electrons and plasmaspheric hiss waves at the inner radiation belt is investigated. These nearly structureless turbulent waves have been observed to exist at the inner belt over a large range of latitudes and to propagate with a wide distribution of wave normal angles relative to the geomagnetic field. For these waves, the authors show that at low L values, Landau resonance with electrons near their mirror points can give pitch angle diffusion coefficients larger than those expected for equivalent cyclotron resonances at the equator. The authors suggest that this resonance may be regarded as the most important process to explain the enhancement in energetic electron precipitation at the inner belt, at least during the recovery phase of storms }, keywords={ atmospheric electron precipitation magnetospheric electromagnetic wave propagation plasma radiation belts radiowave propagation magnetic storm magnetosphere atmosphere plasma Landau resonance energetic electron precipitation inner radiation belt energetic electrons plasmaspheric hiss waves structureless turbulent waves mirror points pitch angle diffusion coefficients recovery phase }, mynotes={UNREAD}, }, @ARTICLE{PotteletteMay90, author={Pottelette, R. and Malingre, M. and Dubouloz, N. and Aparicio, B. and Lundin, R. and Holmgren, G. and Marklund, G.}, title={ High-frequency waves in the cusp/cleft regions }, journal={Journal of Geophysical Research}, volume={95}, number={A5}, year={1990}, month={May}, pages={5957-71}, abstract={ Because of the high time resolution of many of its scientific instruments, the Viking satellite has detected the presence of intense wave bursts in the cusp/cleft regions, at altitudes between 1 and 2 Earth radii. These bursts are closely related to the acceleration processes of charged particles and are characterized by a strong plasma turbulence illustrated by sporadic and intense broadband electrostatic noise detected in the 4- to 700-kHz frequency range of the high-frequency wave receiver. The duration of such bursts is small, typically a few hundreds of milliseconds, corresponding to a spatial width less than 1 km at the satellite altitude. The low-frequency part of this noise is always the most intense, with electric field amplitudes of a few tens of millivolts per meter. This noise is correlated with 0.1-1-keV electron beams and with small-scale field-aligned currents and is always associated with low-frequency ( approximately 1 Hz) electric field fluctuations. Perpendicular acceleration of ambient plasma ions occurs in connection with the bursts. The impulsive broadband waves are detected at the equatorward edge of the polar cusp and more generally in the entire cleft region }, keywords={ magnetosphere high-frequency wave magnetosphere cusp cleft region plasma wave radiowave emission AD 1986 07 intense wave bursts intense broadband electrostatic noise electron beams }, mynotes={UNREAD}, }, @ARTICLE{PrakashDec94, author={Prakash, R. and Singh, R.P.}, title={ Wide-band whistler-mode limiting magnetic field intensity and measurement of strength of pitch angle diffusion of resonant electrons }, journal={Indian Journal of Radio & Space Physics}, volume={23}, number={6}, year={1994}, month={Dec}, pages={403-9}, abstract={ Following linear theory and adopting the well known Fokker Planck expression for the diffusion coefficient, expressions for the limiting magnetic field intensity of wide-band whistler-mode waves and the diffusion parameter have been derived. The diffusion parameter is shown to be equal to the ratio of the experimentally observed intensity to the limiting intensity. In order to measure diffusion strength, the theoretically calculated limiting magnetic field intensities are then compared with the magnetic field intensities observed experimentally both inside and outside the plasmasphere. The results show that strong diffusion is impossible at L-40R/sub E/) as an ellipsoid of revolution in solar-wind-aberrated coordinates and express the (p,B/sub z/) dependence of each of the three ellipsoid parameters as a second-order (6-term) bivariate expansion in lnp and B/sub z/. They define 12 overlapping bins in a normalized dimensionless (p,B/sub z/) 'control space' and fit an ellipsoid to those magnetopause crossings having (p,B/sub z/) values within each bin. They also calculate the bivariate (lnp,B/sub z/) moments to second order over each bin in control space. They can then calculate the six control-space expansion coefficients for each of the three ellipsoid parameters in configuration space. From these coefficients they can derive useful diagnostics of the magnetopause shape as joint functions of p and B/sub z/: the aspect ratio of the ellipsoid's minor-to-major axes; the flank distance, radius of curvature, and flaring angle (at X/sub GSE/=0); and the subsolar distance and radius of curvature }, keywords={ interplanetary magnetic fields magnetosphere solar wind magnetopause shape morphology IMF B/sub z/ solar wind magnetosphere interaction bivariate function interplanetary magnetic field solar wind dynamic pressure ellipsoid of revolution solar-wind-aberrated coordinates }, mynotes={UNREAD}, }, @ARTICLE{Roussel-DupreApr93, author={Roussel-Dupre, R. and Miller, R.H.}, title={ Radiative properties of a plasma moving across a magnetic field. II. Numerical results }, journal={Physics of Fluids B (Plasma Physics)}, volume={5}, number={4}, year={1993}, month={Apr}, pages={1306-31}, abstract={ For pt.I see ibid., vol.5, no.4, p.1306-31 (1993). A theoretical analysis developed in a companion paper to treat the early-time evolution of plasmas moving across a background magnetic field is applied to the modeling of low-beta, barium chemical releases in the magnetosphere. The results indicate that radiation damping plays an important role in defining the plasma cloud evolution, causing a rapid decay of the polarization field and a loss of plasma kinetic energy and momentum on time scales comparable to several ion gyroperiods. The radiation spectrum consists of a burst of chirped, high-frequency (in the range of the cloud plasma frequencies) waves, followed by a pulse of whistler waves, and subsequently by ion cyclotron emission. Scaling laws are derived for the plasma momentum and energy loss rates and predictions for the braking time, the amplitude and spectrum of the radiation field, and the total radiated power are presented for conditions relevant to the recent Combined Release and Radiation Effects Satellite (CRRES) experiments (Phys. Fluids B4, 2249 (1992)) }, keywords={ magnetosphere plasma plasma magnetohydrodynamics plasma waves whistlers radiative properties chirped HF waves scaling laws early-time evolution chemical releases magnetosphere radiation damping plasma cloud evolution polarization field plasma kinetic energy time scales ion gyroperiods whistler waves ion cyclotron emission plasma momentum energy loss rates braking time total radiated power Ba }, mynotes={UNREAD}, }, @ARTICLE{RudenchikAug93, title={ Trapping and propagation of VLF waves in ducts: an analytical approach }, journal={Planetary and Space Science}, volume={41}, number={8}, year={1993}, month={Aug}, pages={619-31}, abstract={ Ray trapping into a duct can be described if one takes into account the fact that duct properties vary along the duct; otherwise the paths of the duct-trapped rays are periodical. An advanced theory is devoted to an analytical description of ray propagation in ducts and other waveguides with parameters varying along their length. Conditions of waveguide propagation are defined for the case when the plasma gradients inside a duct are comparable with the ambient gradients. The angles of ray trapping into ducts of arbitrary profile have been calculated. Explicit expressions for ray traces in a duct of parabolic profile have been found. Examples of charts for critical angles of whistler trapping into ionospheric and magnetospheric ducts are also presented }, keywords={ atmospheric structure electron density ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation plasma whistlers ionosphere ducts VLF waves trapping duct plasma density gradients VLF waves propagation ambient plasma density gradients ray trapping angles duct-trapped rays paths duct parabolic profile ray propagation waveguide propagation ray traces critical angles whistler trapping magnetospheric ducts 3 to 30 kHz }, mynotes={UNREAD}, }, @ARTICLE{RycroftSep91, title={ Interactions between whistler-mode waves and energetic electrons in the coupled system formed by the magnetosphere, ionosphere and atmosphere }, journal={J. Atmos. Terr. Phys. (UK), Journal of Atmospheric and Terrestrial Physics}, volume={53}, number={9}, year={1991}, month={Sep}, pages={849-58}, abstract={ The physical mechanism of a cyclotron resonance interaction between trapped energetic electrons and whistler-mode waves in the magnetosphere is discussed. Not only do the electrons have their pitch angles reduced in this interaction, so that they may be precipitated into the upper atmosphere, but also the waves can be amplified. Such a flux of precipitating electrons can, either by direct ionisation or via bremsstrahlung radiation, cause a pimple to be produced on the bottom of the ionosphere. That can significantly modify the amplitude and/or phase of very low frequency radio signals propagating in the Earth-ionosphere waveguide. Various experimental observations that demonstrate the reality of such effects are reviewed }, keywords={ atmospheric electron precipitation magnetospheric electromagnetic wave propagation whistlers EM wave particle interaction electron precipitation VLF whistler-mode waves energetic electrons coupled system magnetosphere ionosphere atmosphere physical mechanism cyclotron resonance interaction pitch angles pimple very low frequency }, mynotes={UNREAD}, }, @ARTICLE{SaMar88, author={Sa, L.A.D. and Helliwell, R.A.}, title={ Structure of VLF whistler mode sideband waves in the magnetosphere }, journal={Journal of Geophysical Research}, volume={93}, number={A3}, year={1988}, month={Mar}, pages={1987-92}, abstract={ An accurate determination is made of the sideband structure of ducted VLF whistler mode waves transmitted from Siple Station and observed at Lake Mistissini, Quebec. Single- and double-frequency experiments are described. It is shown that sideband spectra can be explained by nonlinear interactions between two or more lines in the magnetosphere, the line intensities required for such interactions being low. If one of the lines is a transmitted carrier, the other line can be as much as 40 dB lower in amplitude, implying that power line radiation (PLR) can be an important factor in sideband generation. It is shown that 'single-line' sidebands are due to interactions between the input wave and harmonics of 60 Hz present within the duct (assumed to be PLR), and that double-line spectra are affected by their position relative to the same 60-Hz system of lines. A study of double-line spectra as a function of line separation and line amplitude ratio is made }, keywords={ magnetospheric electromagnetic wave propagation radiowave propagation whistlers radiowave atmosphere VLF whistler mode sideband waves magnetosphere spectra nonlinear interactions line intensities power line radiation harmonics duct double-line spectra separation amplitude ratio }, mynotes={UNREAD}, }, @ARTICLE{SaAug90, title={ A wave-particle-wave interaction mechanism as a cause of VLF triggered emissions }, journal={Journal of Geophysical Research}, volume={95}, number={A8}, year={1990}, month={Aug}, pages={12277-86}, abstract={ Presents a narrowband-filter spectral analysis of VLF emissions triggered by discrete waves transmitted from Siple Station, Antarctica and received at Lake Mistissini, Quebec, after ducted mode propagation. Triggered emissions have a spectral structure similar to magnetospheric sidebands. As in the case of regular sidebands, their spectra and evolution are affected by the presence of power line radiation (PLR). Triggered emissions associated with monochromatic wave transmissions are caused by the interaction of the incoming wave with PLR. The importance of extremely weak signals in these phenomena is discussed; and it is shown that when a wave is perturbed by a weaker signal, sidebands and, consequently, triggered emissions can occur even if the amplitude ratio of the two signals is -50 dB. For such cases, the two waves should not be separated by a frequency larger than a few times the trapping frequency of the stronger wave }, keywords={ atmospheric radiation atmospheric spectra atmospherics magnetosphere plasma signals amplitude ratio ELF PLH frequencies incoming wave-PLR interaction single-frequency pre-termination triggering equal-amplitude double-frequency pre-termination triggering unequal-amplitude triggering magnetosphere hot electrons wave-particle-wave interaction mechanism VLF triggered emissions narrowband-filter spectral analysis Siple Station Antarctica Lake Mistissini Quebec ducted mode propagation spectral structure magnetospheric sidebands power line radiation monochromatic wave transmissions extremely weak signals trapping frequency stronger wave 1.0 to 4.0 kHz 60 Hz 2.1 kHz 1980 Hz 2340 Hz }, mynotes={UNREAD}, }, @ARTICLE{SaOct89, title={ A cyclotron resonance mechanism for very-low-frequency whistler-mode sideband wave radiation. II. Description of internal ('trapped') resonances }, journal={Journal of Applied Physics}, volume={66}, number={8}, year={1989}, month={Oct}, pages={3495-505}, abstract={ For pt.I see ibid., vol.66, p.3482 (1989). The second part of the paper presents an analytical and numerical treatment of cyclotron resonances formed inside the potential wells of a set of monochromatic carriers propagating in a duct in the magnetosphere. It is found that those resonances produce oscillatory disturbances in the potential well charge distribution that frequency modulate the carriers to produce sidebands. The frequency spectrum is the same as the one generated by the external resonances defined in part I. The carrier trapping frequencies do not affect the sideband wave frequencies and do not impose sharp constraints on the spectrum bandwidth, on the sideband line separation, or on the maximum interacting carrier frequency separation. When not highly distorted by wave growth, a two-carrier sideband spectrum should have an approximately exponential profile }, keywords={ atmospherics magnetospheric electromagnetic wave propagation whistlers internal resonances cyclotron resonance very-low-frequency whistler-mode sideband wave radiation duct magnetosphere }, mynotes={UNREAD}, }, @ARTICLE{SakamotoMay95, author={Sakamoto, K. and Kasahara, Y. and Kimura, I.}, title={ K-vector determination of whistler mode signals by using amplitude data obtained by a spacecraft borne instrument }, journal={IEEE Transactions on Geoscience and Remote Sensing}, volume={33}, number={3}, year={1995}, month={May}, pages={528-34}, abstract={ A straightforward method for determination of k-vector (wave normal) direction of a whistler mode signal observed onboard spacecraft consists in measuring three components of the wave magnetic field with their instantaneous amplitudes and phases. In that method, one needs to send by telemetry a total wave form of a signal, which requires much larger bandwidth than for sending amplitudes only. The present study develops another method of determination of the wave normal direction based only on the amplitude data; the method is checked using Omega signal observations by the Akebono satellite. It should, however, be noted that the sense of k-vector is not determined by this proposed method }, keywords={ atmospheric techniques direction-of-arrival estimation ionosphere ionospheric electromagnetic wave propagation ionospheric techniques magnetosphere magnetospheric electromagnetic wave propagation radiowave propagation radiowaves whistlers atmosphere magnetosphere ionosphere radiowave whistler measurement technique K-vector determination direction of arrival whistler mode signals amplitude data spacecraft borne instrument method wave normal direction Omega signal observations Akebono satellite }, mynotes={UNREAD}, }, @ARTICLE{SantolikMay96, author={Santolik, O. and Parrot, M.}, title={ The wave distribution function in a hot magnetospheric plasma: the direct problem }, journal={Journal of Geophysical Research}, volume={101}, number={A5}, year={1996}, month={May}, pages={10639-51}, abstract={ Studying electromagnetic waves in a magnetospheric plasma, it is often important to find their directions of propagation. When the assumption of a plane wave is not valid, the determination of the wave distribution function (WDF) is required. The WDF specifies the distribution of wave-energy density with respect to the frequency and the wave-normal direction. An alternative approach to the estimation of the experimentally accessible data for a given WDF is suggested with the hot-plasma and/or Doppler effects taken into account. The method is based on an explicit frequency dependence of the WDF. Examples of solutions, including the determination of the wave-refractive index, the wave-growth rate, the group velocity, and theoretical predictions of experimental data at predefined frequencies, are given in different cases. First, whistler-mode waves in a hot plasma near the geostationary orbit were studied. Second, the low-frequency waves observed by the low-altitude satellite Freja in the auroral zone were subjected to theoretical analysis. A complex, multimodal structure of the wave characteristics was found, mainly around the resonance angle. In the case of extremely short-wavelength waves, the influence of the Doppler effect produced qualitative changes of the wave-normal dependence of wave parameters }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation plasma waves whistlers wave distribution function hot magnetospheric plasma direct problem wave-energy density wave-normal direction frequency dependence wave-refractive index wave-growth rate group velocity whistler-mode waves low-frequency waves auroral zone multimodal structure resonance angle extremely short-wavelength waves Doppler effect wave-normal dependence wave parameters }, mynotes={UNREAD}, }, @ARTICLE{SatoJun90, author={Sato, N. and Suzuki, H. and Maezawa, K. and Saemundsson, T.}, title={ Conjugacy of daytime ELF-VLF emission activities in the auroral zones }, journal={Journal of Geophysical Research}, volume={95}, number={A6}, year={1990}, month={Jun}, pages={7847-56}, abstract={ Statistical characteristics of emission occurrence are examined, using 1 year of digital data of 750-Hz, 2-kHz, and 4-kHz intensity records. These waves were measured simultaneously at a conjugate pair of stations, namely Syowa Station in Antarctica and Husafell in Iceland. The following notable diurnal and seasonal variation and Kp dependence was found for the daytime emissions (04-14 MLT): (1) The 750-Hz emissions were mostly observed during the daytime around noon in both conjugate regions. The emission occurrence reached a maximum 1-3 hours earlier at Syowa than at Husafell during the equinox season. The seasonal variation of 750-Hz emission occurrence showed a maximum during local summer and a minimum during local winter at both stations. (2) The 2-kHz emission occurrence reached a maximum around 13 MLT at Syowa and around 11 MLT at Husafell. Peaks of the emission occurrence during summer shifted to the afternoonside at Syowa and to the morningside at Husafell. The occurrences at Syowa reached a maximum during local summer and a minimum during winter. Further observational findings are reported }, keywords={ atmospheric radiation magnetosphere ELF VLF daytime radiowave emission conjugacy, conjugate emission activity diurnal variation AD 1984 AD 1985 magnetosphere auroral zones emission occurrence seasonal variation Kp dependence 750 to 4000 kHz }, mynotes={UNREAD}, }, @ARTICLE{SawadaFeb91, author={Sawada, A. and Kishi, Y. and Yamamoto, M. and Sakurai, A. and Kasahara, Y. and Kimura, I.}, title={ Propagation characteristics of Omega signals and their triggered emissions observed by EXOS-D satellite }, journal={Geophysical Research Letters}, volume={18}, number={2}, year={1991}, month={Feb}, pages={321-4}, abstract={ Omega signals have been frequently observed by the Japanese satellite EXOS-D (Akebono) in the magnetosphere. The authors have statistically analyzed VLF-WBA (wide-band analyzer) data in a period of 6 months, which were acquired by Kagoshima (KSC) and Prince Albert (PA) satellite tracking stations. About a quarter of the data obtained at KSC contain Omega signals from Australia and about a sixth of the data at PA contain those from North Dakota. Ray tracing calculations for the Australian Omega signals are consistent with the results of observations. 10 cases of triggered emissions are also found in the analyzed data }, keywords={ atmospheric radiation magnetosphere magnetospheric electromagnetic wave propagation radiowave emissions VLF propagation magnetosphere AD 1989 radiosignal Omega signals triggered emissions 10 to 14 kHz }, mynotes={UNREAD}, }, @ARTICLE{SawadaJul93, author={Sawada, A. and Nobata, T. and Kishi, Y. and Kimura, I. and Oya, H.}, title={ Electron density profile in the magnetosphere deduced from in situ electron density and wave normal directions of Omega signals observed by the Akebono (EXOS D) satellite }, journal={Journal of Geophysical Research}, volume={98}, number={A7}, year={1993}, month={Jul}, pages={11267-74}, abstract={ A new method is described for the construction global plasma distribution in the plasmasphere using the electron density measured along the trajectory of the Akebono (EXOS D) satellite and the wave normal direction of Omega signals simultaneously observed by the same spacecraft. In this method the plasma density distribution is described by using the diffusive equilibrium model, with eight parameters, that is, the relative abundances and temperatures of ions, and the electron density at a reference altitude. This model is first fit in a least squares sense to the electron density observed along the spacecraft trajectory. The fit solution is not always unique. Therefore the authors ray trace Omega signals from their source location and check if the wave normal directions at the spacecraft location are consistent with those observed }, keywords={ atmospheric techniques ionospheric techniques magnetosphere global distribution spatial distribution EXOS-D measurement technique magnetosphere wave normal directions Omega signals method plasma distribution plasmasphere satellite diffusive equilibrium model }, mynotes={UNREAD}, }, @ARTICLE{SazhinMay92, author={Sazhin, S.S. and Hayakawa, M.}, title={ Magnetospheric chorus emissions: a review }, journal={Planetary and Space Science}, volume={40}, number={5}, year={1992}, month={May}, pages={681-97}, abstract={ A review of chorus emissions observed at ground-based stations and in the Earth's magnetosphere is presented. Different approaches to modelling these emissions are discussed. It is pointed out that the most likely energy source of chorus emissions lies in the anisotropic hot electrons in the equatorial magnetosphere. The energy of these electrons is transferred to waves via the electron cyclotron instability. Then the nonlinear deformation of the hot electron distribution function under the influence of these waves produces almost monochromatic wavelets, which, in their turn, generate a chorus element in a manner similar to the generation of artificially stimulated emissions by ground-based transmitters }, keywords={ atmospheric radiation atmospherics electrons magnetosphere plasma radiation belts reviews magnetospheric chorus emissions VLF chorus emissions energy source ELF wave-particle interactions polar chorus midlatitude chorus auroral chorus rising frequency chorus anisotropic hot electrons equatorial magnetosphere electron cyclotron instability nonlinear deformation hot electron distribution function monochromatic wavelets artificially stimulated emissions ground-based transmitters 0.4 to 1.5 kHz 1 to 40 keV 100 to 500 Hz 1 to 5 kHz 6 to 9 kHz }, mynotes={UNREAD}, }, @ARTICLE{SazhinJun89, author={Sazhin, S.S. and Strangeways, H.J.}, title={ Ray-tracing in an inhomogeneous plasma }, journal={Planetary and Space Science}, volume={37}, number={6}, year={1989}, month={Jun}, pages={739-47}, abstract={ Two methods for ray-tracing in a linearly stratified plasma, which have applications for magnetospheric and/or astrophysical conditions are suggested. The application of these methods to the problem of whistler-mode propagation is considered in detail. The expression for a wave-normal angle theta /sub l/, for which changes in theta are not accompanied by changes in the ray direction, is derived. Application of this result to the interpretation of emissions with an inverted V-shape to the upper boundary of their spectrograms, seen by satellites in the topside ionosphere, is discussed }, keywords={ astrophysical plasma electromagnetic wave propagation in plasma magnetospheric electromagnetic wave propagation magnetosphere EM wave propagation inhomogeneous plasma ray-tracing linearly stratified plasma astrophysical conditions whistler-mode propagation wave-normal angle emissions spectrograms }, mynotes={UNREAD}, }, @ARTICLE{SazhinMar85, author={Sazhin, S.S. and Sazhina, E.M.}, title={ Quasielectrostatic whistler-mode propagation }, journal={Planetary and Space Science}, volume={33}, number={3}, year={1985}, month={Mar}, pages={295-303}, abstract={ An approximate formula is derived for the refractive index of a whistler-mode wave propagation in a hot anisotropic plasma with wave normal angle close to the resonance cone angle ( theta /sub R/). Approximations used during the derivation are generally satisfied for magnetospheric conditions. It is pointed out that the derived formula can be considered to be complementary to the corresponding formula for quasilongitudinal whistler-mode propagation in a hot anisotropic plasma which was derived by Sazhin and Sazhina (1982). The limits of applicability of a cold plasma model when determining the height of generation of saucer emissions and V-shaped hiss are discussed }, keywords={ magnetospheric electromagnetic wave propagation whistlers EM wave propagation quasielectrostatic magnetosphere approximate formula refractive index whistler-mode wave propagation hot anisotropic plasma saucer emissions V-shaped hiss }, mynotes={UNREAD}, }, @ARTICLE{SazhinApr82, author={Sazhin, S.S. and Sazhina, E.M.}, title={ Oblique whistler-mode propagation in a hot anisotropic plasma }, journal={Journal of Plasma Physics}, volume={27}, number={}, year={1982}, month={Apr}, pages={199-204}, abstract={ An approximate dispersion relation is obtained for quasi-longitudinal whistler mode propagation in the hot anisotropic plasma. The influence of plasma temperature and anisotropy on whistler energy focusing along the magnetic field and whistler trapping in the magnetospheric ducts are considered for the case when the whistler wave normal angle is not equal to zero }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation plasma temperature whistlers oblique quasilongitudinal focusing ionosphere whistler-mode propagation hot anisotropic plasma plasma temperature whistler energy whistler trapping magnetospheric ducts whistler wave }, mynotes={UNREAD}, }, @ARTICLE{SazhinJul93, author={Sazhin, S.S. and Bognar, P. and Smith, A.J. and Gy Tarcsai}, title={ Magnetospheric electron temperatures inferred from whistler dispersion measurements }, journal={Annales Geophysicae}, volume={11}, number={7}, year={1993}, month={Jul}, pages={619-23}, abstract={ Electron temperatures in the vicinity of the magnetospheric equator have been estimated from dispersion measurements on 24 whistlers observed and digitally recorded at Halley, Antarctica (76 degrees S, 27 degrees W; L=4.3) on 9 August 1989 between 1616 UT and 1707 UT, following a several-day period of moderately quiet geomagnetic conditions. The method previously described by Sazhin et al. (1990) was used with various models of electron density and temperature distribution along a field line, based on Park's (1972) DE-1 and DE-2 models. Uncertainties in the estimated temperatures were of the same order as the temperature values themselves, as result of small measurement errors in the whistler nose frequency and group time, and this limits the practical usefulness of the method, in its present state of development, as a diagnostic technique for inferring magnetospheric electron temperatures }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation whistlers magnetospheres electron temperature equatorial AD 1989 08 09 plasmasphere whistler dispersion equator nose frequency }, mynotes={UNREAD}, }, @ARTICLE{SazhinJan91, author={Sazhin, S.S. and Bullough, K. and Smith, A.J. and Saxton, J.M.}, title={ The influence of the ring current on whistler group delay time in the magnetosphere }, journal={Annales Geophysicae. Atmospheres, Hydrospheres and Space Sciences}, volume={9}, number={1}, year={1991}, month={Jan}, pages={21-9}, abstract={ An approximate analytical model of the magnetic field of the ring current is proposed. This field is assumed to be perpendicular to the magnetic dipole equator with its value depending on the crossing point distance of the field line from the centre of the Earth (r/sub 0/) and the D/sub st/ index measured at the Earth's surface near the equator. This model of the magnetic field of the ring current is used to obtain an estimate of the perturbation of whistler-mode group velocity and group delay time due to the ring current. An explicit expression for the perturbation of whistler-mode group delay time is derived in the form of a simple integral }, keywords={ magnetospheric electromagnetic wave propagation whistlers radiowave propagation VLF ring current whistler group delay time magnetosphere approximate analytical model magnetic field whistler-mode group velocity perturbation 3 to 30 kHz }, mynotes={UNREAD}, }, @ARTICLE{SazhinApr85, author={Sazhin, S.S. and Hayakawa, M. and Tanaka, Y.}, title={ On the fine structure of the ground-based VLF chorus as an indicator of the wave particle interaction processes in the magnetospheric plasma }, journal={Planetary and Space Science}, volume={33}, number={4}, year={1985}, month={Apr}, pages={385-6}, abstract={ Smirnova (1984) pointed out that chorus emissions can be used as a diagnostic tool for determinating several magnetospheric plasma parameters including the L-shell of chorus generation, the large scale electric field and the anisotropy of magnetospheric electrons. The author presents three comments on the corresponding methods of diagnostics proposed by Smirnova }, keywords={ atmospheric electricity atmospheric techniques atmospherics magnetosphere plasma AD 1978 11 to 1978 01 atmospherics electrons atmospheric technique fine structure VLF chorus wave particle interaction magnetospheric plasma L-shell electric field }, mynotes={UNREAD}, }, @ARTICLE{SazhinApr90, author={Sazhin, S.S. and Smith, A.J. and Sazhina, E.M.}, title={ Can magnetospheric electron temperature be inferred from whistler dispersion measurements? }, journal={Annales Geophysicae. Atmospheres, Hydrospheres and Space Sciences}, volume={8}, number={4}, year={1990}, month={Apr}, pages={273-86}, abstract={ An approximate expression for whistler-mode group velocity is obtained, taking into account the effects of electron temperature and anisotropy, density and ion effects, effects of oblique propagation and the non-dipolarity of the dayside magnetospheric magnetic field. This expression is applied to the propagation of whistlers between one hemisphere and the other. At frequencies close to the upper cut-off of whistler spectra, perturbations to whistler group delay times due to temperature effects can be of the same order of magnitude as, or even higher than, the corresponding perturbations due to finite electron density and ion effects. A method of magnetospheric electron temperature diagnostics is proposed and applied to two whistlers recorded at Halley (L=4.3). The values of temperature obtained from the analysis of whistler spectra depend on the choice of model of electron density and temperature distribution in the magnetosphere and on the effect of ducted ray path on whistler delay times }, keywords={ atmospheric techniques atmospheric temperature dispersion (wave) magnetosphere magnetospheric electromagnetic wave propagation plasma whistlers magnetospheric whistlers interhemispheric propagation VLF temperature anisotropy effects oblique propagation effects finite electron density effects nondipolar magnetic field whistlers upper cut-off frequencies Halley Base ELF Antarctica delay times perturbations AD 1977 06 24 whistler dispersion measurements whistler-mode group velocity dayside magnetospheric magnetic field whistler spectra whistler group delay times ion effects magnetospheric electron temperature diagnostics whistler spectra 2 to 18 kHz }, mynotes={UNREAD}, }, @ARTICLE{SazhinJan92, author={Sazhin, S.S. and Smith, A.J. and Bullough, K. and Clilverd, M.A. and Saxton, J.M. and Strangeways, H.J. and Tarcsai, G.}, title={ Group delay times of whistler-mode signals from VLF transmitters observed at Faraday, Antarctica }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={54}, number={1}, year={1992}, month={Jan}, pages={99-107}, abstract={ The group delay times (t/sub g/) of whistler-mode waves generated by the NAA (f=24.0 kHz) and NSS (f=21.4 kHz) U.S. Navy transmitters and recorded at Faraday, Antarctica (L=2.3), after following a ducted field-aligned path are analysed theoretically for different L-shells of propagation using models of electron density, temperature, and ion composition distribution for typical day and night-time conditions. t/sub g/ is presented as the sum of (1) a group delay time calculated for the simplest model of wave propagation parallel to the magnetic field in a cold, dense plasma with the effects of ions neglected (t/sub g0/) and (2) the corrections due to finite electron density, that is, finite ratio of electron plasma frequency to electron gyrofrequency ( Delta t/sub gc/), contribution of ions ( Delta t/sub gr/), and non-zero electron temperature ( Delta t/sub gh/). It is pointed out that the correction Delta t/sub gc/ is the dominant one, while the ratio Delta t/sub gh// Delta t/sub gc/ is only about 1% for L close to 2.3. The total correction Delta t/sub gs/= Delta t/sub gc/+ Delta t/sub gr/+ Delta t/sub gh/ at L=2.3 is about 10 ms and is to be taken into account when interpreting the measurements of t/sub g/ }, keywords={ magnetospheric electromagnetic wave propagation whistlers group delay time radiowave propagation whistler-mode signals VLF Faraday Antarctica ducted field-aligned path L-shells 21 to 24 kHz }, mynotes={UNREAD}, }, @ARTICLE{SazhinSep90, author={Sazhin, S.S. and Walker, S.N. and Woolliscroft, L.J.C.}, title={ On whistler-mode trapping in the vicinity of the Earth's magnetopause }, journal={Annales Geophysicae. Atmospheres, Hydrospheres and Space Sciences}, volume={8}, number={9}, year={1990}, month={Sep}, pages={583-8}, abstract={ AMPTE-UKS observations are used to show that the intensification of whistler-mode waves observed near the earthward boundary of the Earth's magnetopause can be related to wave trapping in this region }, keywords={ magnetosphere plasma waves whistlers ELF VLF whistler-mode trapping Earth's magnetopause AMPTE-UKS observations intensification wave trapping }, mynotes={UNREAD}, }, @ARTICLE{SazhinMar90a, author={Sazhin, S.S. and Walker, S.N. and Woolliscroft, L.J.C.}, title={ On spin-modulation diagnostics of whistler-mode wave normal angles in the vicinity of the Earth's magnetopause }, journal={Planetary and Space Science}, volume={38}, number={3}, year={1990}, month={Mar}, pages={333-9}, abstract={ A theoretical analysis of spin-modulation effects on wave power measurements of whistler-mode waves observed onboard the APTE-UKS satellite in the vicinity of the day-side magnetopause is presented. Based on this analysis it is concluded that the observed waves were propagating almost parallel to the magnetic field }, keywords={ magnetospheric electromagnetic wave propagation whistlers wave normal angle whistler wave magnetosphere propagation spin-modulation diagnostics magnetopause wave power }, mynotes={UNREAD}, }, @ARTICLE{SazhinMay91, title={ Whistler-mode polarization in a rarefied plasma }, journal={Planetary and Space Science}, volume={39}, number={5}, year={1991}, month={May}, pages={725-8}, abstract={ Approximate expressions for whistler-mode polarization taking into account the effect of finite electron density, the contribution of ions, and the effect of nonzero electron temperature are derived in a form convenient for practical applications. These expressions are particularly important for the study of whistler-mode polarization in a rarefied magnetosphere plasma where the electron plasma frequency is not well above the electron gyrofrequency }, keywords={ atmospherics electromagnetic wave polarisation magnetosphere magnetospheric electromagnetic wave propagation plasma whistlers whistler-mode propagation ion density quasi-longitudinal approximations whistler-mode polarization finite electron density nonzero electron temperature rarefied magnetosphere plasma electron plasma frequency electron gyrofrequency }, mynotes={UNREAD}, }, @ARTICLE{SazhinOct91, title={ Landau damping of low frequency whistler-mode waves }, journal={Annales Geophysicae. Atmospheres, Hydrospheres and Space Sciences}, volume={9}, number={10}, year={1991}, month={Oct}, pages={690-5}, abstract={ An expression is derived for the growth ( gamma >0) and damping ( gamma <0) coefficients of whistler-mode waves in a hot plasma for waves propagating at an angle to the external magnetic field, on the assumption that the propagation itself is unaffected by the finite electron temperature. In the case of a Maxwellian distribution of the electrons with respect to velocities parallel to the magnetic field, the expression for gamma predicts rather strong damping of oblique whistler-mode waves unless their wave normal angles are close to zero. This means that only waves propagating almost parallel to the magnetic field are likely to be excited due to the temperature anisotropy of the electrons (T/sub perpendicular to />T/sub ///), and this should be taken into account when interpreting observations of natural whistler-mode radio emissions in the Earth's magnetosphere. It is pointed out that Landau damping (or the corresponding instability) of the waves under consideration results mainly from the energy exchange between the electrons and the component of the wave electric field parallel to the external magnetic field B/sub 0/. The energy exchange between the electrons and the component of the wave electric field perpendicular to B/sub 0/ mainly contributes to the cyclotron damping or growth of the waves, although the role of this process in Landau damping (or the corresponding instability) may not be negligibly small }, keywords={ magnetosphere plasma waves whistlers magnetosphere Landau damping low frequency whistler-mode waves hot plasma external magnetic field electron temperature radio emissions Earth's magnetosphere instability energy exchange electric field cyclotron damping }, mynotes={UNREAD}, }, @ARTICLE{SazhinMar90b, title={ Storey angle for whistler-mode waves }, journal={Planetary and Space Science}, volume={38}, number={3}, year={1990}, month={Mar}, pages={327-31}, abstract={ The concept of the Storey angle, i.e. the angle of maximal deviation of the direction of whistler-mode group velocity from the magnetic field, is generalized for the case of a finite ratio of wave frequency to electron gyrofrequency with the effects of finite electron density, the contribution of ions, non-zero electron temperature and anisotropic character of their distribution function being taken into account }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation whistlers plasma wave radiowave propagation magnetosphere ionosphere whistler-mode waves Storey angle maximal deviation direction }, mynotes={UNREAD}, }, @ARTICLE{SazhinNov89, title={ A physical model of quasi-electrostatic whistler-mode propagation }, journal={Astrophysics and Space Science}, volume={161}, number={1}, year={1989}, month={Nov}, pages={171-4}, abstract={ The process of quasi-electrostatic whistler-mode propagation is interpreted in terms of the periodic energy exchange between the wave field and the perturbed electron currents }, keywords={ atmospheric electricity atmospherics electromagnetic wave propagation in plasma magnetosphere magnetospheric electromagnetic wave propagation plasma plasma oscillations whistlers magnetosphere radio emissions whistler-mode EM waves cold ion-electron plasma hot anisotropic plasma wave-electric field component Langmuir oscillations quasi-electrostatic whistler-mode propagation periodic energy exchange wave field perturbed electron currents }, mynotes={UNREAD}, }, @ARTICLE{SazhinMar89, title={ On quasilongitudinal approximations for whistler-mode waves in a hot plasma }, journal={Planetary and Space Science}, volume={37}, number={3}, year={1989}, month={Mar}, pages={295}, abstract={ In a paper of Singh and Singh (ibid., vol.34, p.337, (1986)) it was claimed that the dispersion equation for quasilongitudinal whistler-mode propagation in a hot isotropic Maxwellian plasma can be written as: N/sup 2/=1+( Pi /sup 2//kw omega )Z( xi ) -(1), where: xi = omega - Omega cos theta /kw -(2), Z( xi ) is the plasma dispersion function, w is the electron thermal velocity, k is the wave number, N is the wave refractive index, omega is the wave frequency, Pi and Omega >0 are the electron plasma frequency and gyrofrequency respectively, theta is the wave normal angle. The present author discusses the invalidity of equation (1) }, keywords={ magnetospheric electromagnetic wave propagation plasma plasma waves whistlers plasma wave magnetosphere EM wave quasilongitudinal approximations whistler-mode waves hot plasma dispersion equation quasilongitudinal whistler-mode propagation }, mynotes={UNREAD}, }, @ARTICLE{SazhinJul88, title={ Oblique whistler-mode growth and damping in a hot anisotropic plasma }, journal={Planetary and Space Science}, volume={36}, number={7}, year={1988}, month={Jul}, pages={663-7}, abstract={ An expression for the oblique whistler-mode increment of instability or decrement of damping gamma in a hot anisotropic plasma is derived in a form convenient for practical applications, e.g. in magnetospheric conditions. It is pointed out that small thermal corrections to the value of the quasilongitudinal whistler-mode refractive index result in considerable (up to several orders of magnitude) changes of the value of gamma and can even change the sign of gamma }, keywords={ atmospherics magnetosphere magnetospheric electromagnetic wave propagation plasma whistlers magnetosphere EM wave amplification oblique whistler-mode growth oblique whistler-mode damping decrement whistler instability increment hot anisotropic plasma magnetospheric conditions thermal corrections quasilongitudinal whistler-mode refractive index }, mynotes={UNREAD}, }, @ARTICLE{SazhinApr88, title={ On the polarization of quasielectrostatic whistler-mode waves in the magnetospheric plasma }, journal={Annales Geophysicae. Atmospheres, Hydrospheres and Space Sciences}, volume={6}, number={2}, year={1988}, month={Apr}, pages={177-9}, abstract={ The quasielectrostatic whistler-mode polarization at oblique resonance for a cold plasma, is analysed analytically. The plasma is assumed to consist of species with different temperatures and anisotropies which well approximate magnetospheric conditions }, keywords={ magnetospheric electromagnetic wave propagation plasma whistlers magnetosphere EM wave polarisation polarization quasielectrostatic whistler-mode waves oblique resonance cold plasma }, mynotes={UNREAD}, }, @ARTICLE{SazhinApr86, title={ On whistler-mode group velocity }, journal={Annales Geophysicae, Series A (Upper Atmosphere and Space Sciences)}, volume={4}, number={2}, year={1986}, month={Apr}, pages={155-60}, abstract={ An analytical analysis of the group velocity of whistler-mode waves propagating parallel to the magnetic field in a hot anisotropic plasma is presented. Some simple approximate formulae, which can be used for the magnetospheric applications, are derived. These formulae can predict some properties of this group velocity which were not previously recognized or were obtained by numerical methods. In particular, it is pointed out that the anisotropy tends to compensate for the influence of the electron temperature on the value of the group velocity when the wave frequency is well below the electron gyrofrequency. It is predicted, that under certain conditions, at frequencies near the electron gyrofrequency, this velocity tends towards zero }, keywords={ magnetospheric electromagnetic wave propagation whistlers EM wave radiowave propagation magnetosphere whistler-mode group velocity hot anisotropic plasma approximate formulae }, mynotes={UNREAD}, }, @ARTICLE{SazhinJun84, title={ On whistler-mode trapping in the magnetospheric ducts }, journal={Journal of Plasma Physics}, volume={31}, number={}, year={1984}, month={Jun}, pages={487-93}, abstract={ Conditions for whistler-mode trapping in the magnetospheric ducts are considered. The plasma model included electron temperature and anisotropy, and there are no restrictions on the value of the wave normal angle. It is pointed out that the range of the wave normal angles for which whistler-mode waves can be trapped in the ducts with enhanced electron density increases when the electron temperature and (or) anisotropy increases; the corresponding increase also takes place for the average wave normal angle when whistler-mode waves are trapped in the ducts that have a deficiency in electron density. The limits of applicability of a simplified formula derived by Sazhin and Sazhina (1982) for whistler-mode propagation is a hot anisotropic plasma, are clarified }, keywords={ electron density magnetospheric electromagnetic wave propagation plasma density plasma instability plasma temperature plasma theory plasma waves radiowave propagation whistlers radiowave propagation EM wave whistler-mode trapping magnetospheric ducts plasma model electron temperature anisotropy wave normal angle enhanced electron density whistler-mode waves whistler-mode propagation }, mynotes={UNREAD}, }, @ARTICLE{SchwartzNov96, author={Schwartz, S.J. and Burgess, D. and Moses, J.J.}, title={ Low-frequency waves in the Earth's magnetosheath: present status }, journal={Annales Geophysicae}, volume={14}, number={11}, year={1996}, month={Nov}, pages={1134-50}, abstract={ The terrestrial magnetosheath contains a rich variety of low-frequency (1 temperature anisotropies and dominate when the plasma beta is low or high, respectively. Slow modes may also be present within a transition layer close to the subsolar magnetopause, although they are expected to suffer strong damping. All mode identifications are based on linearized theory in a homogeneous plasma and there are clear indications, in both the data and in numerical simulations, that nonlinearity and/or inhomogeneity modify even the most basic aspects of some modes. Additionally, the determination of the wave vector remains an outstanding observational issue }, keywords={ magnetohydrodynamic waves magnetosphere plasma waves whistlers magnetosheath low frequency waves Alfven waves ion cyclotron waves whistler waves magnetosonic waves mirror modes ion temperature anisotropic waves instabilities wave sources power spectra growth rate temperature anisotropy slow mode fast mode hybrid simulations }, mynotes={UNREAD}, }, @ARTICLE{ScourfieldJul84, author={Scourfield, M.W.J. and Rash, J.P.S. and Duthie, D.D.}, title={ Auroral pulsations-television image and VLF hiss correlation }, journal={Planetary and Space Science}, volume={32}, number={7}, year={1984}, month={Jul}, pages={809-17}, abstract={ The association between VLF hiss and auroral-light intensity has been studied for pulsating auroras by coordinated observations with a broad band VLF receiver and a low light level TV system viewing the N/sub 2//sup +/ ING emissions. Power spectral analyses of the VLF hiss and auroral-light intensity fluctuations display a common peak at 1.3+or-0.3 Hz. Cross-spectral analysis shows that the times of the peaks in the auroral-light intensity fluctuations differ from those of the VLF hiss by times ranging between zero and 0.2 s. This result is shown to be compatible with a cyclotron resonance interaction in the vicinity of the equatorial plane. The periodicity of the intensity fluctuations can be accounted for by assuming the process is driven by echoing VLF hiss which may be single-phase or three-phase }, keywords={ atmospheric electron precipitation atmospheric radiation atmospherics aurora magnetosphere VLF hiss time delay atmospherics magnetosphere atmospheric radiation plasmaspheric hiss single phase hiss three phase hiss power spectral analyses light intensity fluctuations frequency wave-particle interactions cross spectral analysis light intensity peak times electron precipitation AD 1975 09 10 auroral-light intensity pulsating auroras broad band VLF receiver low light level TV system N/sub 2//sup +/ ING emissions auroral-light intensity fluctuations cyclotron resonance interaction equatorial plane echoing VLF hiss }, mynotes={UNREAD}, }, @ARTICLE{SeylerOct96, author={Seyler, C.E. and Wahlund, J.-E.}, title={ Theory of nearly perpendicular electrostatic plasma waves and comparison to Freja satellite observations }, journal={Journal of Geophysical Research}, volume={101}, number={A10}, year={1996}, month={Oct}, pages={21795-813}, abstract={ The linear and nonlinear two-fluid nature of oblique electrostatic plasma waves is explored and clarified. It is found that two distinct wave regimes exist corresponding to propagation angles greater than or less than E= square root (m/sub e//m/sub 1/) with respect to the perpendicular direction of the magnetic field. Propagation angles greater than epsilon correspond to either the electrostatic ion cyclotron wave or the shorter wavelength oblique ion acoustic wave, which are termed the fast ion cyclotron and fast ion acoustic waves respectively. Angles less than E correspond to the inertial Alfven wave which is called the slow ion cyclotron wave and in the short wavelength limit is called the slow ion acoustic wave. The slow ion-acoustic wave is found to have a predominately ion-Boltzmann response. Initial value simulations having fast or slow ion cyclotron wave initial conditions of modest amplitudes result in nonlinear steepening and subsequent breakup into fast or slow ion acoustic waves respectively. This mechanism of ion acoustic wave generation may partially explain the origin of ion acoustic activity detected by the Freja satellite within regions of ion and electron acceleration }, keywords={ ionosphere plasma electrostatic waves ionosphere nearly perpendicular electrostatic plasma wave theory electrostatic wave Freja satellite observations topside nonlinear two-fluid nature oblique electrostatic plasma waves linear model propagation angle electrostatic ion cyclotron wave oblique ion acoustic wave fast ion cyclotron wave fast ion acoustic wave mechanism ion acoustic wave generation }, mynotes={UNREAD}, }, @ARTICLE{ShawhanOct85, title={ The menagerie of geospace plasma waves }, journal={Space Sci. Rev. (Netherlands), Space Science Reviews}, volume={42}, number={1-2}, year={1985}, month={Oct}, pages={257-74}, abstract={ Sounding rockets and satellites have discovered a large variety of plasma waves within the Earth's magnetosphere-geospace. These waves are found over a frequency range of millihertz to megahertz. The frequency ranges are generally associated with characteristic frequencies such as the plasma frequency and gyrofrequency. Most waves are generated by hot or streaming magnetospheric plasma; some waves are due to lightning discharges, to intentional man-made transmitters or to incidental radiation from power transmission systems. Propagation of waves from the observation region back to a probable source region can be modelled using ray tracing techniques in a model magnetosphere where the electron number density, ion composition and magnetic field vector is specified. Information in addition to the common amplitude-frequency-time spectrograms can be obtained from the received waves using multiple antennas and receivers. Cross-correlation of the wave electric and magnetic components can provide information on the wave polarization and direction of propagation and on the wave distribution function }, keywords={ magnetosphere plasma cross correlation plasma waves characteristic frequencies plasma frequency gyrofrequency magnetospheric lightning discharges man-made transmitters power transmission systems source region ray tracing electron number density ion composition magnetic field vector common amplitude-frequency-time spectrograms polarization direction wave distribution function }, mynotes={UNREAD}, }, @CONFERENCE{Shima94, author={Shima, N. and Hayakawa, M. and Ohta, K.}, title={ Lightning-induced precipitation based on the wave and particle measurements }, booktitle={1994 International Symposium on Electromagnetic Compatibility (IEEE Cat.No.94TH0680-9)}, volume={}, number={}, year={1994}, month={}, pages={705-8}, abstract={ Some energy of lightning discharges penetrates into the terrestrial magnetosphere, and interacts with energetic electrons in the radiation belt. Hence, lightning modifies the magnetosphere through wave-particle interaction. This interaction is studied by the combined measurement of particle precipitation and waves }, keywords={ electromagnetic interference ionospheric electromagnetic wave propagation lightning radiation belts radiowave propagation whistlers lightning induced precipitation particle measurement lightning discharges terrestrial magnetosphere radiation belt energetic electron wave-particle interaction particle precipitation wave measurements EM noise Trimpi events }, mynotes={UNREAD}, }, @ARTICLE{ShimakuraAug92, author={Shimakura, S. and Hayakawa, M.}, title={ Wave distribution functions of magnetospheric VLF waves with multiple field components: the effect of the polarization model in the integration kernels on the reconstruction of wave distribution functions }, journal={IEICE Trans. Fundam. Electron. Commun. Comput. Sci. (Japan), IEICETransactions on Fundamentals of Electronics, Communications and ComputerSciences}, volume={E75-A}, number={8}, year={1992}, month={Aug}, pages={1014-19}, abstract={ The wave distribution functions (WDFs) have been reconstructed by means of the maximum entropy inversion to the observed spectral matrix composed of the auto- and cross-power spectra among the three field components (Bx,By and Ez) in which the exactly right-handed circular polarization is taken in the integration kernels. The purpose of this paper is to investigate the properties of wave distribution functions reconstructed for wave sources whose central polarization is somewhat deviated from right-handed circular and to study: the WDF's by using the right-handed circular polarization in the kernels; the effect of larger deviations for the polarization of elementary plane waves constituting the wave source; the WDF's based on the elliptical polarization kernels; and the effect of limiting the number of eigenvalues. It is then found that changing the polarization model in the integration kernels would be helpful in finding out the polarization of the actually observed signals }, keywords={ electromagnetic wave polarisation magnetospheric electromagnetic wave propagation radio direction-finding radiowave propagation spectral analysis direction finding magnetospheric VLF waves multiple field components polarization model integration kernels wave distribution functions maximum entropy inversion spectral matrix right-handed circular polarization elliptical polarization kernels eigenvalues }, mynotes={UNREAD}, }, @ARTICLE{Shimakura86, author={Shimakura, S. and Okada, T. and Hayakawa, M. and Tanaka, Y.}, title={ The relationship between the polarization of whistlers and their dispersion }, journal={Journal of Geophysics}, volume={59}, number={2}, year={1986}, month={}, pages={140-1}, abstract={ It is found, based on the whistler data obtained at Moshiri, that there exists a definite relationship between the phase difference ( Phi ) of wave magnetic fields of daytime whistlers on two crossed loop aerials and the dispersion (D); Phi (deg)=-3.34*D(s/sup 1/2/)+82.2. This relation in conjunction with a previous empirical formula relating the dispersion with path latitude suggests a diagnostic tool for inferring the path latitude of VLF emissions by only using the simple polarization measurement for those waves }, keywords={ magnetospheric electromagnetic wave propagation whistlers EM wave propagation magnetosphere polarization whistlers dispersion phase difference daytime VLF }, mynotes={UNREAD}, }, @CONFERENCE{Shimakura94, author={Shimakura, S. and Smith, A.J. and Hayakawa, M.}, title={ Ground-based direction finding of VLF radio waves based on the wave distribution function: solution independent of wave polarisations }, booktitle={1994 International Symposium on Electromagnetic Compatibility (IEEE Cat.No.94TH0680-9)}, volume={}, number={}, year={1994}, month={}, pages={689-92}, abstract={ Discusses a method for estimating the wave distribution function (WDF) independently of the wave polarisation, which is an important technique for discuss the propagation and generation mechanisms of VLF radio waves, including magnetospheric VLF waves, tweek atmospherics, waves from a transmitter and so on. The new treatment used to estimate WDF solution of VLF waves observed on the ground is discussed. This is a very effective method because it is possible to estimate the WDF or wave energy distribution in wave number space. Computer simulation confirmed the effectiveness of this method, and also it is found from an analysis of VLF emissions that the ionospheric exit region moves very quickly }, keywords={ electromagnetic wave polarisation ionosphere ionospheric electromagnetic wave propagation ionospheric techniques magnetospheric electromagnetic wave propagation maximum entropy methods radio direction-finding radiowave propagation statistical analysis ground-based direction finding VLF radio waves wave distribution function radio waves propagation radio waves generation magnetospheric VLF waves tweek atmospherics transmitter wave energy distribution wave number space computer simulation VLF emissions ionospheric exit region maximum entropy method }, mynotes={UNREAD}, }, @ARTICLE{ShklyarDec92, author={Shklyar, D.R. and Nunn, D. and Smith, A.J. and Sazhin, S.S.}, title={ An investigation into the nonlinear frequency shift in magnetospherically propagated VLF pulses }, journal={Journal of Geophysical Research}, volume={97}, number={A12}, year={1992}, month={Dec}, pages={19389-402}, abstract={ When ducted narrow-band VLF pulses pass through the Earth's magnetosphere, small frequency shifts of approximately 1 Hz may be observed at the receiving site on the ground. Such shifts may be due to Doppler effects, but nonlinear electron cyclotron resonance near the magnetospheric equator may also play a part. This paper is a study of nonlinear frequency shifts induced by wave-particle interaction effects. The development assumes strong nonlinearity and the dominance of particle trapping. The VLF pulses are considered to be much shorter than the scale length of the interaction region; however, for long pulses the results remain valid for the front part of the pulse as seen at the receiving site }, keywords={ magnetospheric electromagnetic wave propagation radiowave propagation radiowave propagation nonlinear frequency shift magnetospherically propagated VLF pulses ducted narrow-band VLF pulses magnetosphere nonlinear electron cyclotron resonance wave-particle interaction effects }, mynotes={UNREAD}, }, @ARTICLE{ShyutteJan89, author={Shyutte, N.M. and Izhovkina, N.I.}, title={ Dynamics of resonance charged particles in the field of cyclotron electromagnetic waves }, journal={Kosmicheske Issledovaniya}, volume={27}, number={1}, year={1989}, month={Jan}, pages={71-5}, abstract={ Calculations are performed which suggest that the energy spectra of electrons and ions with 'spikes' on the tail of the distribution function observed by satellites in the upper ionosphere may develop from the multiple passage of charged particles through regions of resonance interaction with cyclotron electromagnetic waves }, keywords={ atmospheric electron precipitation atmospheric ion precipitation atmospherics ionosphere magnetosphere plasma radiation belts wave-particle resonance interactions inner magnetosphere resonant charged particles dynamics EM cyclotron waves ions energy spectra electrons energy spectra ionosphere energetic particle precipitation distribution function tail spikes resonance interaction regions quasi-monochromatic VLF radiation cyclotron electromagnetic waves upper ionosphere 27 keV 50 muT }, mynotes={UNREAD}, }, @ARTICLE{SinghOct92a, author={Singh, D.P. and Singh, U.P. and Singh, R.P.}, title={ Intensity peaks in low latitude VLF emissions observed at Ariel satellites }, journal={Planetary and Space Science}, volume={40}, number={10}, year={1992}, month={Oct}, pages={1425-30}, abstract={ A detailed analysis of low-latitude VLF emissions observed aboard the Ariel 3/4 satellites shows that some N-zone 3.2 kHz emissions are more intense than S-zone emissions. It is shown that these emissions are of an impulsive nature, and have their origin in lightning discharges in the S-zone. These emissions propagate to equatorial altitudes in the whistler mode, are amplified there by the cyclotron instability, and then, propagating the whistler mode, arrive at the Ariel satellites in the N-zone. Observations of VLF events and particle precipitation at lower L-shells support this conclusion }, keywords={ atmospheric elementary particle precipitation atmospherics lightning magnetosphere magnetospheric electromagnetic wave propagation plasma instability whistlers magnetospheric VLF emissions intensity peaks VLF atmospherics N-zone emissions impulsive VLF emissions VLF emissions amplification whistler mode propagation low-latitude precipitation low latitude VLF emissions Ariel satellites Ariel 3/4 satellites S-zone emissions lightning discharges 3.2 kHz }, mynotes={UNREAD}, }, @ARTICLE{SinghDec95, title={ Precipitation efficiency of coherent whistler mode waves during non-linear cyclotron resonance }, journal={Indian Journal of Radio & Space Physics}, volume={24}, number={6}, year={1995}, month={Dec}, pages={323-7}, abstract={ Non-linear cyclotron resonance between coherent whistler mode waves and energetic electrons is studied. It is found that there is a range of electron velocities, below and above which no interaction is possible. The maximum velocity of hot electrons (V/sub max/) decreases with increasing wave frequency, suggesting that lower frequencies are more able to drag energetic radiation belt electrons into the loss cone to be dumped into the lower ionosphere. The V- alpha space ( alpha being the resonant pitch angle) decreases as frequency and L value increase, but then the resonant pitch angle range increases. The precipitation efficiency is found to increase with L and wave frequency. The results are consistent with the findings of earlier workers and experimental observations recorded aboard Injun-3 and ATS-1 satellites }, keywords={ atmospheric electron precipitation radiation belts whistlers coherent whistler mode waves nonlinear cyclotron resonance precipitation efficiency electron velocities maximum velocity hot electrons wave frequency energetic radiation belt electrons lower ionosphere resonant pitch angle }, mynotes={UNREAD}, }, @ARTICLE{SinghOct92b, title={ Precipitated electron flux at low latitudes }, journal={Indian Journal of Radio & Space Physics}, volume={21}, number={5}, year={1992}, month={Oct}, pages={306-8}, abstract={ The cyclotron interaction between whistler mode waves and energetic electrons is studied for the latitudinal range 30-40 degrees , assuming an interacting wave of 5 kHz frequency and nonlinear pitch angle scattering. It is observed that the precipitation probability is highest at 36 degrees geomagnetic latitude. An explanation of this effect has been provided }, keywords={ atmospheric electron precipitation ionosphere magnetosphere whistlers wave-particle interactions aeronomy low-latitude electron precipitation precipitation probability latitude dependence VLF whistler wave frequency mirror height geomagnetic latitude 36 degrees to 40 degrees precipitating angle space width electron flux cyclotron interaction whistler mode waves energetic electrons nonlinear pitch angle scattering 36 degrees geomagnetic latitude 110 km 100 to 220 km }, mynotes={UNREAD}, }, @ARTICLE{SinghMar93, author={Singh, R.P. and Lalmani and Singh, U.P.}, title={ Discrete emissions and whistler precursors recorded at low latitude ground station Gulmarg }, journal={Earth, Moon, and Planets}, volume={60}, number={3}, year={1993}, month={Mar}, pages={225-32}, abstract={ Discrete chorus-type emission and whistler precursors recorded in March 1972 during daytime hours at the ground-based station Gulmarg are presented. It is shown that discrete chorus type emissions are generated in the equatorial region (L approximately 1.2) during cyclotron resonance interaction between the propagating whistler wave and the gyrating electrons. The whistler precursors are explained in terms of the mechanism suggested by Dowden (1972) }, keywords={ atmospheric radiation atmospherics magnetospheric electromagnetic wave propagation whistlers India AD 1972 03 VLF magnetospheric processes whistler precursors low latitude ground station Gulmarg March 1972 discrete chorus type emissions equatorial region cyclotron resonance interaction propagating whistler wave gyrating electrons }, mynotes={UNREAD}, }, @ARTICLE{SinghOct93, author={Singh, R.P. and Singh, A.K. and Singh, R.N.}, title={ Study of field-aligned irregularities by VLF whistlers and VHF scintillations }, journal={Indian Journal of Radio & Space Physics}, volume={22}, number={5}, year={1993}, month={Oct}, pages={342-6}, abstract={ Whistler wave ducting and VHF wave scintillations are known to be due to the plasma irregularities in the ambient medium. Whistler waves of natural origin and amplitude scintillations of FLEETSAT geostationary satellite signals have been simultaneously recorded at Varanasi, to study the morphology of irregularities present in the ionosphere. The preliminary results of these investigations are presented. It has been found that there is no positive correlation between whistler occurrence and VHF scintillations }, keywords={ atmospheric ionisation atmospheric structure ionosphere ionospheric electromagnetic wave propagation magnetosphere magnetospheric electromagnetic wave propagation plasma scintillation whistlers ionosphere EM wave propagation AD 1991 01 to 1992 06 magnetosphere EM wave propagation India whistler wave ducting ionosphere structure low-latitude ionosphere aeronomy field-aligned irregularities VLF whistlers VHF wave scintillations plasma irregularities amplitude scintillations FLEETSAT geostationary satellite signals Varanasi whistler occurrence 244.168 MHz 0 to 8 kHz }, mynotes={UNREAD}, }, @ARTICLE{SinghJun93, title={ Whistler studies at low latitudes: a review }, journal={Indian Journal of Radio & Space Physics}, volume={22}, number={3}, year={1993}, month={Jun}, pages={139-55}, abstract={ The information derived from whistler studies at low latitude Indian, Chinese and Japanese stations is reviewed. The enhanced occurrence rate during geomagnetic storm periods at low latitudes has been interpreted in terms of formation of additional ducts which at low latitudes have a lifetime of less than an hour and during magnetic storm period they are frequently formed and destroyed. Dispersion analysis yields electron density and large scale electric field distribution in the inner plasmasphere which is comparable to that derived from mid-latitude whistlers. The characteristic properties of low latitude whistlers are explained in terms of ducted and pro-longitudinal mode of propagation whereas equatorial whistlers follow field-aligned path in the inner plasmasphere and Earth-ionosphere waveguide mode for subionospheric path }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation reviews whistlers magnetosphere radiowave emission duct whistlers India China Japan propagation ionosphere whistler low latitude occurrence rate geomagnetic storm periods magnetic storm ducted pro-longitudinal mode plasmasphere Earth-ionosphere waveguide }, mynotes={UNREAD}, }, @ARTICLE{SinghMay96, author={Singh, U.P. and Narayan, D. and Singh, R.P. and Singh, R.N.}, title={ VLF emissions and determination of magnetospheric parameters }, journal={Adv. Space Res. (UK), Advances in Space Research}, volume={17}, number={10}, year={1996}, month={May}, pages={105-9}, abstract={ During routine observations of VLF whistlers, different types of VLF emissions such as chorus, risers, precursors etc. are observed during daytime at the low latitude ground station Gulmarg (geomag. lat. 24 degrees 10N and geomag. long. 174 degrees 24E). The generation mechanism of these emissions is considered to be a nonlinear cyclotron resonance interaction between whistler mode waves and energetic electrons. The limiting growth rate of the wave and the resonant energy of interacting electrons are evaluated. Considering the interaction region near the equatorial plane, different parameters like source height, interaction length, wave magnetic field and number of energetic electrons taking part in the generation of low latitude VLF emissions are determined. The results are discussed in the light of recorded features of whistlers and VLF emissions }, keywords={ cyclotron resonance electrons magnetospheric electromagnetic wave propagation radiowave propagation VLF emission magnetospheric parameters VLF whistlers daytime magnetosphere generation mechanism nonlinear cyclotron resonance whistler mode waves energetic electron interactions limiting growth rate source height interaction length wave magnetic field }, mynotes={UNREAD}, }, @ARTICLE{SkougOct96, author={Skoug, R.M. and Datta, S. and McCarthy, M.P. and Parks, G.K.}, title={ A cyclotron resonance model of VLF chorus emissions detected during electron microburst precipitation }, journal={Journal of Geophysical Research}, volume={101}, number={A10}, year={1996}, month={Oct}, pages={21481-91}, abstract={ VLF chorus, consisting of narrowband rising frequency emissions, has often been observed in association with microburst electron precipitation. The authors present the first simultaneous rocket observations of these two phenomena, with emphasis on understanding the source of the VLF emissions. The rocket experiment was launched on May 6, 1993, from Poker Flat, Alaska (L=5.6). The observed 1-4 kHz chorus emissions are interpreted in terms of a cyclotron resonance interaction. The frequency range of the risers and the observed electron energy range agree with those required for this interaction. Using a criterion derived from the conservation of energy during an interaction, it is shown that a cold plasma cyclotron resonance interaction can produce the lower-frequency portions of the observed chorus risers, from À1000 Hz to À2500 Hz, while a warm plasma model is required to produce frequencies >2500 Hz. The warm plasma model assumes a two-component plasma, with an isotropic cold component and a bi-Maxwellian warm component. The effect of the warm component is to change the wave dispersion relation, allowing the production of the higher-frequency risers. A portion of the anisotropy required to produce the high-frequency emissions can also be provided by a loss cone distribution. The chorus source is estimated from this cyclotron resonance theory to be located near the equatorial plane }, keywords={ atmospheric electron precipitation atmospherics cyclotron resonance VLF chorus emissions cyclotron resonance model electron microburst precipitation narrowband rising frequency emissions microburst electron precipitation rocket observations AD 1993 05 06 magnetosphere cold plasma cyclotron resonance interaction warm plasma model wave dispersion relation loss cone distribution 1 to 4 kHz }, mynotes={UNREAD}, }, @ARTICLE{SmithJan91, author={Smith, A.J. and Carpenter, D.L. and Corcuff, Y. and Rash, J.P.S. and Bering, E.A.}, title={ The longitudinal dependence of whistler and chorus characteristics observed on the ground near L=4 }, journal={Journal of Geophysical Research}, volume={96}, number={A1}, year={1991}, month={Jan}, pages={275-84}, abstract={ Discusses the similarities and differences in ELF and VLF whistler mode waves-chorus, hiss, and whistlers-received at four L approximately=4 Antarctic ground stations from a 2-day period in June 1982. Siple, Halley, and Sanae form a closely spaced ( approximately 20 degrees -0 degrees geomagnetic longitude) triplet, while Kerguelen is approximately 120 degrees (geomagnetic) to the east, on the opposite side of the South Atlantic geomagnetic anomaly }, keywords={ whistlers AD 1982 06 28 to 29 South Atlantic geomagnetic anomaly longitudinal dependence chorus characteristics ELF VLF whistler mode waves hiss whistlers Antarctic ground stations June 1982 Siple Halley Sanae Kerguelen }, mynotes={UNREAD}, }, @ARTICLE{SmithNov96, author={Smith, A.J. and Freeman, M.P. and Reeves, G.D.}, title={ Postmidnight VLF chorus events: a substorm signature observed at the ground near L=4 }, journal={Journal of Geophysical Research}, volume={101}, number={A11}, year={1996}, month={Nov}, pages={24641-53}, abstract={ Clouds of energetic electrons, injected sporadically into the nightside magnetosphere during substorm expansion phase onsets, can generate VLF whistler mode noise through the gyroresonance instability, which may then be observed on the ground or in space. Although these substorm-related chorus events (SCEs) have been reported occasionally in the literature, there seems to have been no systematic study, probably because of the lack, until now, of a well-adapted experimental technique. The VLF/ELF Logger Experiment (VELOX) instrument, located at Halley, Antarctica (76 degrees S, 26 degrees W, L=4.3), is, however, particularly well suited to a systematic study of this aspect of the substorm phenomenon. The data exist almost continuously from January 1992 onward, at 1-s time resolution in eight quasi-logarithmically spaced frequency bands covering the range 0.25-10 kHz. For this paper, 327 days of continuous data from 1992 have been analyzed. The 243 SCEs identified were observed on about 50% of days, almost exclusively in the 2300-0600 MLT local time range, and were characterized by limited duration (typically, À10 min at 1.5 kHz) and upward frequency drift of a band of usually weak and relatively unstructured chorus at a rate of À200 Hz min/sup -1/ between 0.5 and 5 kHz (corresponding to parallel electron energies in the range À10-100 keV). This drift is consistent with the combined eastward and inward motion of the resonant electrons due to azimuthal gradient-curvature drift and radial E*B drift under the action of substorm-enhanced westward electric fields of order 1 mV m/sup -1/ near the equatorial plane. The limited MLT viewing window of the station implies an overall detection efficiency for SCEs of À20%. The inferred annual mean substorm rate 1366+or-188 year/sup -1/, and inter substorm interval, 5.5+or-0.8 hours, are similar to the values derived using other techniques. However, the distribution of intervals between successive SCEs is different from that for su }, keywords={ atmospheric radiation magnetic storms magnetosphere whistlers magnetosphere radiowave emission postmidnight VLF chorus event substorm signature magnetic storm substorm expansion phase onset VLF whistler mode noise gyroresonance instability substorm-related chorus event AD 1992 AD 1993 AD 1994 AD 1995 ELF unstructured chorus 0.25 to 10 kHz }, mynotes={UNREAD}, }, @ARTICLE{SmithMay96, title={ Aspects of wave-particle interactions at mid-latitudes }, journal={Adv. Space Res. (UK), Advances in Space Research}, volume={17}, number={10}, year={1996}, month={May}, pages={213-22}, abstract={ Lightning-generated whistlers may be equally important as a loss process. Such lightning-induced electron precipitation (LEP) and its ionospheric signature is the subject of this paper. Although LEP may be detected and studied by a variety of ground-based, balloon-borne and satellite-borne sensors, through optical emissions, X-ray production, enhanced conductivity, or the direct measurement of the precipitating particles themselves, a technique using ground-based narrow-band VLF receivers to measure the Trimpi effect (the transient perturbations in amplitude and/or phase of received narrow-band VLF transmissions) caused by LEP-associated ionisation enhancements has become increasingly popular due to its simple instrumentation and wide field of view. Most work has concentrated on the 2100 dB is large enough to account for the observed wave intensity ( approximately 1 pT/sup 2/ Hz/sup -1/) in a single transit of the wave through the equatorial region ( lambda /sub m/or approximately=60 degrees ) the corresponding differences in the growth and damping rates are relatively small. For both the generalized Lorentzian and Maxwellian distributions, maximum wave growth due to hot proton temperature anisotropy occurs for parallel propagation, but significant wave growth can occur for wave normal angles ¹ psi ¹or=4.0 for the winter night model and at L>or=1.5 for the summer day model of the magnetosphere. All analyzed troughs are modelled with the same electron density depression of 15% and with the effective width of 215 km in the equatorial plane. Initial latitude ranges for various wave normal directions, from which rays are successfully guided, are moved equatorward from the trough centre. For one trough the initial latitude ranges are defined so that corresponding rays reach 300 km altitude in the conjugate hemisphere with a final wave normal angle inside the ionospheric transmission cone. The guidance of VLF waves by a trough is possible in a para-longitudinal mode or a gradient trapping mode, depending on initial positions. Changing these positions, there is a continuous transition from one ray path to the other. The main difference in the characteristics of rays guided in a para-longitudinal mode and a gradient trapping mode is the behaviour of the wave normal angle to the geomagnetic field. A para-longitudinal mode has lower value of this parameter than a gradient trapping mode. A ray guided in a gradient trapping mode deeply enters a trough. A slight difference of latitudinal gradients of the geomagnetic field and electron density in the lower altitude magnetosphere is is responsible for determining a type of mode for guiding whistlers by a trough. These whistlers are characterized by an upper cut-off frequency which is almost 0.5 f/sub Bmin/ }, keywords={ magnetospheric electromagnetic wave propagation whistlers radiowave propagation EM wave ray tracing whistler field-aligned depression guided electron density magnetosphere VLF wave trough centre conjugate hemisphere interhemispheric propagation ionospheric transmission cone }, mynotes={UNREAD}, }, @ARTICLE{Takahashi93, author={Takahashi, O. and Ohta, K. and Hayakawa, M.}, title={ On the structure of ducts for mid-latitude whistlers and their ionospheric transmission as deduced from the ground-based direction finding }, journal={Pure and Applied Geophysics}, volume={140}, number={3}, year={1993}, month={}, pages={519-35}, abstract={ The ground-based direction finding carried out at Ceduna, Australia (L=1.93) has yielded the structure for mid-latitude whistlers and their duct ionospheric transmission mechanism. It is found that the ducts tend to take place (or be formed) at the same latitudes and that such sheet-shaped ducts includes some inhomogeneities within them which act as field-aligned ducts }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation whistlers middle latitude whistler duct structure ionosphere radiowave propagation magnetosphere mid-latitude whistlers transmission ground-based direction finding Ceduna Australia mechanism sheet-shaped ducts }, mynotes={UNREAD}, }, @ARTICLE{TakahashiDec91, author={Takahashi, O. and Ota, K. and Baba, K. and Eguchi, H. and Hayakawa, M.}, title={ Ionospheric exit points of whistlers at high latitude }, journal={Memoirs of College of Engineering, Chubu University}, volume={27}, number={}, year={1991}, month={Dec}, pages={49-59}, abstract={ The presence of field-aligned ducts of whistlers observed on the ground is of essential importance, not only for middle latitudes but also for low latitudes. However, the characteristics of those whistler ducts such as their extent and separation are poorly understood. In order to study the ionospheric exit points of whistlers multipath whistlers observed at Ceduna (geomagnetic latitude 41.9 degrees ) in Australia were analysed. A digital processing technique and a FFT method were used for direction finding by the field analysis method. The radius of the duct at 100 km height, the extent of ionospheric exit points of whistlers observed at Ceduna is about 100 km. The distance interval between the exit points is about 500 km. The main lobe of the incident angle is never larger than 40 degrees observed }, keywords={ atmospheric structure guided electromagnetic wave propagation ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation whistlers high-latitude whistlers magnetosphere ducts VLF field-aligned whistler ducts ULF ducts radii whistlers directions AD 1989 08 11 ionosphere D-region lower ionosphere exit points spatial separation incident angle main lobe width fast Fourier transform method ionospheric exit points multipath whistlers Ceduna geomagnetic latitude 41.9 degrees Australia digital processing technique FFT method field analysis method distance interval 1 to 7 kHz 100 km 500 km }, mynotes={UNREAD}, }, @ARTICLE{TarcsaiApr89, author={Tarcsai, G. and Strangeways, H.J. and Rycroft, M.J.}, title={ Error sources and travel time residuals in plasmaspheric whistler interpretation }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={51}, number={4}, year={1989}, month={Apr}, pages={249-58}, abstract={ In the interpretation of observed whistlers by curve fitting, systematic travel time residuals appeared which were studied by extensive simulations using ray-tracing, numerical integration and curve fitting. The residuals were found to originate from the commonly used approximations in the refractive index and ray path of whistler mode waves, which result in travel time increments or decrements, not accounted for in whistler interpretation. These approximations and the assumed form of the electron density distribution also lead to systematic errors in the diagnostics of plasmaspheric electron density by whistlers. In addition, the effects of other error sources, including random measurement errors, are also reviewed briefly }, keywords={ magnetospheric electromagnetic wave propagation whistlers magnetosphere duct radiowave propagation VLF ELF travel time residuals plasmaspheric whistler interpretation curve fitting curve fitting ray path whistler mode waves 1 to 16 kHz }, mynotes={UNREAD}, }, @ARTICLE{ThejappaDec95, author={Thejappa, G. and Wentzel, D.G. and MacDowall, R.J. and Stone, R.G.}, title={ Unusual wave phenomena near interplanetary shocks at high latitudes }, journal={Geophysical Research Letters}, volume={22}, number={23}, year={1995}, month={Dec}, pages={3421-4}, abstract={ Reports on several interplanetary shocks that are unusual because waves at about 10 Hz are highly electrostatic in the upstream region yet highly electromagnetic in the downstream region. These shocks, detected by the Unified Radio and Plasma Wave Experiment (URAP) on Ulysses are supercritical reverse shocks, which occurred predominantly at high heliographic latitudes. The level of wave activity is observed to be independent of the angle between the magnetic field and the shock normal, the Mach number, and the change in the ratio of ion thermal pressure to magnetic pressure from upstream to downstream regions. Since the energy in the upstream electrostatic waves is small compared to the downstream electromagnetic waves, mode conversion from electrostatic to electromagnetic at the shock is not a viable mechanism. The upstream and downstream waves are likely to be generated by separate mechanisms, with lower hybrid waves being the most probable candidates for the upstream waves and electromagnetic lower hybrid or whistlers for the downstream waves }, keywords={ plasma hybrid waves solar wind whistlers unusual wave phenomena interplanetary shocks high latitudes electrostatic waves upstream region downstream region Unified Radio and Plasma Wave Experiment URAP Ulysses supercritical reverse shocks wave activity shock normal Mach number ion thermal pressure magnetic pressure upstream electrostatic waves downstream electromagnetic waves mode conversion lower hybrid waves whistlers 10 Hz }, mynotes={UNREAD}, }, @ARTICLE{ThomasJun83, title={ Electron pitch-angle scattering by low frequency waves at the geomagnetic equator }, journal={Nature}, volume={303}, number={5920}, year={1983}, month={Jun}, pages={785-7}, abstract={ Satellite observations have revealed details on the strength of the pulsing extremely low frequency (ELF) hiss in the equatorial region which maps down to the auroral zone. It is shown to be insufficient to produce pitch-angle scattering of energetic electrons into the loss cone at a sufficiently high rate to explain the characteristics of the measured pitch-angle distributions in pulsating auroras, within the framework of the theory proposed by Coroniti and Kennel (1970). It is suggested that wave-particle interactions involving both broadband incoherent ELF waves and narrow band coherent very low frequency (VLF) waves may be able to produce a sufficiently high rate of pitch-angle scattering }, keywords={ atmospheric electron precipitation atmospherics aurora ionosphere magnetosphere pulsing ELF hiss narrowband coherent VLF waves low frequency waves geomagnetic equator equatorial region auroral zone pitch-angle scattering energetic electrons loss cone pulsating auroras wave-particle interactions broadband incoherent ELF waves }, mynotes={UNREAD}, }, @ARTICLE{ThorneMar96, author={Thorne, R.M. and Horne, R.B.}, title={ Whistler absorption and electron heating near the plasmapause }, journal={Journal of Geophysical Research}, volume={101}, number={A3}, year={1996}, month={Mar}, pages={4917-28}, abstract={ Using the HOTRAY code, the authors demonstrate that lightning-generated whistlers which enter the magnetosphere over a broad range of latitudes ( Delta lambda approximately=5 degrees ) just inside the plasmapause are strongly focused by the steep plasma density gradient into a narrow range of L shells near the equatorial region. The wave normal angle also remains closely aligned (+or-20 degrees ) with the magnetic field direction along the entire ray path. Under such conditions, Landau resonance is relatively unimportant, and the wave amplitude is controlled by cyclotron resonant interactions with energetic electrons. All waves with frequencies comparable to or larger than one third of the equatorial electron gyrofrequency can be strongly absorbed by resonant electrons, leading to electron heating perpendicular to the ambient magnetic field at energies above 100 eV. Consequently, in the presence of this strongly focused source of wave energy, the electron distribution should evolve toward a marginally stable anisotropic equilibrium distribution with T/sub perpendicular to />T/sub ¹¹/. In order to simulate this perpendicular heating, they allow the anisotropy of the electron distribution to evolve so that damping is minimized at a frequency of 5 kHz, corresponding to the peak in the power spectrum of spherics above the ionosphere. When the plasmapause is located at L/sub p/=4.5, whistlers above 4 kHz experience more than 20 dB attenuation owing mainly to cyclotron resonance with 0.1 to 1 keV electrons near the equator. It is unlikely that these waves would be detectable on the ground. This attenuation will produce an upper cutoff in the whistler frequency considerably below one half the equatorial electron gyrofrequency for waves that are guided along the plasmapause. In contrast, lower-frequency whistlers (f approximately=1-3 kHz) should be amplified by the anisotropic electron population; such waves are able to propagate to the conjugate ionosphere and thus be dete }, keywords={ magnetospheric electromagnetic wave propagation whistlers EM wave plasma wave magnetosphere whistler absorption radiowave propagation electron heating plasmapause plasmasphere HOTRAY code lightning-generated whistlers strongly focused steep plasma density gradient equatorial region wave amplitude cyclotron resonant interaction energetic electrons damping }, mynotes={UNREAD}, }, @ARTICLE{ThorneNov70, author={Thorne, R.M. and Burton, R.K. and Holzer, R.E. and Smith, E.J.}, title={ A study of plasmaspheric hiss }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={51}, number={11}, year={1970}, month={Nov}, pages={803}, abstract={ The flux of energetic electrons trapped inside the plasmasphere appears to be controlled by plasma wave turbulence associated with the cyclotron instability. On almost every passage of OGO-5 through the plasmasphere, ELF hiss in the range between 1-1000 Hz has been detected by the triaxial search coil magnetometer. A statistical description of the spatial distribution, polarization, peak power spectral density and frequency structure of the signals has been obtained. The hiss shows no definite polarization but is banded in frequency. Correlations have been made with geomagnetic indices and simultaneous measurements of energetic electrons. Computer analysis of the triaxial hiss waveforms yields their direction of propagation. The accessibility of the waves to different regions of the magnetosphere has been studied with a view to locating their source region }, keywords={ atmospheric electromagnetic wave propagation atmospherics magnetosphere plasmasphere hiss magnetosphere cyclotron instability energetic electrons }, mynotes={UNREAD}, }, @ARTICLE{ThorneApr72, title={ Wave-particle interactions at the plasmapause }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={53}, number={4}, year={1972}, month={Apr}, pages={489}, abstract={ There is considerable evidence to suggest that the pronounced drop in thermal plasma density at the plasmapause strongly influences the stability and resulting flux levels of energetic radiation belt particles. Electromagnetic instabilities typically require a threshold energy comparable to B/sup 2//8 pi N; the magnetic energy per particle. The low plasma densities found exterior to the plasmapause provide a region of stability for ring current particles with energy less than 100 KeV. However, these particles which contain the bulk energy density in the radiation belts become strongly unstable just within the high density plasmasphere. Intense ion-cyclotron turbulence generated by ring current protons can account for the precipitational removal of such protons, the excitation of SAR arcs, and the parasitic pitch-angle scattering loss of energetic protons and relativistic electrons within a narrow region just inside the plasmapause. A similar instability of low energy electrons could be the generation mechanism of the ELF whistler-mode hiss observed throughout the plasmasphere }, keywords={ magnetosphere plasma stability plasmapause thermal plasma density stability flux levels energetic radiation belt particles electromagnetic instabilities ring current particles bulk energy density excitation of SAR arcs wave particle interactions ion cyclotron turbulence pitch angle scattering loss ELF whistler mode hiss }, mynotes={UNREAD}, }, @ARTICLE{TixierMar84, author={Tixier, M. and Charcosset, G. and Corcuff, Y. and Okada, T.}, title={ Propagation modes of whistlers received broad satellites over Europe }, journal={Annales Geophysicae}, volume={2}, number={2}, year={1984}, month={Mar}, pages={211-20}, abstract={ A comparison between whistlers received simultaneously on the ground and on board satellites during a Franco-Japanese campaign organized in 1978 shows a clear latitudinal evolution of these phenomena over Europe, from L=1.7 to L=3.7. The aim of this paper is to discuss the theoretical explanation of the occurrence and characteristics of these whistlers in terms of different VLF propagation modes inside the magnetosphere }, keywords={ magnetospheric electromagnetic wave propagation radiowave propagation whistlers EM wave propagation radiowave AD 1978 12 to 1979 01 whistlers Europe latitudinal evolution VLF propagation modes magnetosphere }, mynotes={UNREAD}, }, @ARTICLE{TokarJan85, author={Tokar, R.L. and Gurnett, D.A.}, title={ The propagation and growth of whistler mode waves generated by electron beams in Earth's bow shock }, journal={J. Geophys. Res. (USA), Journal of Geophysical Research}, volume={90}, number={A1}, year={1985}, month={Jan}, pages={105-14}, abstract={ The propagation and growth of whistler mode waves generated by electron beams within the Earth's bow shock are investigated using a planar model for the bow shock and a model electron distribution function. Within the shock, the model electron distribution function possesses a field-aligned T/sub perpendicular to />T/sub /// beam that is directed toward the magnetosheath. Waves with frequencies between about 30 and 150 Hz with a wide range of wave normal angles are generated by the beam via the normal cyclotron resonance. The ray paths for most of these waves are directed toward the solar wind. These wave packets grow to large amplitudes, because they spend a long time in the growth region. The results suggest that whistler mode noise within the shock should increase in amplitude with increasing upstream theta /sub Bn/. The study provides an explanation for the origin of much of the whistler mode turbulence observed at the bow shock }, keywords={ electromagnetic wave propagation interplanetary matter magnetosphere plasma shock waves solar wind whistlers solar wind-magnetosphere interaction interplanetary medium wave-particle interactions whistler waves generation whistler waves propagation whistler amplitudes growth field-aligned electron beams planar bow shock model cyclotron resonance whistler waves Hz 0030 to 0150 upstream shock normal angle large-amplitude whistler wave packets whistler mode waves Earth's bow shock model electron distribution function magnetosheath wave normal angles ray paths growth region whistler mode noise whistler mode turbulence }, mynotes={UNREAD}, }, @ARTICLE{TorkarOct87, author={Torkar, K.M. and Riedler, W. and Kremser, G. and Korth, A. and Ullaland, S. and Stadsnes, J. and Block, L.P. and Iversen, I.B. and Tanskanen, P. and Kangas, J. and Cornilleau-wehrilin, N. and Solomon, J.}, title={ A study of the interaction of VLF waves with equatorial electrons and its relationship to auroral X-rays in the morning sector }, journal={Planetary and Space Science}, volume={35}, number={10}, year={1987}, month={Oct}, pages={1231-53}, abstract={ Precipitation of electrons in the morning sector of the auroral zone related to magnetospheric substorm activity has been observed via X-ray measurements from balloons. Coordinated observations within the IMS period both aboard balloons and on the geostationary satellite GEOS-2 provided detailed information for the study of the relation between the distribution function of energetic electrons at GEOS-2 and the precipitation at and near the magnetically conjugate point in the auroral zone. The anisotropy of the electron distribution function is determined by the injection processes and by further modifications, e.g. convection and drift. It is large enough to allow the growth of VLF wave responsible for scattering of electrons into the loss cone }, keywords={ atmospheric electron precipitation atmospheric radiation atmospherics aurora ionosphere magnetic storms magnetosphere radiation belts auroral electron precipitation auroral ionosphere electron distribution function anisotropy electron drift magnetosphere convection AD 1978 to 1979 magnetic storms wave growth rates geosynchronous orbit VLF waves equatorial electrons auroral X-rays morning sector magnetospheric substorm activity balloons IMS period geostationary satellite GEOS-2 energetic electrons magnetically conjugate point auroral zone injection processes loss cone 6.6 Earthradii }, mynotes={UNREAD}, }, @ARTICLE{Torres-SilvaDec96, author={Torres-Silva, H. and Reggiani, N. and Sakanaka, P.H.}, title={ The effect of chirality on a plasma medium }, journal={Revista Mexicana de Fisica}, volume={42}, number={6}, year={1996}, month={Dec}, pages={989-1000}, abstract={ The theoretical properties of a composite chiral-plasma medium are developed. By using the reaction theorem, for a magnetized chiroplasma, we obtain the proof of nonreciprocity based upon the constitutive relationships between electromagnetic vectors E, B, H, D. Using the Maxwell's equations and the proposed constitutive relations for a chiral-plasma medium, we derive the vector E and H equations and from these equations, dispersion relations and E-field polarization are obtained. For circularly polarized waves, a new mode conversion is founded due to the chiral effect. For the lower branch of the extraordinary wave mode there is no more bands of forbidden frequencies and the reflection point vanishes when the chiral parameter increases }, keywords={ chirality dispersion relations plasma theory plasma waves chirality chiral parameter composite chiral-plasma medium reaction theorem magnetized chiroplasma nonreciprocity constitutive relationships electromagnetic vectors Maxwell's equations reflection point forbidden frequencies dispersion relations E-field polarization H equations circularly polarized waves mode conversion extraordinary wave mode lower branch vector Helmholtz equation high frequency waves }, mynotes={UNREAD}, }, @ARTICLE{TreumannOct96, author={Treumann, R.A. and Dubouloz, N. and Pottelette, R.}, title={ Electron acceleration from localized lower-hybrid waves }, journal={Adv. Space Res. (UK), Advances in Space Research}, volume={18}, number={8}, year={1996}, month={Oct}, pages={291-4}, abstract={ Stochastic acceleration of electrons in lower hybrid wave cavitons is investigated for packets assumed to contain a broad spectrum of short wavelength oscillations. Such cavitons accelerate electrons to moderate energies producing nonsymmetric, flat-top, and beamlike distribution functions }, keywords={ electrons magnetosphere plasma hybrid waves magnetosphere electron lower hybrid waves wave packets distribution functions cavitons diffusion coefficient stochastic acceleration velocity distribution }, mynotes={UNREAD}, }, @ARTICLE{TsurutaniFeb81, author={Tsurutani, B.T. and Smith, E.J. and Thorne, R.M. and Anderson, R.R. and Gurnett, D.A. and Parks, G.K. and Lin, C.S. and Russell, C.T.}, title={ Wave-particle interactions at the magnetopause: contributions to the dayside aurora }, journal={Geophysical Research Letters}, volume={8}, number={2}, year={1981}, month={Feb}, pages={183-6}, abstract={ A strong correlation between intense, broad-band 10-10/sup 5/ Hz plasma waves and 1-6 keV electrons and protons are observed on ISEE 1 and 2 at the low latitude dayside magnetopause. Wave and particle features have been characterized by taking averages over ten events. The 10-10/sup 3/ Hz magnetic waves and the 10-10/sup 5/Hz electric emissions can be represented by the power-law spectra, I/sub m/=10 f/sup -3.9/ nT/sup 2//Hz and I/sub e/=3*10/sup -5/ f/sup -2.8/ V/sup 2//m/sup 2/ Hz, respectively. The electron and proton fluxes and spectral shapes are nearly constant from event-to-event. Using typical magnetopause plasma and field values of 20 cm/sup -3/ and 50 nT, it is shown that the 1-10 keV electrons and protons are scattered near the limit of strong pitch angle diffusion by the observed waves. A precipitation flux of approximately 0.15 ergs/cm/sup 2/ sec is calculated, indicating a significant contribution to the dayside aurora }, keywords={ atmospheric electron precipitation atmospheric proton precipitation aurora magnetosphere magnetopause dayside aurora plasma waves electrons protons low latitude pitch angle diffusion precipitation magnetosphere wave particle interaction ionosphere }, mynotes={UNREAD}, }, @ARTICLE{UngstrupMay90, author={Ungstrup, E. and Bahnsen, A. and Wong, H.K. and Andre, M. and Matson, L.}, title={ Energy source and generation mechanism for auroral kilometric radiation }, journal={Journal of Geophysical Research}, volume={95}, number={A5}, year={1990}, month={May}, pages={5973-81, 6113-14}, abstract={ The orbit of the Swedish satellite Viking was optimized for observations of plasma phenomena in the auroral acceleration regions, including auroral kilometric radiation. The auroral kilometric radiation (AKR) is the strongest electromagnetic radiation produced on auroral field lines, and the Viking satellite passed through the source region of this radiation on many orbits, as evidenced by the very strong signals observed at the electron cyclotron frequency. For the first time, electron distribution functions were observed inside the AKR source region and immediately adjacent to the source region. The particle data show the presence of energetic electrons in and around the source region and also of upgoing ion beams of several keV energy in and only in the source region. Thus the particle data show clear signatures of parallel electric potentials both above and below the AKR source. The authors observations are in agreement with the cyclotron maser instability theory including the effect of a parallel electric field }, keywords={ atmospheric radiation magnetosphere radiowave emission AKR energy source AD 1986 LF magnetosphere plasma instability generation mechanism auroral kilometric radiation electromagnetic radiation source region electron distribution functions energetic electrons upgoing ion beams parallel electric potentials cyclotron maser instability theory }, mynotes={UNREAD}, }, @ARTICLE{VampolaMar88, author={Vampola, A.L. and Adams, C.D.}, title={ Outer zone electron precipitation, produced by a VLF transmitter }, journal={Journal of Geophysical Research}, volume={93}, number={A3}, year={1988}, month={Mar}, pages={1849-58}, abstract={ By means of high-resolution pitch angle measurements made by a magnetic-focusing electron spectrometer on the S3-3 satellite while in the drift loss cone region of the magnetosphere, characteristics of fluxes of 108- to 654-keV electrons precipitated in the inner zone, in the slot region, and in the outer zone of the magnetosphere are all shown to be consistent with the precipitation's having been produced by the same ground-based VLF transmitter, UMS. Pitch angle measurements are used to locate the longitude of precipitation. The temporal pattern of transmitter operation obtained from synoptic data from a ground-based VLF receiver is used along with drift rate calculations to predict the electron energies as a function of L shell which should be observable by the S3-3 instrument. The study indicates that ground-based VLF transmitters, are instrumental in precipitating electrons in the outer zone }, keywords={ atmospheric electron precipitation atmospherics magnetosphere magnetospheric electromagnetic wave propagation radiation belts magnetosphere outer zone UMS transmitter precipitating electron fluxes AD 1976 07 28 magnetosphere L-shell radius electron precipitation high-resolution pitch angle measurements magnetic-focusing electron spectrometer S3-3 satellite drift loss cone region inner zone slot region ground-based VLF transmitter temporal pattern transmitter operation synoptic data ground-based VLF receiver drift rate calculations electron energies 1.50 to 6.50 Earthradii 108 to 654 keV }, mynotes={UNREAD}, }, @ARTICLE{VeltriAug93, author={Veltri, P. and Zimbardo, G.}, title={ Electron - whistler interaction at the Earth's bow shock. 1. Whistler instability }, journal={Journal of Geophysical Research}, volume={98}, number={A8}, year={1993}, month={Aug}, pages={13325-33}, abstract={ The interaction of whistler waves with the electrons in the Earth's quasi-perpendicular bow shock of November 7, 1977, is considered. A Monte Carlo simulation which includes the effect of electrostatic noise is used to obtain the electron distribution function f/sub e/ across the shock layer. The simulated f/sub e/ is rather anisotropic and in the shock foot has a marked loss cone structure which is evident in the data. The authors study the instability of f/sub e/ with respect to the emission of whistler modes. Strong whistler emission from the electrons is found, with frequency and spatial dependencies of the growth rate in good agreement with the observed magnetic noise. Most of the whistlers are generated in the shock foot, where the loss cone in the electron distribution function is found. This indicates that in quasi-perpendicular collisionless shock, besides the reflected ion beam and the field-aligned electron beam, an important source of whistler mode waves is the electron loss cone due to reflection from the magnetic ramp }, keywords={ magnetosphere plasma instability whistlers bow shock whistler wave quasi-perpendicular Monte Carlo electrostatic noise electron distribution function growth rate collisionless shock magnetosphere plasma wave wave particle interaction plasma instability model }, mynotes={UNREAD}, }, @ARTICLE{VillalonOct95, author={Villalon, E. and Burke, W.J.}, title={ Pitch angle scattering of diffuse auroral electrons by whistler mode waves }, journal={Journal of Geophysical Research}, volume={100}, number={A10}, year={1995}, month={Oct}, pages={19361-9}, abstract={ Resonant electron-whistler interactions in the plasma sheet are investigated as possible explanations of the nearly isotropic fluxes of low-energy electrons observed above the diffuse aurora. Whistler mode waves, propagating near the resonance cone with frequencies near or larger than half the equatorial electron cyclotron frequency, can interact with low-energy plasma sheet electrons. A Hamiltonian formulation is developed for test particles interacting with the coherent chorus emission spectra. The authors consider the second-order resonance condition which requires that inhomogeneities in the Earth's magnetic field be compensated by a finite bandwidth of wave frequencies to maintain resonance for extended distances along field lines. These second-order interactions are very efficient in scattering the electrons toward the atmospheric loss cone. Numerical calculations are presented for the magnetic shell L=5.5 for wave amplitudes of approximately 10/sup -6/ V/m, using different frequency and magnetospheric conditions }, keywords={ ionosphere magnetosphere radiation belts whistlers magnetosphere trapped particle, plasmasphere radiation belt plasma sheet pitch angle scattering diffuse auroral electrons whistler mode wave plasma wave wave particle interaction resonant electron whistler interaction isotropic flux low-energy electron diffuse aurora resonance cone Hamiltonian formulation equatorial electron cyclotron frequency coherent chorus emission spectra second-order resonance condition inhomogeneities second-order interactions numerical calculation ionosphere }, mynotes={UNREAD}, }, @ARTICLE{VillalonJun91, author={Villalon, E. and Burke, W.J.}, title={ Near-equatorial pitch angle diffusion of energetic electrons by oblique whistler waves }, journal={Journal of Geophysical Research}, volume={96}, number={A6}, year={1991}, month={Jun}, pages={9655-67}, abstract={ The pitch angle scattering of trapped, energetic electrons by obliquely propagating whistler waves in the equatorial regions of the plasmasphere is investigated. Storm-injected electrons moving along field lines near the equator interact with electromagnetic waves whose frequencies are Doppler-shifted to some harmonic of the cyclotron frequency. Relativistic, quasi-linear theory is applied to obtain self-consistent equations describing the temporal evolution of waves and particles over time scales which are longer than the particle bounce time and group time delay of the waves. The equilibrium solutions and their stability are studies, considering the reflection of the waves by the ionosphere and the coupling of multiple harmonic resonances. The contributions of nonlocal wave sources are also included in the theory }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation plasma radiation belts whistlers magnetosphere radiation belt pitch angle diffusion energetic electrons oblique whistler waves equatorial regions plasmasphere cyclotron frequency quasi-linear theory self-consistent equations temporal evolution reflection ionosphere multiple harmonic resonances nonlocal wave sources }, mynotes={UNREAD}, }, @ARTICLE{VillalonNov89, author={Villalon, E. and Burke, W.J. and Rothwell, P.L. and Silevitch, M.B.}, title={ Quasi-linear wave-particle interactions in the Earth's radiation belts }, journal={Journal of Geophysical Research}, volume={94}, number={A11}, year={1989}, month={Nov}, pages={15243-56}, abstract={ Studies the gyroresonant interactions of energetic trapped electrons and protons in the Earth's radiation zones with ducted electromagnetic cyclotron waves. A set of equations is derived based on the Fokker-Planck theory of pitch angle diffusion. They describe the evolution in time of the number of particles in the flux tube and the energy density of waves, for the interaction of Alfven waves with protons and of whistler waves with electrons. The equilibrium solutions for particle fluxes and wave amplitudes are stable under small local perturbations. The reflection of the waves in the ionosphere is discussed. To efficiently dump the energetic particles from the radiation belts, the reflection coefficient must be very close to unity so that the wave amplitudes can grow to high values. The stability analysis around the equilibrium solutions for precipitating particle fluxes and wave intensity show that an actively excited ionosphere can cause the development of explosive instabilities }, keywords={ atmospheric electron precipitation atmospheric proton precipitation ionospheric electromagnetic wave propagation magnetohydrodynamic waves magnetosphere magnetospheric electromagnetic wave propagation radiation belts whistlers quasi-linear wave-particle interactions magnetosphere coherent VLF whistler-mode waves magnetosphere trapped protons cyclotron wave reflection particle numbers evolution energetic particles precipitation wave energy density evolution narrow-band MHD waves ionosphere EM wave propagation ionosphere height-integrated conductivity increase magnetic flux tube heating Earth's radiation belts gyroresonant interactions energetic trapped electrons ducted electromagnetic cyclotron waves Fokker-Planck theory pitch angle diffusion Alfven waves protons equilibrium solutions particle fluxes wave amplitudes small local perturbations reflection coefficient precipitating particle fluxes wave intensity actively excited ionosphere explosive instabilities }, mynotes={UNREAD}, }, @ARTICLE{VolkomirskayaDec88, author={Volkomirskaya, L.B. and Gorbunov, S.A. and Panfilov, S.V. and Reznikov, A.E.}, title={ Determination of wave characteristics of VLF-waves by means of multicomponent electromagnetic field measurements }, journal={Planetary and Space Science}, volume={36}, number={12}, year={1988}, month={Dec}, pages={1305-15}, abstract={ Multicomponent data of the electromagnetic field obtained on the Aureol-3 satellite were studied. On the basis of the application of multispectral analysis, nonlinear interactions on the harmonics of the proton gyro-frequency were determined. From the power spectra of the low frequency radiation components, the principal regulations of behaviour of the vectors of the wave normal and of the wave distribution function were found from the frequency and the invariant latitude L. It is noted, that at frequencies below the proton gyro-frequency there often arises a second maximum in the form of a wave distribution function, that can be interpreted as a reflected wave }, keywords={ atmospherics ionosphere magnetosphere magnetosphere ionosphere atmosphere atmospherics wave characteristics VLF-waves multicomponent electromagnetic field measurements Aureol-3 nonlinear interactions harmonics proton gyro-frequency power spectra wave normal wave distribution function reflected wave }, mynotes={UNREAD}, }, @ARTICLE{Voyevudskiy84, author={Voyevudskiy, V.P. and Lundin, B.V.}, title={ Determining the properties of the plasma and the VLF signal from the spectral matrix of the wave field detected in a region which is a source of magnetospheric noise }, journal={Geomagnetizm i Aeronomiya}, volume={24}, number={1}, year={1984}, month={}, pages={}, abstract={ The wave vector and the polarization vector of a narrow-band, plane-wave VLF signal received in a zone which is a source of magnetospheric noise can be determined from the magnetic part of the spectral matrix of the measured field. Expressions are given for determining certain properties of the magnetospheric plasma in the reception zone }, keywords={ atmospheric radiation atmospheric techniques atmospherics magnetosphere plasma space research magnetospheric noise source region VLF atmospherics plasma properties VLF signal properties matrix magnetic component atmospheric techniques space research narrow-band plane-wave VLF signal aeronomy spectral matrix wave field wave vector polarization vector magnetospheric plasma reception zone }, mynotes={UNREAD}, }, @ARTICLE{VyasJan75, author={Vyas, N.K. and Das, A.C.}, title={ Landau damping and cyclotron resonance in uniform magnetoplasma }, journal={Nature}, volume={253}, number={5486}, year={1975}, month={Jan}, pages={29-30}, abstract={ The formation of a ledge in the electron distribution functions during Landau damping produces steep gradients at the boundaries of the disturbed region of the distribution function. This makes the pitch angle distribution sufficiently anisotropic to amplify a gyroresonant whistler mode perturbation at the appropriate frequencies. The system under consideration consists of a homogeneous, collisionless hot plasma in a uniform magnetic field B/sub 0/, a spectrum of electron plasma waves with their propagation vectors k antiparallel to B/sub 0/, and a wide band whistler mode perturbation with k parallel to B/sub 0/ }, keywords={ plasma plasma waves whistlers Landau damping cyclotron resonance uniform magnetoplasma electron distribution functions pitch angle distribution gyroresonant whistler mode electron plasma waves }, mynotes={UNREAD}, }, @ARTICLE{Wagner83, author={Wagner, C.-U. and Lauter, E.A. and Grafe, A. and Nikutowski, B.}, title={ Precipitation of electrons from the electron radiation belt }, journal={Gerlands Beitraege zur Geophysik}, volume={92}, number={5}, year={1983}, month={}, pages={361-7}, abstract={ The precipitation of high-energy electrons from the radiation belt during the recovery phase of magnetospheric storms and the restoration of the slot region are discussed. A belt of increased ionization is produced by these precipitating high-energy electrons, leading to the well-known post-storm effect. The motion of the poleward boundary of this precipitation belt in dependence on storm time is concluded to reflect the motion of the plasmapause. Theoretical calculation of the pitch-angle diffusion coefficient leads to the conclusion that only a combined action of ELF and VLF hiss can result in sufficient pitch-angle diffusion }, keywords={ atmospheric electron precipitation atmospheric ionisation atmospheric radiation atmospherics ionosphere magnetic storms magnetosphere radiation belts plasmapause motion ionosphere magnetic storms ELF hiss AD 1972 08 02 to 17 AD 1970 03 electron radiation belt precipitation high-energy electrons recovery phase magnetospheric storms slot region increased ionization poleward boundary precipitation belt storm time pitch-angle diffusion coefficient VLF hiss }, mynotes={UNREAD}, }, @ARTICLE{WangMar70, author={Wang, T.N.C. and Bell, T.F.}, title={ On VLF radiation resistance of an electric dipole in a cold magnetoplasma }, journal={Radio Science}, volume={5}, number={3}, year={1970}, month={Mar}, pages={605-10}, abstract={ By using full-wave theory, an analysis is made of the radiation resistance of a short filamentary electric dipole, oriented with an arbitrary angle with respect to the static magnetic field, in a cold, uniform magnetoplasma. The frequency range considered lies below the local lower hybrid resonance frequency and above the proton gyrofrequency, and in this range approximate closed-form expressions for the radiation resistance are obtained by using a plasma model appropriate to the magnetosphere }, keywords={ antenna theory electromagnetic wave propagation in plasma plasma radiation resistance (electric) }, mynotes={UNREAD}, }, @ARTICLE{WashimiDec76, title={ Wave-trapping in an inhomogeneous magnetoplasma }, journal={Journal of the Physical Society of Japan}, volume={41}, number={6}, year={1976}, month={Dec}, pages={2098-105}, abstract={ The multi-dimensional wave equations for the waves propagating along a magnetic field in an inhomogeneous plasma are derived and the wave-trapping is discussed. It is shown that the wave equations are reduced to the Schrodinger-type ones in which the sign of the coefficient of the second derivative depends on ( psi / theta ) theta =0 where psi is the angle between the field line and the ray, and theta is the angle between the field line and the wave normal. The physical reason for the wave trapping is explained by comparing the sign of ( psi / theta ) theta =0 with that of the effective potential in the wave equation. As an example, wave trapping of the whistler wave in geo-magnetosphere is considered }, keywords={ electromagnetic wave propagation in plasma magnetospheric electromagnetic wave propagation whistlers inhomogeneous magnetoplasma whistler wave wave trapping Schrodinger type equations multidimensional wave equations magnetosphere }, mynotes={UNREAD}, }, @ARTICLE{WebbNov77, author={Webb, D.C. and Lanzerotti, L.J. and Park, C.G.}, title={ A comparison of ULF and VLF measurements of magnetospheric cold plasma densities }, journal={Journal of Geophysical Research}, volume={82}, number={32}, year={1977}, month={Nov}, pages={5063-72}, abstract={ Equatorial cold plasma density profiles determined from VLF whistlers propagating in magnetospheric ducts are compared with densities computed from the observations of ULF hydromagnetic waves (geomagnetic pulsations). The densities obtained by the ULF technique are based on the identification of resonant geomagnetic field lines, assumed to be driven by a monochromatic source. The ULF results thus obtained agree well with the whistler results throughout the period, June 17-20, 1973, when simultaneous data comparisons could be made. The ULF observations show that at mid-latitudes, shorter-period resonances can be supported in the plasma trough region, while those of longer period can occur inside the plasmasphere }, keywords={ atmospheric pressure and density atmospheric techniques magnetohydrodynamic waves magnetosphere magnetospheric electromagnetic wave propagation micropulsations whistlers magnetospheric cold plasma densities VLF whistlers magnetospheric ducts ULF hydromagnetic waves geomagnetic pulsations resonant geomagnetic field lines monochromatic source plasma trough region plasmasphere ULF MHD waves micropulsations 1973 June 17 to 20 equatorial plasma density profiles short period resonances long period resonances }, mynotes={UNREAD}, }, @ARTICLE{Xu-Wen-YaoSep89, title={ Effects of initial wave normal angle on propagation of non-ducted whistler wave at mid and low latitudes }, journal={Acta Geophysica Sinica}, volume={32}, number={5}, year={1989}, month={Sep}, pages={501-6}, abstract={ Propagation of non-ducted whistler wave at mid and low latitudes has been studied for different initial wave normal angle delta /sub s/ by means of the ray-tracing technique. The results show that in the case of delta s0 degrees , whistler rays will move inward, and converge to lower latitudes in another hemisphere and when delta /sub s/>10 degrees , this group of whistler waves has smaller dispersion. On the basis of the above-mentioned characteristics, a possible mechanism is proposed for explaining continuous variation of whistler dispersion }, keywords={ magnetospheric electromagnetic wave propagation whistlers middle latitude radiowave nonducted magnetosphere initial wave normal angle propagation whistler wave low latitudes ray-tracing dispersion }, mynotes={UNREAD}, }, @ARTICLE{WescottMay85, author={Wescott, E.M. and Stenbaek-Neilsen, W.C. and Hallinan, T. and Deehr, C. and Romick, J. and Olson, J. and Kelley, J.C. and Pfaff, R. and Torbert, R.B. and Newell, P. and Foppl, H. and Fedder, J. and Mitchell, H.}, title={ Plasma-depleted holes, waves, and energized particles from high-altitude explosive plasma perturbation experiments }, journal={Journal of Geophysical Research}, volume={90}, number={A5}, year={1985}, month={May}, pages={4281-98}, abstract={ High explosive shaped charge experiments King Crab and Bubble Machines I and II, designed to perturb the ambient plasma and magnetic field, were flown above 460 km on Taurus Tomahawk rockets from Poker Flat in March 1980, 1981, and 1982, respectively. The last flights were a mother-daughter combination with the instrumentation section remaining attached to the rocket. The first experiment, King Crab, revealed the existence of a barium plasma depleted region or dark hole of about 5 km diameter centered on the burst. For the Bubble Machine II experiment ground-based optical and telluric field instrumentation recorded evidence for injection-induced waves of about 5-s period. Delay times indicate a slow propagation from the burst point. Promptly following the release, auroral intensity ion beams were observed with energies up to 6.8 keV. Evidence suggests that these particles were not energized by the explosion but that they represent an existing ion conic population pitch angle scattered by the released barium into the view of the detector }, keywords={ F-region ionosphere explosion plasma depleted hole ionosphere plasma wave plasma depletion ion cloud Ba AD 1982 03 15 Bubble Machine AD 1980 03 16 F-region high-altitude explosive plasma perturbation experiments shaped charge King Crab dark hole }, mynotes={UNREAD}, }, @ARTICLE{WingleeJun85, title={ Enhanced growth of whistlers due to bunching of untrapped electrons }, journal={Journal of Geophysical Research}, volume={90}, number={A6}, year={1985}, month={Jun}, pages={5141-52}, abstract={ The theory presented complements Helliwell's (1967) phenomenological model for triggering of discrete VLF emissions by providing a mechanism which allows enhanced narrow-band wave growth due to phase bunching of electrons by the triggering wave. The essentially new feature is the relaxation of the time asymptotic assumption in evaluating the linear response of the plasma. This introduces a new phenomenon off-resonant bunching of electrons, which in the theory presented eventually gives rise to amplification and triggering. Although several aspects of the theory need to be examined in greater detail, this bunching mechanism seems likely as the basic mechanism for the amplification and triggering of discrete VLF emissions }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation whistlers EM wave radiowave enhanced growth wave particle interaction theory triggered wave magnetosphere whistlers bunching untrapped electrons VLF emissions phase bunching off-resonant bunching amplification mechanism }, mynotes={UNREAD}, }, @ARTICLE{WuDec89, author={Wu, C.S. and Yoon, P.H. and Freund, H.P.}, title={ A theory of electron cyclotron waves generated along auroral field lines observed by ground facilities }, journal={Geophysical Research Letters}, volume={16}, number={12}, year={1989}, month={Dec}, pages={1461-4}, abstract={ A generation mechanism for radio waves in the frequency range 150-700 kHz observed by ground facilities is suggested in terms of an electromagnetic electron cyclotron instability driven by auroral electrons. The excited waves can propagate downward along the ambient magnetic field lines and are thus observable with ground facilities. The trapped auroral electrons are supposed to play an important role in the generation process, because they give rise to a thermal anisotropy which consequently leads to the instability. The present work is a natural extension of the theory proposed earlier by Wu et al. (1983) which was discussed in a different context but may be used to explain the observed waves originated at low altitudes (<0.5 R/sub E/). This paper presents a possible wave generation mechanism valid in the entire auroral field line region of interest }, keywords={ ionosphere magnetosphere plasma wave generation radiowave emission LF MF magnetosphere plasma instability ionosphere theory electron cyclotron waves along auroral field lines generation mechanism radio waves electromagnetic electron cyclotron instability 150 to 700 kHz }, mynotes={UNREAD}, }, @ARTICLE{XuJul90, author={Xu, J.S. and Yeh, K.C.}, title={ Propagation of a VLF electromagnetic wave packet in a magnetoplasma }, journal={Journal of Geophysical Research}, volume={95}, number={A7}, year={1990}, month={Jul}, pages={10481-93}, abstract={ The wave packet is constructed by superposing a group of spectrum-weighted characteristic vectors. Accurate to the second order, a set of analytic expressions of the complex amplitude factor and field vectors for a Gaussian packet has been obtained. Based on these expressions, effects of dispersion and anisotropy on the vector property of wave field and the amplitude envelope are simulated. Numerical results show that the polarization of wave fields is varying when the packet moves and somewhat deviates from exact circular polarization in a plane transverse to the carrier wave vector, k/sub o/. The Gaussian envelope is found to rotate around the V/sub g/*k/sub o/ direction and to spread three dimensionally as it propagates }, keywords={ ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation radiowave propagation radiowave propagation magnetosphere ionosphere numerical model VLF electromagnetic wave packet magnetoplasma spectrum-weighted characteristic vectors analytic expressions complex amplitude factor field vectors Gaussian packet dispersion anisotropy amplitude envelope polarization }, mynotes={UNREAD}, }, @CONFERENCE{Yagitani89, author={Yagitani, S. and Nagano, I. and Kimura, I. and Mambo, M.}, title={ Full wave analysis of whistler mode waves excited by circularly polarized spherical waves incident from below }, booktitle={ISAP Japan 1989. Proceedings of the 1989 International Symposium onAntennas and Propagation}, volume={}, number={}, year={1989}, month={}, pages={489-92 vol.2}, abstract={ The polarization experiments conducted by Stanford University using the Antarctic Siple VLF transmitter have shown that the signals were observed at the geomagnetic conjugate point in Canada even if a left-hand circularly polarized wave is radiated from the transmitter, with an intensity 12 dB lower than those observed at the time of transmission of right-hand circular polarization. In order to quantitatively interpret this result, spatial energy distributions of whistler mode waves at an altitude of 105 km in the ionosphere are calculated by the full wave method, under the assumptions that spherical waves are radiated with a right- and a left-hand circular polarizations by crossed dipole antennas on the ground. It is found that the 12 dB difference in the signal strength at the conjugate point due to the difference in polarization is understood if the transmitted signal penetrates the bottom of the ionosphere horizontally about 80 km away from the transmitting point, where an end point of the field aligned VLF ducts may exist }, keywords={ electromagnetic wave polarisation ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation radio transmitters radiowave propagation whistlers full wave analysis magnetosphere EM wave propagation whistler mode waves circularly polarized spherical waves polarization experiments Stanford University Antarctic Siple VLF transmitter geomagnetic conjugate point Canada right-hand circular polarization spatial energy distributions altitude ionosphere left-hand circular polarizations crossed dipole antennas signal strength transmitted signal VLF ducts 80 km 105 km 3.48 kHz }, mynotes={UNREAD}, }, @ARTICLE{YamaguchiNov93, author={Yamaguchi, M. and Hattori, K. and Iwama, N. and Shimakura, S. and Hayakawa, M.}, title={ A new ground-based direction finding method using a linear reconstruction of wave distribution function of magnetospheric VLF/ELF radio waves }, journal={Transactions of the Institute of Electronics, Information and CommunicationEngineers B-II}, volume={J76B-II}, number={11}, year={1993}, month={Nov}, pages={880-9}, abstract={ A new direction finding method for magnetospheric VLF/ELF waves is proposed. It is based on the wave distribution function (WDF) using the linear regularization of Phillips-Tikhonov (1962,1963), which is aided with the generalized cross validation (GCV) in optimizing the reconstructed image. The results of numerical simulations for a single wave source show the effectiveness of the method, indicating that the criterion of minimum GCV is actually useful in obtaining well-approximated WDF's and that the linearity in the data processing leads to great saving of computation time }, keywords={ atmospheric techniques magnetospheric electromagnetic wave propagation radio direction-finding radiowave propagation magnetospheric VLF/ELF radio waves linear reconstruction wave distribution function ground-based direction finding linear regularization generalized cross validation reconstructed image numerical simulations wave source data processing }, mynotes={UNREAD}, }, @ARTICLE{YamamotoFeb91, author={Yamamoto, M. and Ito, Y. and Kishi, Y. and Sawada, A. and Kimura, I. and Nagano, I. and Kennai, E. and Okada, T. and Hashimoto, K.}, title={ k vector measurements of VLF signals by the satellite EXOS-D }, journal={Geophysical Research Letters}, volume={18}, number={2}, year={1991}, month={Feb}, pages={325-8}, abstract={ On board the EXOS-D (Akebono) satellite is a five channel PFX subsystem of VLF instruments, working to determine the wave normal or k vector and Poynting vector directions by measuring two components of E and three components of B fields using wire and loop antennas. In order to confirm the characteristics or capability of determining the k vector and the Poynting vector of a coherent VLF Omega signal transmitted from Australia have been analyzed. The observed Omega signal has been found to be right-handed polarized with the Poynting vector making a small angle with the geomagnetic field and lies nearly on the plane constructed by the geomagnetic field and k vector }, keywords={ atmospheric radiation atmospheric techniques ionospheric electromagnetic wave propagation ionospheric techniques magnetosphere magnetospheric electromagnetic wave propagation radiosignal radiowave Akebono measurement technique ionosphere magnetosphere artificial satellite k vector VLF EXOS-D PFX subsystem wave normal Poynting vector Poynting vector coherent VLF Omega signal right-handed polarized 3 to 30 kHz }, mynotes={UNREAD}, }, @ARTICLE{YamamotoDec75, title={ Nonlinear theory of a whistler wave }, journal={Journal of Plasma Physics}, volume={14}, number={}, year={1975}, month={Dec}, pages={543-9}, abstract={ Using the Dupree-Weinstock perturbed-orbit model of plasma turbulence, the diffusion equation describing the evolution of the average one-particle distribution function for whistler mode turbulence is derived. The numerical result for electron pitch-angle diffusion within this scheme leads to the conclusion that the effect of the resonance broadening due to perturbed orbits on the pitch-angle diffusion coefficient is not large compared with that evaluated by the unperturbed orbit in the whistler mode spectrum with a finite width. Based on the explicitly evaluated resonance function, the effects of this broadening on the growth rate for the whistler wave are also discussed }, keywords={ electromagnetic wave propagation in plasma plasma turbulence whistlers whistler wave plasma turbulence diffusion equation resonance function nonlinear theory Dupree Weinstock perturbed orbit model electron pitch angle diffusion }, mynotes={UNREAD}, }, @ARTICLE{YamanakaJan84, author={Yamanaka, Y. and Hayakawa, M.}, title={ Measurements of wave normal directions of magnetospheric VLF emissions observed on board satellites }, journal={Electronics and Communications in Japan}, volume={67}, number={1}, year={1984}, month={Jan}, pages={56-8}, abstract={ The wave normal directions of magnetospheric VLF/ELF chorus have been determined by using data from the geostationary satellite GEOS 2. They will provide useful information on the emission generation mechanism }, keywords={ artificial satellites atmospheric radiation magnetospheric electromagnetic wave propagation radiowave propagation wave normal directions magnetospheric VLF emissions satellites VLF/ELF chorus geostationary satellite GEOS 2 emission generation mechanism }, mynotes={UNREAD}, }, @ARTICLE{YamanakaNov83, author={Yamanaka, Y. and Hayakawa, M.}, title={ Measurements of wave normal directions of magnetospheric VLF emissions observed on board satellites }, journal={Transactions of the Institute of Electronics and Communication Engineers ofJapan, Part B}, volume={J66B}, number={11}, year={1983}, month={Nov}, pages={1428-9}, abstract={ Determination of wave normal directions of magnetospheric VLF emissions (chorus emissions) have been made for the first time at the geomagnetic equator, considered as the source region, with the satellite GEOS 2. The analyses have suggested different mechanisms for the upper and lower band chorus }, keywords={ atmospheric radiation magnetosphere upper band chorus magnetosphere radiowave emissions mechanism wave normal directions VLF emissions satellites geomagnetic equator GEOS 2 lower band chorus }, mynotes={UNREAD}, }, @ARTICLE{YoshidaMar80, author={Yoshida, T. and Ohtsu, J. and Hayakawa, M.}, title={ On the conditions of triggering VLF emissions by a natural whistler }, journal={Proceedings of the Research Institute of Atmospherics, Nagoya University}, volume={27}, number={}, year={1980}, month={Mar}, pages={31-48}, abstract={ Discusses the conditions of triggering VLF emissions by a natural whistlers with variable frequency. The interaction time is defined by using the variation of unperturbed phase angle, which is determined by the spatial inhomogeneity of the medium and the wave frequency variation. Sample calculations of the interaction time are made for frequencies below the noise frequency on L=4. A comparison of the interaction time with the bunching time has shown that VLF emissions are possibly triggered even by a weak whistler around 3 kHz in a very restricted range of geomagnetic latitude far from the equator in the upstream side of the electron. The study of the phase variations including the finite wave amplitude based on the complete equations of motion has confirmed that the condition that the interaction time exceeds the bunching time would be a threshold for phase bunching of electrons by a whistler, and hence triggering VLF emissions }, keywords={ atmospheric radiation magnetosphere whistlers triggering VLF emission natural whistler interaction time magnetosphere }, mynotes={UNREAD}, }, @ARTICLE{ZhangDec93, author={Zhang, Y.L. and Matsumoto, H. and Omura, Y.}, title={ Linear and nonlinear interactions of an electron beam with oblique whistler and electrostatic waves in the magnetosphere }, journal={Journal of Geophysical Research}, volume={98}, number={A12}, year={1993}, month={Dec}, pages={21353-63}, abstract={ Both linear and nonlinear interactions between oblique whistler, electrostatic, quasi-upper hybrid mode waves and an electron beam are studied by linear analyses and electromagnetic particle simulations. In addition to a background cold plasma, the authors assumed a hot electron beam drifting along a static magnetic field (B/sub 0/). Growth rates of the oblique whistler, oblique electrostatic, and quasi-upper hybrid instabilities were first calculated. They found that there are four kinds of unstable mode waves for parallel and oblique propagations. They are the electromagnetic whistler mode wave (WW1), the electrostatic whistler mode wave (WW2), the electrostatic mode wave (ESW), and the quasi-upper hybrid mode wave (UHW). When the angle theta between the wave vector k and B/sub 0/ is small enough (2500 Hz. The warm plasma model assumes a two-component plasma, with an isotropic cold component and a bi-Maxwellian warm component. The effect of the warm component is to change the wave dispersion relation, allowing the production of the higher-frequency risers. A portion of the anisotropy required to produce the high-frequency emissions can also be provided by a loss cone distribution. The chorus source is estimated from this cyclotron resonance theory to be located near the equatorial plane }, keywords={ atmospheric electron precipitation atmospherics cyclotron resonance VLF chorus emissions cyclotron resonance model electron microburst precipitation narrowband rising frequency emissions microburst electron precipitation rocket observations AD 1993 05 06 magnetosphere cold plasma cyclotron resonance interaction warm plasma model wave dispersion relation loss cone distribution 1 to 4 kHz }, mynotes={UNREAD}, } @ARTICLE{HattoriFeb93, author={Hattori, K. and Hayakawa, M.}, title={ Direction-finding measurements of magnetospheric VLF chorus emissions and analysis of their generation and propagation mechanism }, journal={Electronics and Communications in Japan, Part 1 (Communications)}, volume={76}, number={2}, year={1993}, month={Feb}, pages={73-86}, abstract={ Chorus is one of the most important VLF/ELF emissions in the magnetosphere, but several points are still unsolved concerning their generation and propagation mechanisms. In the present paper, the near-equatorial direction-finding measurements made on board a satellite are studied and it is confirmed that the rising tone chorus is generated at theta (the angle between the wave normal and Earth's magnetic field) approximately 0 degrees by the cyclotron resonance interaction with the energetic electrons. These results support the theory of Helliwell (1967). Moreover, the direction-finding measurements of the rising tone chorus are carried out on the GEOS 1 satellite in the off-equatorial regions. Their generation and propagation mechanism are studied with the help of three-dimensional ray-tracing computations and these results are compared with the corresponding results of OGO 5 direction-finding measurements by Burton et al. As a result, the observations by OGO 5 indicate that after the generation of chorus at the equator with wave-normal direction theta /sub 0/ approximately 0 degrees , it reaches the satellite in ducted propagation along the magnetic field line, whereas the results of GEOS 1 suggest that the waves are generated in a wider region near the equator with comparatively smaller theta /sub 0/ (30 degrees - 40 degrees , at the most 50 degrees ) and that the subsequent propagation is nonducted in the magnetosphere. Finally, the direction finding measurements and the ray-tracing computation are suggested to be very important in the study of generation and propagation of various emissions generated in the magnetosphere }, keywords={ atmospheric radiation magnetosphere magnetospheric electromagnetic wave propagation plasma radiowave propagation magnetospheric VLF chorus emissions propagation generation ELF near-equatorial direction-finding measurements rising tone chorus cyclotron resonance interaction energetic electrons GEOS 1 OGO 5 ray-tracing computations magnetic field line ducted propagation nonducted propagation }, mynotes={UNREAD}, } @ARTICLE{HattoriApr92, author={Hattori, K. and Hayakawa, M.}, title={ Direction finding measurements of magnetospheric VLF chorus emissions and their generation and propagation mechanism }, journal={Transactions of the Institute of Electronics, Information and CommunicationEngineers B-II}, volume={J75B-II}, number={4}, year={1992}, month={Apr}, pages={217-28}, abstract={ Chorus is one of the most popular natural VLF/ELF emissions in the magnetosphere. The previous near-equatorial direction finding measurements have indicated that chorus is generated around the equator with its wave normal being nearly aligned with the magnetic field by the electron cyclotron instability. Its subsequent propagation in the outer magnetosphere is discussed. Wave normal directions for rising tone chorus observed in the off-equatorial regions are presented, and they are compared with the results of three-dimensional ray-tracing computations. The authors conclude that the subsequent propagation of chorus generated around the equator is ducted on some occasions, but non-ducted on other occasions. Finally, the use of direction finding is found to be very important in the study of generation and propagation of magnetospheric emissions }, keywords={ atmospherics magnetosphere magnetospheric electromagnetic wave propagation radio direction-finding radiowave propagation wave normal directions nonducted propagation ducted chorus propagation magnetospheric VLF chorus emissions propagation mechanism VLF/ELF emissions magnetosphere direction finding measurements magnetic field electron cyclotron instability rising tone chorus off-equatorial regions three-dimensional ray-tracing equator magnetospheric emissions }, mynotes={UNREAD}, } @ARTICLE{KulkarniJan92, author={Kulkarni, V.H. and Das, J.H.}, title={ Very low frequency (VLF) chorus emissions: a topical survey }, journal={Surveys in Geophysics}, volume={13}, number={1}, year={1992}, month={Jan}, pages={35-46}, abstract={ Reviews the observations of natural VLF radio emission termed 'chorus', that have been made on the ground and abroad satellites, and also their dependence on various geomagnetic phenomena. The current theoretical interpretations of the generation and propagation of chorus signals are highlighted }, keywords={ atmospheric radiation magnetosphere reviews VLF radiowave emission magnetosphere chorus VLF radio emission generation propagation 3 to 30000 kHz }, mynotes={UNREAD}, } @ARTICLE{SinghDec91, title={ Generation of VLF hiss and chorus in Jupiter's magnetosphere }, journal={Indian Journal of Radio & Space Physics}, volume={20}, number={6}, year={1991}, month={Dec}, pages={438-43}, abstract={ Using plasma and field parameters corresponding to L=8, temporal growth rates of VLF waves have been computed for a non-Maxwellian electron distribution function in the Jovian magnetosphere. It is found that the presence of bi-Maxwellian electron distributions leads the generation of VLF chorus just below one-half of the electron gyrofrequency and the presence of a nonthermal drifted Maxwellian tail leads to an instability below one-fourth of the electron gyrofrequency. The computed results are in good agreement with those reported by the Voyager 1 and 2 plasma wave experiments }, keywords={ astrophysical radiation mechanisms Jupiter planetary atmospheres radioastronomy atmosphere Jupiter radio emission nonMaxwellian electron distribution function plasma VLF hiss chorus magnetosphere bi-Maxwellian electron distributions nonthermal drifted Maxwellian tail instability }, mynotes={UNREAD}, } @ARTICLE{LalmaniDec88, author={Lalmani, Kishen and K. and Khosa, P.N.}, title={ Low latitude discrete VLF chorus-an indicator of the wave-particle interactions in the inner magnetosphere }, journal={Indian Journal of Physics, Part B}, volume={62B}, number={4}, year={1988}, month={Dec}, pages={536-40}, abstract={ Discrete chorus emissions are very low frequency (VLF) electromagnetic waves that are commonly observed outside the plasmasphere. The authors present the analysis of the discrete chorus type emissions observed probably for the first time at low latitude and discuss their role as a diagnostic tool for studying the plasma processes in the inner magnetosphere. The discrete chorus emissions recorded during strong magnetic storm on 6-8 March, 1986 at the low latitude ground station Gulmarg (geomag. lat; 24 degrees 26'N) are selected for the present investigation }, keywords={ atmospherics magnetosphere magnetospheric electromagnetic wave propagation plasma plasma diagnostics AD 1986 03 06 to 08 atmospherics VLF chorus wave-particle interactions inner magnetosphere discrete chorus type emissions low latitude diagnostic tool plasma magnetic storm Gulmarg }, mynotes={UNREAD}, } @ARTICLE{Jiricek86, author={Jiricek, F. and Triska, P. and Titova, E.E. and Yakhnina, T.A. and Maltseva, O.A.}, title={ On latitudinal variations of temporal characteristics of the VLF chorus in the upper ionosphere }, journal={Studia Geophysica et Geodaetica}, volume={30}, number={4}, year={1986}, month={}, pages={411-16}, abstract={ The elements of the VLF chorus, observed simultaneously at a ground station and satellite in polar orbit can be used to determine the differences in the arrival times of waves Delta tau and their dependence on latitude. Mostly Delta tau does not change noticeably over a wide range of latitudes; however, in some cases it may increase appreciably at low value of L. Model computations of the propagation time, based on the assumption that the source of the chorus is located close to the equatorial plane, have indicated the possibility of explaining the increase in Delta tau at low latitudes by the presence of a step in the electron density profile close to this plane }, keywords={ atmospheric radiation atmospheric structure atmospherics electron density ionosphere ionospheric electromagnetic wave propagation magnetosphere magnetospheric electromagnetic wave propagation polar-orbiting satellite Interkosmos 19 topside ionosphere waves arrival times chorus source region magnetosphere plasmapause equatorial electron density step VLF waves propagation paths density step L-shell latitudinal variations temporal characteristics VLF chorus upper ionosphere ground station propagation time equatorial plane electron density profile 500 to 1000 km 1.5 to 4 kHz 2.7 to 5.0 Earthradii }, mynotes={UNREAD}, } @ARTICLE{Jiricek86, author={Jiricek, F. and Triska, P. and Malteseva, O.A. and Titova, E.E. and Yakhnina, T.A.}, title={ Connection between the upper ionospheric region of VLF chorus occurrence and the plasmapause position }, journal={Studia Geophysica et Geodaetica}, volume={30}, number={4}, year={1986}, month={}, pages={404-10}, abstract={ The occurrence zone of the VLF chorus in the upper ionosphere appears at L-shells lower than the plasmapause position L/sub pp/; with increasing geomagnetic activity the spatial dimension of the zone diminishes, its upper boundary being shifted in correspondence with the plasmapause position, the lower remaining practically without change (L=2.0-2.5). Calculations of propagation paths show that the similarity of the VLF chorus spectrum at different upper-ionospheric latitudes as well as the large spatial dimension of the zone of observation can be explained as special features in the propagation of VLF waves from an equatorial source, starting in the vicinity of the plasmapause with different initial normal angles }, keywords={ atmospheric radiation atmospheric structure atmospherics ionosphere magnetic storms magnetosphere magnetospheric electromagnetic wave propagation chorus zone spatial dimension ionospheric L-shells chorus zone upper boundary shift VLF waves propagation lower boundary equatorial VLF source topside ionosphere plasmapause VLF emission magnetosphere EM wave propagation Interkosmos-19 satellite upper ionospheric region VLF chorus occurrence plasmapause position increasing geomagnetic activity propagation paths VLF chorus spectrum upper-ionospheric latitudes initial normal angles 500 to 1000 km 1.5 to 4 kHz 3.4 to 5.0 Earthradii }, mynotes={UNREAD}, } @ARTICLE{ImhofAug86, author={Imhof, W.L. and Voss, H.D. and Walt, M. and Gaines, E.E. and Mobilia, J. and Datlowe, D.W. and Reagen, J.B.}, title={ Slot region electron precipitation by lightning, VLF chorus and plasmaspheric hiss }, journal={Journal of Geophysical Research}, volume={91}, number={A8}, year={1986}, month={Aug}, pages={8883-94}, abstract={ Energetic electrons are precipitated from the slot region of the radiation belts by a variety of mechanisms, including short duration wave bursts associated with lightning and chorus and more slowly varying plasmaspheric hiss. Characteristics of the nightside short duration precipitation events, including their favored occurrence at certain longitudes in the Northern Hemisphere, indicate that they are predominantly associated with lightning. The dayside events seem to relate primarily to VLF chorus. A study is made of various characteristics of the short duration precipitation burst, namely, the longitude and L shell variations, the day/night differences, the energies of spectral maxima and the rapid spectral variations with time. In addition, the total loss rates of electrons from the radiation belts are obtained from the measured energy spectra and pitch angle distributions. An assessment is made of the relative importance of the bursts as a loss mechanism for slot region electrons in comparison to the more slowly varying precipitation processes }, keywords={ atmospheric electron precipitation atmospheric radiation atmospherics lightning magnetosphere radiation belts magnetosphere atmosphere atmospherics radiation electron precipitation lightning VLF chorus plasmaspheric hiss slot region radiation belts short duration wave bursts nightside Northern Hemisphere longitude spectral maxima total loss rates energy spectra pitch angle }, mynotes={UNREAD}, } @ARTICLE{InanApr86, title={ Jovian VLF chorus and Io torus aurora }, journal={Journal of Geophysical Research}, volume={91}, number={A4}, year={1986}, month={Apr}, pages={4543-50}, abstract={ A test particle model of the cyclotron resonance interaction of waves and trapped radiation belt particles is used to estimate the energetic electron fluxes precipitated by Jovian VLF chorus waves observed on the Voyager 1 and 2 spacecraft near the Io torus. The precipitation fluxes induced by 1-s-long chorus wave packets at L approximately=7.6 and 8.6 are estimated to be bursts of approximately 5 s duration with a peak of 0.3-3 and 0.7-7 ergs/cm/sup 2/ s that consist of electrons of approximately 5-100 keV energy and that arrives at the ionosphere approximately 15 s after the generation of the chorus wave at the equatorial plane. The effects in the Jovian ionosphere of the chorus-induced precipitation are estimated using existing ionospheric models }, keywords={ Jupiter planetary atmospheres planetary satellite atmospheres Jupiter planetary atmosphere radiowave emission plasma torus magnetosphere electron precipitation VLF chorus Io torus aurora test particle model cyclotron resonance interaction radiation belt energetic electron fluxes ionosphere }, mynotes={UNREAD}, } @ARTICLE{RoederNov85, author={Roeder, J.L. and Benbrook, J.R. and Bering, E.A. and III and Sheldon, W.R.}, title={ X-ray microbursts and VLF chorus }, journal={Journal of Geophysical Research}, volume={90}, number={A11}, year={1985}, month={Nov}, pages={10975-82}, abstract={ On January 4, 1978, at 1140 UT, a SuperArcas sounding rocket was launched from Siple Station, Antarctica (L=4.2, 76 degrees S, 84 degrees W), during a geomagnetically disturbed period (K/sub p/=6-) with intense X-ray and VLF chorus activity. The parachuted payload observed an intense microburst precipitation event of 10-minute duration. These data have been correlated with measurements of VLF chorus by receivers on the ground at both Siple and its magnetic conjugate point, Roberval, Quebec. Detailed one-to-one correspondence between the microbursts and the chorus was not a consistent feature of the data. A significant correlation exists between the Siple X-ray precipitation and the Roberval VLF waves with an arrival time delay of 0.1+or-0.3 seconds }, keywords={ atmospheric electron precipitation atmospheric radiation ionosphere magnetosphere ionosphere radionoise X-ray microburst AD 1978 01 04 electron precipitation VLF chorus microburst precipitation event conjugate }, mynotes={UNREAD}, } @ARTICLE{SazhinApr85, author={Sazhin, S.S. and Hayakawa, M. and Tanaka, Y.}, title={ On the fine structure of the ground-based VLF chorus as an indicator of the wave particle interaction processes in the magnetospheric plasma }, journal={Planetary and Space Science}, volume={33}, number={4}, year={1985}, month={Apr}, pages={385-6}, abstract={ Smirnova (1984) pointed out that chorus emissions can be used as a diagnostic tool for determinating several magnetospheric plasma parameters including the L-shell of chorus generation, the large scale electric field and the anisotropy of magnetospheric electrons. The author presents three comments on the corresponding methods of diagnostics proposed by Smirnova }, keywords={ atmospheric electricity atmospheric techniques atmospherics magnetosphere plasma AD 1978 11 to 1978 01 atmospherics electrons atmospheric technique fine structure VLF chorus wave particle interaction magnetospheric plasma L-shell electric field }, mynotes={UNREAD}, } @ARTICLE{SmirnovaApr84, title={ Fine structure of the ground-observed VLF chorus as an indicator of the wave-particle interaction processes in the magnetospheric plasma }, journal={Planetary and Space Science}, volume={32}, number={4}, year={1984}, month={Apr}, pages={425-38}, abstract={ The results of investigations of chorus type VLF emissions in the subauroral conjugate regions and along the meridional profile near the plasmapause projection are summarized in order to connect the peculiarities of ground-observed VLF chorus with plasma processes in the magnetosphere during substorm development. A method of determining the location of the instability region in the magnetosphere is suggested, based on the measurement of the upper boundary frequency and the ground-observed VLF chorus (UBF-method). The dynamics of chorus spectra during the substorm development are investigated. On the basis of the observed regularities a phenomenological model of the development of the VLF chorus source is constructed. Some magnetospheric plasma parameters such as plasma density, large-scale electric field, etc., are calculated. The calculated and typical measured parameters are shown to be conformable. The diagnostic possibilities of VLF chorus are discussed }, keywords={ atmospheric radiation atmospherics magnetic storms magnetosphere plasma magnetic storms atmospherics radiowave emission AD 1964 to 1972 Sogra magnetic observatory Soviet Union Kerguelen Island USSR Indian Ocean EM waves ground-observed VLF chorus wave-particle interaction processes magnetospheric plasma chorus type VLF emissions subauroral conjugate regions meridional profile plasmapause projection substorm development upper boundary frequency chorus spectra chorus source plasma parameters plasma density large-scale electric field }, mynotes={UNREAD}, } @ARTICLE{InanAug83, author={Inan, U.S. and Helliwell, R.A. and Kurth, W.S.}, title={ Terrestrial versus Jovian VLF chorus; a comparative study }, journal={Journal of Geophysical Research}, volume={88}, number={A8}, year={1983}, month={Aug}, pages={6171-80}, abstract={ The relevant parameters of the magnetospheres of Jupiter and Earth are studied from the point of view of wave-particle resonant interactions that are believed to be responsible for the generation of VLF chorus emissions observed on Voyager-1. Using existing models of the cold and energetic plasma distributions in the Jovian magnetosphere, expressions for the wave-particle interaction length (L/sub I/) and the nonlinearity parameter ( rho ) are derived. Values of these parameters are compared with those computed for the Earth's magnetosphere. It is found that the typical interaction lengths are at least 2-5 times larger in the Jovian than in the terrestrial magnetosphere. Also, the wave intensity necessary to reach the threshold of nonlinearity in the Jovian magnetosphere was found to be up to 5-100 times lower }, keywords={ Jupiter magnetosphere planetary atmospheres radioastronomy Earth Jupiter planet radiowave emission wave particle interaction chorus burst growth rate VLF chorus resonant interactions generation magnetosphere wave-particle interaction length nonlinearity parameter threshold }, mynotes={UNREAD}, } @ARTICLE{Gorshkov80, title={ Energetic and dynamic characteristics of the envelope of VLF-chorus bursts }, journal={Geomagnetizm i Aeronomiya}, volume={20}, number={5}, year={1980}, month={}, pages={}, abstract={ Several types of VLF chorus are identified that differ from each other in their energy spectra and dynamic characteristics. Some of the characteristics of the magnetospheric plasma and of electron streams responsible for the generation of VLF emission are estimated from VLF data }, keywords={ atmospheric radiation ionosphere magnetosphere chorus ionospheric noise EM wave emission burst magnetosphere dynamic characteristics envelope VLF }, mynotes={UNREAD}, } @ARTICLE{TsurudaFeb82, author={Tsuruda, K. and Machida, S. and Terasawa, T. and Nishida, A. and Maezawa, K.}, title={ High spatial attenuation of the Siple transmitter signal and natural VLF chorus observed at ground-based chain stations near Roberval, Quebec }, journal={Journal of Geophysical Research}, volume={87}, number={A2}, year={1982}, month={Feb}, pages={742-50}, abstract={ The field intensity of the Siple transmitter signal was measured at four stations along the geomagnetic meridian passing about 100 km west of Roberval, Quebec, during about 1 month from July 10 to August 10, 1979. The distance between adjacent stations was 70-90 km, and the L values covered by the four stations were from 4.15 to 4.7. It is found that the field intensity of the Siple transmitter signal falls off very rapidly with distance. A typical rate of attenuation with distance is found to be nearly 1 order of magnitude higher than the value expected from the Earth-ionosphere cavity propagation theory. The intensity of VLF chorus was measured at six stations along the same meridian on August 8, 1979. The two stations were added to the north of the four stations, and their L values were 4.85 and 5.1. The chorus intensity was found to fall off with distance almost with the same rate as the Siple signal }, keywords={ ionospheric electromagnetic wave propagation whistlers VLF radiowave emission ionosphere radiowave propagation AD 1979 07 to 08 whistler mode coupling spatial attenuation chorus Earth-ionosphere cavity }, mynotes={UNREAD}, } @ARTICLE{RosenbergJul81, author={Rosenberg, T.J. and Siren, J.C. and Matthews, D.L. and Marthinsen, K. and Holtet, J.A. and Egeland, A. and Carpenter, D.L. and Helliwell, R.A.}, title={ Conjugacy of electron microbursts and VLF chorus }, journal={Journal of Geophysical Research}, volume={86}, number={A7}, year={1981}, month={Jul}, pages={5819-32}, abstract={ Information on the location of microburst source regions is limited. One measurement at L approximately=8.5 placed the source within 4 R/sub E/ of the ionosphere. Measurements at 535 degrees geographic latitude) and an enhanced equatorial ionization anomaly (EIA) on the low-latitude side (<35 degrees geographic latitude) were observed over Japan both by the NNSS and by the meridian chain of ionosonde stations. This enhancement of the EIA suggests the penetration of magnetospheric electric fields during the storms. Corresponding to the anomalous TEC decreases in the northern part of Japan, ionosonde stations in this region observed specific disturbances of ionospheric variation characterized by simultaneous decreases of f/sub 0/F/sub 2/ and increases of h'F. These features of ionospheric variations on the high-latitude side can be attributed to the upward escape of ionospheric plasma caused by the heating and evacuation mechanisms, which are induced by depletion of the plasmasphere and the resulting access of ring current particles to low latitudes }, keywords={ aurora ionospheric disturbances magnetic storms magnetosphere ionospheric disturbances low-latitude auroral events magnetospheric processes geomagnetic storms AD 1989 10 21 AD 1992 05 10 total electron content US Navy Navigation Satellite System NNSS ionosonde data Japanese meridian chain geomagnetic disturbances anomalous TEC equatorial ionization anomaly magnetospheric electric field penetration F/sub 2/-layer critical penetration frequency ionospheric variations ionospheric plasma escape plasma heating plasmasphere ring current particles }, mynotes={UNREAD}, } @ARTICLE{ElphicAug96, author={Elphic, R.C. and Weiss, L.A. and Tnomsen, M.F. and McComas, D.J. and Moldwin, M.B.}, title={ Evolution of plasmaspheric ions at geosynchronous orbit during times of high geomagnetic activity }, journal={Geophysical Research Letters}, volume={23}, number={16}, year={1996}, month={Aug}, pages={2189-92}, abstract={ The evolution of the plasmasphere, the region of relatively dense cold plasma surrounding the Earth, is strongly dependent on magnetospheric activity. The authors report on plasmaspheric evolution as observed at geosynchronous orbit in association with magnetopause crossings and storm sudden commencements (SSCs). The occurrence frequency distributions at geosynchronous orbit of both magnetopause-associated and SSC-associated plasmaspheric ions is peaked near 1400 LT, with an overall range from 1000 LT to beyond 1800 LT. This is greatly skewed from the average plasmaspheric distribution at 6.6 R/sub E/, which peaks closer to 1800 LT. The evolution of SSC-associated plasmaspheric ions is tracked using a superposed epoch analysis: lower-activity SSCs produce minor changes from the pre-SSC local time distribution; after geomagnetically-effective SSCs, the ions appear almost immediately at earlier local times, spanning the late morning to dusk local time sector for hours. These observations are consistent with (1) a push of plasmaspheric material inward over the spacecraft due to magnetospheric compression and (2) the prompt penetration of a convection electric field }, keywords={ magnetosphere plasmaspheric ion evolution plasmasphere geosynchronous orbit high geomagnetic activity high magnetic activity dense cold plasma magnetospheric activity magnetopause crossing storm sudden commencement SSC plasmaspheric ions }, mynotes={UNREAD}, } @ARTICLE{JordanovaJan96, author={Jordanova, V.K. and Kistler, L.M. and Kozyra, J.U. and Khazanov, G.V. and Nagy, A.F.}, title={ Collisional losses of ring current ions }, journal={Journal of Geophysical Research}, volume={101}, number={A1}, year={1996}, month={Jan}, pages={111-26}, abstract={ The time evolution of the ring current population during the recovery phase of a typical moderate magnetic storm is studied, using a newly developed kinetic model for H/sup +/, He/sup +/ and O/sup +/ ions which includes nonequatorially mirroring particles. The bounce-averaged distribution function is defined for variables that are accessible to direct measurement, and some useful formulas for calculating the total energy and number density of the ring current are derived. The bounce-averaged kinetic equation is solved, including losses due to charge exchange with neutral hydrogen and Coulomb collisions with thermal plasma along ion drift paths. Time-dependent magnetospheric electric fields and anisotropic initial pitch angle distributions are considered. The generation of ion precipitating fluxes is addressed, a process that is still not completely understood. It is shown that both the decrease of the distribution function due to charge exchange losses and the buildup of a low-energy population caused by Coulomb collisions proceed faster for particles with smaller pitch angles. The maximum of the equatorial precipitating fluxes occurs on the nightside during the early recovery phase and is found to be of the order of 10/sup 4/-10/sup 5/ cm/sup -2/ sr/sup -1/ s/sup -1/ keV/sup -1/. The mechanisms considered in this paper indicate that magnetospheric convection plays the predominant role in causing ion precipitation; Coulomb scattering contributes significantly to the low-energy ion precipitation inside the plasmasphere }, keywords={ atmospheric ion precipitation electrojets magnetosphere radiation belts magnetosphere electrojet collisional loss ring current ion temporal evolution recovery phase magnetic storm substorm kinetic model He/sup +/ O/sup +/ H/sup +/ nonequatorially mirroring particles bounce-averaged distribution function bounce-averaged kinetic equation electric field anisotropic initial pitch angle distribution ion precipitation magnetospheric convection He O H }, mynotes={UNREAD}, } @ARTICLE{LiuFeb94, author={Liu, H. and Kokubun, S. and Hayashi, K.}, title={ Equatorial electromagnetic emission with discrete spectra near harmonics of oxygen gyrofrequency during magnetic storm }, journal={Geophysical Research Letters}, volume={21}, number={3}, year={1994}, month={Feb}, pages={225-8}, abstract={ Equatorial electromagnetic ELF emissions in the frequency range around the oxygen ion gyrofrequency were observed in the low altitude plasmasphere (L=1.5 approximately 2.5) during magnetic storms with high ring current activity by triaxial search coil and single component electric field instruments on board the Akebono satellite. A particular type of ELF emission occurs with a multi-band spectral structure around the local gyrofrequency (F/sub O+/) of the oxygen ion (O/sup +/) during the main phase of the magnetic storm. The multi-band emissions are localized in the morning sector and often consist of several spaced frequency bands closely related to the local gyro-harmonics of oxygen ion (O/sup +/), with a fundamental frequency of F/sub O+/ or 2F/sub O+/. The frequency of each band is dependent on the local magnetic field variation along the satellite orbit, and the spacing between the bands is almost equal to F/sub O+/ or 2F/sub O+/. The emissions are probably generated by the terrestrial oxygen ions composing the ring current area }, keywords={ atmospheric electricity atmospheric radiation atmospherics magnetic storms magnetosphere oxygen magnetosphere equatorial ELF emissions ELF atmospherecs ELF emission bands spacing magnetosphere ring current magnetic storm main phase AD 1989 11 to 1992 02 geomagnetic Dst-index variations magnetic storm electromagnetic ELF emissions low altitude plasmasphere ring current activity Akebono satellite multi-band spectral structure multi-band emissions morning sector spaced frequency bands fundamental frequency local magnetic field variation satellite orbit 1.5 to 2.5 Earthradii 6 to 10 Mm 0 to 50 Hz O/sup +/ gyrofrequency harmonics emission O/sup +/ local gyrofrequency }, mynotes={UNREAD}, } @ARTICLE{FokNov93, author={Fok, M.-C. and Kozyra, J.U. and Nagy, A.F. and Rasmussen, C.E. and Khazanov, G.V.}, title={ Decay of equatorial ring current ions and associated aeronomical consequences }, journal={Journal of Geophysical Research}, volume={98}, number={A11}, year={1993}, month={Nov}, pages={19381-93}, abstract={ The decay of the major ion species which constitute the ring current is studied by solving the time evolution of their distribution functions during the recovery phase of a moderate geomagnetic storm. Only equatorially mirroring particles are considered. Particles are assumed to move subject to E*B and gradient drifts. They also experience losses along their drift paths. Two loss mechanisms are considered: charge exchange with neutral hydrogen atoms and Coulomb collisions with thermal plasma in the plasmasphere. Thermal plasma densities are calculated with a plasmaspheric model employing a time-dependent convection electric field model. Charge exchange is found to be the major loss mechanism for the ring current ions; however the important effects of Coulomb collisions on both the ring current and thermal populations are also presented. The model predicts the formation of a low-energy (< 500 eV) ion population as a result of energy degradation caused by Coulomb collisions of the ring current ions with the plasmaspheric electrons; this population may be one source of the low-energy ions observed during active and quiet periods in the inner magnetosphere. The energy transferred to plasmaspheric electrons through Coulomb collisions with ring current ions is believed to be the energy source for the electron temperature enhancement and the associated 6300 AA emission in the subauroral region. The calculated energy deposition rate is sufficient to produce a subauroral electron temperature enhancement and SAR arc emissions that are consistent with observations of these quantities during moderate magnetic activity levels }, keywords={ atmospheric elementary particle precipitation magnetic storms magnetosphere plasma equatorial ring current ions major ion species decay time evolution distribution functions recovery phase moderate geomagnetic storm equatorially mirroring particles gradient drifts loss mechanisms charge exchange Coulomb collisions thermal plasma plasmasphere plasma densities time-dependent convection electric field model thermal population energy degradation inner magnetosphere energy deposition rate subauroral electron temperature enhancement SAR arc emissions 500 eV }, mynotes={UNREAD}, } @ARTICLE{VillalonJun91, author={Villalon, E. and Burke, W.J.}, title={ Near-equatorial pitch angle diffusion of energetic electrons by oblique whistler waves }, journal={Journal of Geophysical Research}, volume={96}, number={A6}, year={1991}, month={Jun}, pages={9655-67}, abstract={ The pitch angle scattering of trapped, energetic electrons by obliquely propagating whistler waves in the equatorial regions of the plasmasphere is investigated. Storm-injected electrons moving along field lines near the equator interact with electromagnetic waves whose frequencies are Doppler-shifted to some harmonic of the cyclotron frequency. Relativistic, quasi-linear theory is applied to obtain self-consistent equations describing the temporal evolution of waves and particles over time scales which are longer than the particle bounce time and group time delay of the waves. The equilibrium solutions and their stability are studies, considering the reflection of the waves by the ionosphere and the coupling of multiple harmonic resonances. The contributions of nonlocal wave sources are also included in the theory }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation plasma radiation belts whistlers magnetosphere radiation belt pitch angle diffusion energetic electrons oblique whistler waves equatorial regions plasmasphere cyclotron frequency quasi-linear theory self-consistent equations temporal evolution reflection ionosphere multiple harmonic resonances nonlocal wave sources }, mynotes={UNREAD}, } @ARTICLE{SwiderJul90, title={ Precipitating and trapped ions and electrons observed at 840 km during the great magnetic storm of February 1986 }, journal={Journal of Geophysical Research}, volume={95}, number={A7}, year={1990}, month={Jul}, pages={10417-25}, abstract={ A detailed picture is presented of the equatorward boundaries of the auroral ovals at dawn, morning, dusk, and evening for the three most disturbed days of February 1986. North-south symmetry for the boundaries of keV particles was good, and the differences between the ion and electron boundaries agreed with statistics which show the ion edge slightly equatorward of the electron edge at dusk, with the reverse for dawn. The electron boundary was most equatorward of the ion boundary for morning. Best symmetry and least difference were for evening, the sector nearest the central plasma sheet. Ions with energies from thermal to several hundred electron volts penetrated inward to L=1.2. Initial penetration was confined mainly, if not exclusively, to the dawn sector. The sudden appearance of low-energy ions deep in the plasmasphere at dusk and evening after storm maximum suggests corotation from a plasmapause as low as L=1.7 at dawn }, keywords={ atmospheric electron precipitation atmospheric ion precipitation aurora magnetic storms aurora ion precipitation electron precipitation ionosphere topside AD 1986 02 auroral oval trapped ions great magnetic storm equatorward boundaries plasmasphere plasmapause 840 km }, mynotes={UNREAD}, } @ARTICLE{MillerDec83, author={Miller, N.J. and Mayr, H.G. and Harris, I.}, title={ Calculated stormtime variations in plasmaspheric thermal ion composition }, journal={Journal of Geophysical Research}, volume={88}, number={A12}, year={1983}, month={Dec}, pages={10233-7}, abstract={ Model calculations describing stormtime variations in the Earth's dayside plasmasphere are used to examine variations in ion composition. The model storm is initiated by high-latitude thermospheric heating that generates meridional winds that carry neutral species, momentum, and energy equatorward. The thermosphere acts on the plasmasphere through collisional transfer of momentum and through chemical reactions between neutral species and ions. Over latitudes near the region of thermospheric heating, the thermosphere-plasmasphere coupling processes cause enhancement in the density of oxygen ions while protons are being lost. Meanwhile, densities of oxygen ions and protons near the equator are increasing together, almost in phase. The largest enhancements in ion density develop at latitudes near 45 degrees invariant for both oxygen and hydrogen }, keywords={ ionosphere disturbed ionosphere magnetic storm upper atmosphere stormtime variations thermal ion composition dayside variations thermospheric plasmasphere coupling processes }, mynotes={UNREAD}, } @ARTICLE{SinghOct83, author={Singh, N. and Schunk, R.W.}, title={ Numerical simulations of counterstreaming plasmas and their relevance to interhemispheric flows }, journal={Journal of Geophysical Research}, volume={88}, number={A10}, year={1983}, month={Oct}, pages={7867-77}, abstract={ The collisionless expansion of counterstreaming plasmas has been studied by solving the self-consistent set of Vlasov and Poisson equations in one dimension. The motivation for the study is to elucidate some of the basic physical processes which may occur during the initial refilling of depleted flux tubes after a magnetic storm. The simulation geometry consisted of two high-density H/sup +/-O/sup +/-electron plasmas (conjugate ionospheres) separated by a low density H/sup +/-electron plasma (equatorial plasmasphere). The numerical simulations indicate that the ion beams in the counterstreaming plasmas are remarkably stable with respect to the ion acoustic instability, which is in agreement with the linear instability theory. However, in the presence of a magnetic field, the linear instability theory predicts that the counterstreaming suprathermal forerunner ions can excite ion cyclotron waves, which in turn can thermalize and trap the suprathermal forerunners. Such a mechanism may be operating in the equatorial plasmasphere shortly after magnetic storms }, keywords={ ionosphere magnetosphere plasma flow recovery phase disturbance ionosphere magnetosphere plasmasphere counterstreaming plasmas interhemispheric flows collisionless expansion Vlasov Poisson equations initial refilling depleted flux tubes magnetic storm }, mynotes={UNREAD}, } @ARTICLE{MaedaNov82, author={Maeda, K. and Anderson, R.R.}, title={ A broadband VLF burst associated with ring current electrons }, journal={Journal of Geophysical Research}, volume={87}, number={A11}, year={1982}, month={Nov}, pages={9120-8}, abstract={ During the periods after the maximum phase of geomagnetic storms on 2 April 1972 a broadband VLF emission burst has been observed by the equatorially orbiting satellite S/sup 3/-A (Explorer 45) along its inbound plasmapause crossings. The frequency band broadening takes place just outside of the nighttime plasmasphere, where the density of cold plasma has been known to be very low during the laser phase of a geomagnetic storm. A burst type broadening of VLF emission lasting less than ten minutes was observed. The magnetic field component of this emission is very weak and the frequency spreads below the local half electron cyclotron frequency. Corresponding enhancement of the anisotropic ring-current electrons is also very sudden and limited below the order of 10 keV without significant velocity dispersion, in contrast to the gradual broadening events. The cause of this type of emission band spreading can be attributed to the generation of the quasi-electrostatic whistler mode emissions of short wavelength by hot bi-maxwellian electrons surging into the domain of relatively low density magnetized cold plasma }, keywords={ atmospheric radiation magnetosphere broadband burst radiowave emission magnetosphere AD 1972 04 VLF ring current plasmapause whistler mode }, mynotes={UNREAD}, } @ARTICLE{BalsigerApr80, author={Balsiger, H. and Eberhardt, P. and Geiss, J. and Young, D.T.}, title={ Magnetic storm injection of 0.9- to 16-keV/e solar and terrestrial ions into the high-altitude magnetosphere }, journal={Journal of Geophysical Research}, volume={85}, number={A4}, year={1980}, month={Apr}, pages={1645-62}, abstract={ The Geos 1 ion composition experiment has surveyed the plasma composition in the energy per charge range below 16 keV/e at all local times and at L=3-8. During quiet and moderately disturbed times, H/sup +/ is the dominant species with a few percent of heavy (M/Q>1) ions. Substorms and storms increase the relative amount of heavy ions and, occasionally, they cannot become the dominant species in the outer magnetosphere. Two sources, the solar wind (characterized by /sup 4/He/sup ++/) and the ionosphere (characterized by O/sup +/), give on the average comparable contributions to storm time plasma, although individual storms one or the other may dominate. Data presented here suggest that high-altitude thermal plasma or the plasmasphere (characterized by He/sup +/ and O/sup ++/) must be considered as a third source. The behaviour of the ring current during storm conditions is also discussed }, keywords={ atmospheric composition atmospheric electricity atmospheric precipitation magnetic storms magnetosphere magnetosphere ion composition plasma composition solar wind ionosphere plasmasphere high altitude ion composition plasmasphere magnetic storm substorm ion precipitation }, mynotes={UNREAD}, } @ARTICLE{ParkJul78, author={Park, C.G. and Carpenter, D.L. and Wiggin, D.B.}, title={ Electron density in the plasmasphere: whistler data on solar cycle, annual, and diurnal variations }, journal={Journal of Geophysical Research}, volume={83}, number={A7}, year={1978}, month={Jul}, pages={3137-44}, abstract={ Whistler data are used to present a statistical view of equatorial plasmaspheric electron density n/sub eq/ and associated tube electron content N/sub T/ (defined as the number of electrons in a geomagnetic flux tube of 1 cm/sup 2/ cross-sectional area at 1000 km altitude and extending to the magnetic equator). The data were acquired between 1959 and 1973 at Byrd (L approximately=7), Eights (L approximately=4), and Siple (L approximately=4), Antarctica, and from Stanford, California (L approximately=2). The plasmaspheric n/sub eq/ profile beyond L approximately=3 is dominated by variations associated with magnetic disturbances and subsequent recovery. In the aftermath of disturbances the plasmasphere tends to be divided into an inner 'saturated' region, which is in equilibrium with the underlying ionosphere in a diurnal average sense, and an outer 'unsaturated' region, which is still filling with plasma from below. In the outer plasmasphere beyond approximately 3.5 R/sub E/, diurnal variations appear as relatively small effects superimposed on larger storm-associated variations }, keywords={ electron density magnetic storms magnetosphere solar-terrestrial relationships whistlers whistler data solar cycle diurnal variations equatorial plasmaspheric electron density tube electron content geomagnetic flux tube Byrd Eights Siple Stanford, California magnetic disturbances electron density annual variations magnetic storms inner saturated region plasma refilling outer unsaturated region storm recovery phase plasmasphere/ionosphere equilibrium }, mynotes={UNREAD}, } @ARTICLE{WebbNov77, author={Webb, D.C. and Lanzerotti, L.J.}, title={ Temporal variations in slant total plasmasphere content and their relationship to the ring current intensity and the plasmapause }, journal={Journal of Geophysical Research}, volume={82}, number={32}, year={1977}, month={Nov}, pages={5201-7}, abstract={ The time dependence of the total electron content of the plasmasphere, as determined from the radio beacon experiment on the ATS 6 satellite is studied for an 11-month period in 1974-1975 (Fritz, 1976). Close temporal associations are often observed between increases (decreases) in the ring current intensity as measured by the ring current index Dst and decreases (increases) in the plasmasphere content. The recovery of the plasmasphere after six geomagnetic storm periods is examined; the deduced filling rate is found comparable to the total flux tube filling rates reported by Park (1973) from whistler studies. The rate of the equatorial plasmasphere filling and the rate of decay of the ring current intensity appear to be related, at least for the six events examined. Finally, an empirical relationship between the total plasmasphere content and the equatorial plasmapause position at 1200 LT is derived }, keywords={ electron density magnetic storms magnetosphere plasmasphere ring current intensity plasmapause total electron content radio beacon experiment ATS 6 satellite geomagnetic storm periods magnetosphere temporal variations Faraday rotation }, mynotes={UNREAD}, } @ARTICLE{SmithJun74, author={Smith, E.J. and Frandsen, A.M.A. and Tsurutani, B.T. and Chan, K.W.}, title={ Plasmaspheric hiss intensity variations during magnetic storms }, journal={Journal of Geophysical Research}, volume={79}, number={16}, year={1974}, month={Jun}, pages={2507-10}, abstract={ The storm time intensity variations of ELF electromagnetic emissions have been studied by using the Ogo 6 search coil magnetometer. Low-latitude signals exhibit a sharp low-frequency cutoff and are identified as plasmaspheric hiss. Such waves show pronounced intensification during the recovery phase of magnetic storms but remain close to background levels during the storm main phase. This behavior is consistent with cyclotron resonant generation within the plasmasphere as the latter expands into the intensified belt of outer zone electrons during the storm recovery }, keywords={ atmospherics magnetic storms magnetosphere noise plasmaspheric hiss intensity variations magnetic storms ELF electromagnetic emissions cutoff Ogo 6 search coil magnetometer background levels storm main phase cyclotron resonant generation outer zone electrons storm recovery }, mynotes={UNREAD}, } @ARTICLE{SmithMar74, author={Smith, P.H. and Hoffman, R.A.}, title={ Direct observations in the dusk hours of the characteristics of the storm time ring current particles during the beginning of magnetic storms }, journal={Journal of Geophysical Research}, volume={79}, number={7}, year={1974}, month={Mar}, pages={966-71}, abstract={ The characteristic features of the initial enhancement of the storm time ring current particles in the evening hours are consistent with flow patterns resulting from a combination of inward convection, gradient drift, and corotation, which carries plasma sheet protons into low L values near midnight and the higher-energy proton component into the plasmasphere and through the evening hours. Data from four magnetic storms during the early life of S/sup 3/-A (Explorer 45) when the local time of apogee was in the afternoon and evening hours show that protons with lower magnetic moments penetrate deeper into the magnetosphere until a lower limit, determined by the corotation and gradient drift forces, is reached. Such particle motions produce the stable energy-dependent inner boundary of the ring current protons inside the plasmapause in the dusk sector and also provide the mechanism for energy injection into the ring current region. From the analyses of the pitch angle distributions it is evident that charge exchange and wave-particle interactions are not the dominant causes of this inner boundary. Observations of plasma sheet protons and electrons at altitudes just beyond the measured plasmapause are also consistent with the resulting flow patterns }, keywords={ magnetic storms magnetosphere direct observations dusk hours storm time ring current particles magnetic storms initial enhancement evening hours flow patterns Explorer 45 magnetosphere plasmapause dusk sector pitch angle distributions plasma sheet }, mynotes={UNREAD}, } @ARTICLE{ParkApr73, title={ Whistler observations of the recovery of the plasmasphere following a magnetic storm }, journal={EOS Trans. Am. Geophys. Union (USA), EOS Transactions of the AmericanGeophysical Union}, volume={54}, number={4}, year={1973}, month={Apr}, pages={416}, abstract={ The recovery of the plasmasphere following a large magnetic storm is examined in detail using Antarctic whistlers, which provide information on electron concentrations between L approximately 2 to 6. It is found that the filling proceeds at a fairly uniform rate until the plasmasphere reaches a well-defined density level where an equilibrium with the underlying ionosphere prevails. The time required to reach this equilibrium is related to the plasmaspheric tube volume, and varies from approximately 2 days at L=2.5 to approximately 7 days at L=4 }, keywords={ magnetic storms magnetosphere whistlers whistler observations magnetic storm Antarctic whistlers electron concentrations density level ionosphere plasmasphere recovery }, mynotes={UNREAD}, } @ARTICLE{TheisApr73, author={Theis, R.F. and Brace, L.H.}, title={ ISIS-II observations during the August 4, 1972 storm }, journal={EOS Trans. Am. Geophys. Union (USA), EOS Transactions of the AmericanGeophysical Union}, volume={54}, number={4}, year={1973}, month={Apr}, pages={416}, abstract={ ISIS-II measurements of plasma concentration, composition and temperature during the week of 3-8 August 1972 have been used to study the movements of the plasmapause during an intense geomagnetic storm. From these measurements in a circular, polar orbit at 1400 kilometers altitude it is concluded that the plasmasphere is disturbed and heated at all latitudes down to the equator, L=1.25 in this orbit }, keywords={ magnetic storms magnetosphere ISIS-II observations August 4, 1972 plasma concentration composition temperature plasmapause intense geomagnetic storm polar orbit }, mynotes={UNREAD}, } @ARTICLE{KoonsJul72, author={Koons, H.C. and McPherson, D.A.}, title={ Observation of very-low-frequency whistler-mode waves in the region of the radiation-belt slot }, journal={Journal of Geophysical Research}, volume={77}, number={19}, year={1972}, month={Jul}, pages={3475-82}, abstract={ Following a sudden-commencement magnetic storm, band-limited VLF emissions between 3.9 and 10.4 kHz were observed at high altitudes within the plasmasphere (L approximately 2.5 to 3.6) by a receiver aboard spacecraft OV1-14 (1968-26B). The maximum spectral intensities of 1.1 m gamma /Hz/sup 1/2/ and 2.8 mu v/Hz/sup 1/2/ on the magnetic and electric antennas, respectively, occur in the 5.6-kHz channel. The waves can resonantly interact with energetic electrons above approximately 50 kev at L=2.5, and the measured wave intensities are sufficiently high to account for the short lifetimes of medium-energy electrons in the slot region between the inner and outer Van Allen radiation zones. A comparison with ground-based VLF data suggests that the waves are generated by band-limited amplification of incoherent noise }, keywords={ magnetic storms radiation belts whistlers incoherent noise maximum spectral intensities VLF whistler mode waves radiation belt slot sudden commencement magnetic storm medium energy electrons OV1 14 (1968 26B) }, mynotes={UNREAD}, } @ARTICLE{EvansMay72, title={ Measurements of horizontal drifts in the E and F regions at Millstone Hill }, journal={Journal of Geophysical Research}, volume={77}, number={13}, year={1972}, month={May}, pages={2341-52}, abstract={ At Millstone Hill (42.6 degrees N, 71.5 degrees W) an oblique-incidence incoherent-scatter radar system has been employed to observe the drift of the ionospheric plasma in the E and F regions in directions across the earth's magnetic field. These measurements yield the true macroscopic motion of the ions rather than the motion of waves impressed in the plasma, but, owing to sensitivity limitations, measurements could be made only during the daytime when the electron density is large. It is found that the drift appears to be independent of altitude above about 180 km; this result suggests that the drift is caused by an electrostatic field. On the average the drift has an amplitude of about 25 m/sec (1 mv/m), and the direction rotates in a clockwise sense through 360 degrees in 12 hours. The drifts observed at 130 km appear similar to the drifts in the F region, but in azimuth the direction lags behind the drift observed in the F region by 50 degrees -60 degrees . It appears that the electric field responsible for the drift in the F region is generated in the E region by the dynamo action of the solar semidiurnal (2,2) tidal oscillation. On one day electric fields of magnetospheric origin developed following a magnetic storm sudden commencement. The clockwise progression of the drift was then reversed, and the drift reached 200 m/sec toward the west. This motion may be connected with the reported sunward surges of the plasma in the plasmasphere bulge at times of substorms }, keywords={ E-region F-region ionospheric measurement E-region solar semidiurnal tidal oscillation horizontal drifts Millstone Hill radar system ionospheric plasma macroscopic motion daytime electrostatic field magnetic storm sudden commencement F-region }, mynotes={UNREAD}, } @ARTICLE{ScarfApr72, author={Scarf, F.L. and Fredricks, R.W. and Smith, E.J. and Frandsen, A.M.A. and Serbu, G.P.}, title={ Ogo 5 observations of LHR noise, emissions, and whistlers near the plasmapause at several earth radii during a large magnetic storm }, journal={Journal of Geophysical Research}, volume={77}, number={10}, year={1972}, month={Apr}, pages={1776-93}, abstract={ On May 15, 1969, Ogo 5 crossed the plasmapause during a major storm that produced severe geomagnetic disturbances (Kp up to 8-), large and rapid variations in ring-current intensity (as measured by Dst), intense low-latitude aurora, and persistent SAR arcs. Near the highly structured plasmasphere boundary, the electric- and magnetic-field sensors on Ogo 5 detected lower-hybrid-resonance noise bursts, whistlers, ELF hiss, and other discrete signals or emissions. Some LHR noise bursts were associated with whistlers, and these high- altitude phenomena resembled the corresponding ionospheric ones. This report contains a description of the VLF observations. It is also shown that intense ULF magnetic signals were present near the plasmapause, and we attempt to relate these observations to the predictions of various theories of proton ring-current decay and SAR-arc formation }, keywords={ atmospherics magnetic storms magnetosphere upper atmosphere intense low latitude aurora persistent SAR arcs lower hybrid resonance noise bursts ELF hiss VLF observations ring current intensity proton ring current decay SAR arc formation Ogo 5 observations emissions whistlers plasmapause several earth radii large magnetic storm discrete signals }, mynotes={UNREAD}, } @ARTICLE{SchulzJan72, author={Schulz, M. and Koons, H.C.}, title={ Thermalization of colliding ion streams beyond the plasmapause }, journal={Journal of Geophysical Research}, volume={77}, number={1}, year={1972}, month={Jan}, pages={248-54}, abstract={ On field lines that are closed, oppositely directed plasma flows analogous to the polar wind have recently been detected in the ionospheric trough regions. Those originating from conjugate regions of the ionosphere will encounter each other near the equatorial plane. For a background plasma of sufficiently low equatorial density (N/sub 0/or approximately=20 cm/sup -3/) thermalization occurs via coulomb collisions. These flows, together with the complementary thermalization mechanisms not previously analyzed, constitute a rapid means of replenishing the plasmasphere (dN/sub 0//dt approximately 10/cm/sup 3/ hr) during the recovery phase of a magnetic storm. Upward flows have long been suspected of playing such a role. Beyond the quiet-day plasmapause location, the conditions for two-stream instability appear to be present continuously, since the counterstreaming plasmas are simultaneously convected to the magnetospheric boundary }, keywords={ atomic collision processes ionosphere magnetosphere plasma thermalization colliding ion streams plasmapause oppositely directed plasma flows ionospheric trough regions }, mynotes={UNREAD}, } @ARTICLE{TaylorApr72, title={ Some observed characteristics of the light ion trough }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={53}, number={4}, year={1972}, month={Apr}, pages={461}, abstract={ A primary feature of the ion composition results from the OGO-2, 4, and 6 satellites is the light ion trough, in which the mid latitude concentrations of H/sup +/ and He/sup +/ typically decrease by at least an order of magnitude, dropping to levels of 10/sup 3/ ions/cm/sup 3/ or less near 60 degrees dipole latitude (L=4), associated with the position of the plasmapause. In contrast to the 'main trough' in N/sub e/ which has been observed largely as a nightside phenomenon, the light ion trough persists both during day and night. For daytime winter conditions, and for all seasons during night, the mid latitude ionization decrease is a pronounced feature. During dayside summer and equinox, the rate of ionization decrease with latitude is comparatively gradual, and the trough boundary is less well defined, particularly for quiet magnetic conditions. In response to magnetic storms, the light ion trough minimum moves equatorward, and deepens, consistent with earlier evidence of the contraction of the plasmasphere in response to storm time enhancements in magnetospheric plasma convection. The fact that a pronounced light ion trough is observed under conditions for which the dominant ion O/sup +/ may exhibit little or no simultaneous decrease appears to explain why studies of the 'main trough' in topside distributions of N/sub e/ and N/sub i/ may at times have been inconclusive in relating the total ionization minimum wih the mechanism of the plasmapause }, keywords={ atmospheric ionisation magnetosphere light ion trough mid latitude concentrations H/sup +/ He/sup +/ plasmapause ionization decrease magnetic storms contraction plasmasphere storm time enhancements magnetospheric plasma convection }, mynotes={UNREAD}, } @ARTICLE{TaylorOct71, author={Taylor, H.A. and Jr., Grebowsky and J.M. and Walsh, W.J.}, title={ Structured variations of the plasmapause: Evidence of a corotating plasma tail }, journal={Journal of Geophysical Research}, volume={76}, number={28}, year={1971}, month={Oct}, pages={6806-14}, abstract={ Direct measurements of the pole-to-pole distributions of topside thermal protons obtained with the Ogo-4 ion composition experiment, near local midnight, reveal sharply structured variations of the plasmasphere boundary. With increasing L values the proton density distributions may exhibit a pronounced inner trough, in which the ambient H/sup +/ concentrations decrease by an order of magnitude near L=2 and subsequently recover to midlatitude concentration levels before a more pronounced and persistent trough is encountered at higher L positions. The time evolution of the trough boundaries observed during a sample of five consecutive satellite orbits following the peak of the magnetic storm on September 21, 1967, suggests that the observed structure results from a plasma tail or elongation of the plasmasphere that tends to corotate with the earth }, keywords={ atmospheric ionisation F-region ionospheric measurement plasma plasmapause topside thermal protons ion composition experiment local midnight inner trough ambient H/sup +/ concentrations time evolution magnetic storm plasma tail corotate pole to pole distributions }, mynotes={UNREAD}, } @ARTICLE{CarpenterJul71, author={Carpenter, D.L. and Park, C.G. and Arens, J.F. and Williams, D.J.}, title={ Position of the plasmapause during a stormtime increase in trapped energetic (E>280 keV) electrons }, journal={Journal of Geophysical Research}, volume={76}, number={19}, year={1971}, month={Jul}, pages={4669-73}, abstract={ Reports on the position of the plasmapause relative to the region of appearance of enhanced fluxed of energetic (E>280 keV) electrons during the magnetic storm of June 15, 1965. The plasmapause was measured near the prime geomagnetic meridian by whistler techniques; the trapped energetic electrons were detected by the satellite 1963-38C in polar orbit at 1100 km altitude. As the stormtime reduction in plasmasphere radius occurred, the electron fluxes increased in a region that was apparently exterior to the diminishing plasmasphere. The plasmapause position appears to have been adjacent to the region of inflation of the magnetosphere reported by Cahill from Explorer 26 magnetometer data. This relationship is similar to that deduced from the Ogo 3 measurements of Frank (ring current particles) and Taylor and his colleagues (thermal ion density) }, keywords={ magnetosphere plasmapause stormtime increase trapped electrons magnetic storm }, mynotes={UNREAD}, } @ARTICLE{ChappellApr71, author={Chappell, C.R. and Harris, K.K. and Sharp, G.W.}, title={ Ogo 5 measurements of the plasmasphere during observations of stable auroral red arcs }, journal={Journal of Geophysical Research}, volume={76}, number={10}, year={1971}, month={Apr}, pages={2357-65}, abstract={ Ambient H/sup +/ ion concentration was measured in the plasmasphere during two intense magnetic storms that were accompanied by occurrences of stable auroral red (SAR) arcs. The H/sup +/ ion density profiles were measured by the ion mass spectrometer on Ogo 5 during the periods October 29 to November 7, and October 10 to 17, 1968. Correlations of the H/sup +/ ion densities in the plasmasphere were made with the D/sub st/ and kp magnetic indices and with ground observations of the 6300-A SAR arcs. This study shows that the SAR arcs are observed in the rapid recovery phase of the storm in the 10-20 hours following injection of ring current particles and that the plasmasphere is drastically reduced in size during the storm, with the SAR are located in L value near the position of the plasmapause. The arc is found to occur in the ionosphere at the base of flux tubes that have ambient H/sup +/ ion densities of 100-1000 ions/cm/sup 3/ near the magnetic equatorial plane }, keywords={ aurora hydrogen ions magnetic storms magnetosphere plasmasphere stable auroral red arcs H/sup +/ concentration magnetic storms density profiles recovery phase injection ring current particles }, mynotes={UNREAD}, } @ARTICLE{ChappellNov70, author={Chappell, C.R. and Carpenter, D.L.}, title={ Observations of the plasmasphere during the substorm of August 15, 1968 }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={51}, number={11}, year={1970}, month={Nov}, pages={810}, abstract={ Direct measurements of the H/sup +/ ion density made from the OGO-5 satellite have been combined with OGO-4 VLF measurements to determine the changes in plasmapause position during the substorm of 0716 U.T., August 15, 1968. The VLF measurements appear to give information concerning the inward drift of the plasmapause associated with the substorm. The substorm onset was detected by the OGO-5 magnetometer which was in the earth's magnetotail. During the period following the onset of the storm, the exact plasmapause profile was measured at 0315 and 1727 L.T. by the light ion mass spectrometer on OGO-5. These correlated measurements display some of the plasmasphere characteristics during this substorm period and indicate the probable presence of increased magnetospheric convection electric fields }, keywords={ magnetic storms magnetosphere upper atmosphere plasmasphere observations substorm H/sup +/ ion density motion magnetosphere }, mynotes={UNREAD}, } @ARTICLE{KoonsNov70, author={Koons, H.C. and Schulz, M.}, title={ Thermalization of colliding ion streams beyond the plasmapause }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={51}, number={11}, year={1970}, month={Nov}, pages={804}, abstract={ On field lines that are closed, oppositely directed plasma flows analogous to the polar wind can originate from conjugate regions of the ionosphere and encounter each other near the equatorial plane. For a background plasma of sufficiently low equatorial density (N/sub o/100 nT. It is claimed that a dominant dual-peak (DP) distribution exists in the solar cycle variability of these storms, with one peak occurring at the late ascending phase of the cycle or at solar maximum and another at the early descending phase of the cycle. Although the present study is restricted to intense storms, their distribution including moderate events for the interval 1965-1985, in terms of Dst values <-50 nT,, also shows evidence of a dual-peak distribution. The origin of the dual-peak distribution of intense storms is associated to a similar dual-peak distribution obtained for large-amplitude (<-10 nT) and long-duration duration (>3 h) values of the negative B/sub z/ component of the interplanetary magnetic field computed for the interval 1970-1981 }, keywords={ magnetic storms solar activity solar-terrestrial relationships dual peak distribution AD 1879 to 1985 solar cycles 12 to 21 Sun solar terrestrial relationship intense geomagnetic storms solar cycle distribution Dst index aa index late ascending phase solar maximum early descending phase interplanetary magnetic field }, mynotes={UNREAD}, } @ARTICLE{FairfieldNov89, author={Fairfield, D.H. and Baker, D.N. and Craven, J.D. and Elphic, R.C. and Fennell, J.F. and Frank, L.A. and Richardson, I.G. and Singer, H.J. and Slavin, J.A. and Tsurutani, B.T. and Zwickl, R.D.}, title={ Substorms, plasmoids, flux ropes, and magnetotail flux loss on March 25, 1983: CDAW 8 }, journal={Journal of Geophysical Research}, volume={94}, number={A11}, year={1989}, month={Nov}, pages={15135-52}, abstract={ During a 9-hour period following a storm sudden commencement on March 25, 1983, six spacecraft near geosynchronous orbit, one over the pole, and three in the magnetotail monitored a complex sequence of magnetospheric variations. Magnetic field compressions associated with the sudden commencement were seen first by the near-Earth spacecraft and subsequently by the three downtail spacecraft. Ground magnetograms and synchronous orbit data are used to identify seven substorm intensifications during this geomagnetically active period. All the observations are consistent with the substorm-associated release of a plasmoid at a neutral line near 20 R/sub E/; however, the classical north-south variation of the plasma sheet magnetic field thought to be characteristic of the passage of a plasmoid in the deep tail was not seen in every case }, keywords={ magnetic storms magnetosphere plasma Coordinated Data Analysis Workshop 8 AD 1983 03 25 magnetic storm plasmoids flux ropes magnetotail flux loss CDAW 8 storm sudden commencement magnetospheric variations field compressions substorm intensifications plasma sheet }, mynotes={UNREAD}, } @ARTICLE{GonzalezJul89, author={Gonzalez, W.D. and Tsurutani, B.T. and Gonzalez, A.L.C. and Smith, E.J. and Tang, F. and Akasofu, S.-I.}, title={ Solar wind-magnetosphere coupling during intense magnetic storms (1978-1979) }, journal={Journal of Geophysical Research}, volume={94}, number={A7}, year={1989}, month={Jul}, pages={8835-51}, abstract={ The solar wind-magnetosphere coupling problem is investigated for the ten intense magnetic storms (Dst<-100 nT) that occurred during the 500 days (August 16, 1978 to December 28, 1979) studied by Gonzalez and Tsurutani (1987). This investigation concentrates on the ring current energization in terms of solar wind parameters, in order to explain the mod -Dst mod growth observed during these storms. Thus several coupling functions are tested as energy input and several sets of the ring current decay time-constant tau are searched to find best correlations with the Dst response. From the fairly large correlation coefficients found in this study, there is strong evidence that large scale magnetopause reconnection operates during such intense storm events and that the solar wind ram pressure plays an important role in the ring current energization }, keywords={ magnetic storms magnetosphere solar wind substorm magnetic storm AD 1978 AD 1979 intense magnetic storms solar wind-magnetosphere coupling ring current energization large scale magnetopause reconnection solar wind ram pressure }, mynotes={UNREAD}, } @ARTICLE{TangApr89, author={Tang, F. and Tsurutani, B.T. and Gonzalez, W.D. and Akasofu, S.I. and Smith, E.J.}, title={ Solar sources of interplanetary southward B/sub z/ Events responsible for major magnetic storms (1978-9) }, journal={Journal of Geophysical Research}, volume={94}, number={A4}, year={1989}, month={Apr}, pages={3535-41}, abstract={ Tsurutani et al. (1988) analyzed the ten intense interplanetary southward B/sub z/ events that led to major magnetic storms (Dst<-100 nT) during the 500-day interval, August 16, 1978, through December 28, 1979. The present authors report solar sources of the major storms and discuss their interplanetary effects. Seven of the sources of the ten major storms are flares and three are prominence eruptions. For three of the five southward B/sub z/ events in which the driver gases are the causes of the intense southward field leading to magnetic storms, the photospheric fields of the solar sources have no dominant southward component, indicating the driver gas fields do not always result from a simple outward convection of solar magnetic fields. Finally the authors compare the solar events and their resulting interplanetary shocks and find that the standard solar parameters do not correlate with the strengths of the resulting shocks at 1 AU. The implications are discussed }, keywords={ interplanetary magnetic fields magnetic storms photosphere shock waves solar flares solar magnetism solar prominences solar wind sun solar wind AD 1978 08 16 to 1979 12 28 interplanetary southward B/sub z/ Events major magnetic storms flares prominence driver gases photospheric fields convection magnetic fields interplanetary shocks 1 AU }, mynotes={UNREAD}, } @ARTICLE{TsurutaniAug88, author={Tsurutani, B.T. and Gonzalez, W.D. and Tang, F. and Akasofu, S.I. and Smith, E.J.}, title={ Origin of interplanetary southward magnetic fields responsible for major magnetic storms near solar maximum (1978-79) }, journal={Journal of Geophysical Research}, volume={93}, number={A8}, year={1988}, month={Aug}, pages={8519-31}, abstract={ The origins of the interplanetary southward B/sub z/ which cause the 10 major (D/sub st/<-100 nT) magnetic storms detected during the 500 days of study (August 16, 1978, to December 28, 1979) of the Gonzalez and Tsurutani (1987) work are examined in detail. A full complement of ISEE 3 plasma and field data, an 11-station AE index and the near-equatorial D/sub st/ index, are used in this analysis. It is found that the origins of the interplanetary southward B/sub z/ events are quite varied. If it is defined that the B/sub z/ event which leads to D/sub st/<-100 nT is 'the cause' of the storm, then one of the storm intensifications is caused by shock compression of preexisting southward interplanetary magnetic fields, four (or five) are related to driver gas magnetic fields, one (or two) are caused by shocked kinky heliospheric current sheets, two (or three) by turbulence or waves behind interplanetary shocks, and one possibly by draped fields associated with a noncompressive density enhancement event (without a shock or a high-speed stream). In simplistic terms, four (or five) storms are caused by driver gas fields, four by shocked (sheath) fields, and one possibly by high-intensity draped fields. In actuality, many of the interplanetary southward B/sub z/ and corresponding magnetic storm (D/sub st/) structures are more complex }, keywords={ interplanetary magnetic fields magnetic storms solar wind Earth southward IMF interplanetary magnetic field solar wind interaction magnetosphere major magnetic storm AD 1978 AD 1979 solar maximum southward B/sub z/ events shock compression }, mynotes={UNREAD}, } @ARTICLE{GonzalezSep87, author={Gonzalez, W.D. and Tsurutani, B.T.}, title={ Criteria of interplanetary parameters causing intense magnetic storms (D/sub st/<-100 nT) }, journal={Planetary and Space Science}, volume={35}, number={9}, year={1987}, month={Sep}, pages={1101-9}, abstract={ Ten intense magnetic storms (D/sub st/<-100 nT) occurred during the 500 days from 16 August 1978 to 28 December 1979. From ISEE-3 field and plasma data, it is found that the interplanetary causes of these storms are long-duration, large and negative (<-10 nT) IMF B/sub z/ events, associated with interplanetary duskward-electric fields >5 mV m/sup -1/, that last for intervals >3 h. Because a one-to-one relationship is found between these interplanetary events and intense storms, it is suggested that these criteria can be used as predictors of intense storms by an interplanetary monitor such as ISEE-3 }, keywords={ electric fields interplanetary magnetic fields magnetic storms AD 1978 08 16 to 1979 12 28 interplanetary magnetic fields solar wind intense magnetic storms 16 August 1978 to 28 December 1979 ISEE-3 interplanetary duskward-electric fields predictors interplanetary monitor }, mynotes={UNREAD}, } @ARTICLE{TsurutaniFeb75, author={Tsurutani, B.T. and Smith, E.J. and Thorne, R.M.}, title={ Electromagnetic hiss and relativistic electron losses in the inner zone }, journal={Journal of Geophysical Research}, volume={80}, number={4}, year={1975}, month={Feb}, pages={600-7}, abstract={ Broad band incoherent electromagnetic waves, called hiss, have been detected in the inner zone magnetosphere (L<2) by the search coil magnetometer aboard the polar orbiting satellite Ogo 6. The 200- to 1000-Hz emissions are detected almost exclusively during periods of strong geomagnetic activity such as storms and substorms, and the hiss intensity is generally related to the level of magnetic activity. Characteristic lifetimes of inner zone electrons, calculated in order of magnitude fashion on the basis of pitch angle diffusion into the loss cone driven by the cyclotron resonant interaction, are found to range between 10 and 60 days. These computed lifetimes are consistent with observation of enhanced electron between 10 and 60 days. These computed lifetimes are consistent with observations of enhanced electron precipitation for L>1.25 during storms. Although Coulomb scattering appears to be the dominant loss mechanism for L<1.25, pitch angles scattering by the hiss may make a significant contribution to electron losses, especially during magnetically active intervals. The source of inner zone hiss has also been investigated }, keywords={ atmospheric electron precipitation atmospherics magnetosphere electromagnetic hiss relativistic electron losses inner zone magnetosphere Ogo 6 storms substorms strong geomagnetic activity electron precipitation pitch angle diffusion }, mynotes={UNREAD}, } @ARTICLE{GurnettFeb95, author={Gurnett, D.A. and Persoon, A.M. and Randall, R.F. and Odem, D.L. and Remington, S.L. and Averkamp, T.F. and Debower, M.M. and Hospodarsky, G.B. and Huff, R.L. and Kirchner, D.L. and Mitchell, M.A. and Pham, B.T. and Phillips, J.R. and Schintler, W.J. and Sheyko, P. and Tomash, D.R.}, title={ The POLAR Plasma Wave Instrument }, journal={Space Science Reviews}, volume={71}, number={1-4}, year={1995}, month={Feb}, pages={597-622}, abstract={ The Plasma Wave Instrument on the POLAR spacecraft is designed to provide measurements of plasma waves in the Earth's polar regions over the frequency range from 0.1 Hz to 800 kHz. Three orthogonal electric dipole antennas are used to detect electric fields, two in the spin plane and one aligned along the spacecraft spin axis. A magnetic loop antenna and a triaxial magnetic search coil antenna are used to detect magnetic fields. Signals from these antennas are processed by five receiver systems: a wideband receiver, a high-frequency waveform receiver, a low-frequency waveform receiver, two multichannel analyzers; and a pair of sweep frequency receivers. Compared to previous plasma wave instruments, the POLAR Plasma Wave Instrument has several new capabilities. These include (1) an expanded frequency range to improve coverage of both low- and high-frequency wave phenomena, (2) the ability to simultaneously capture signals from six orthogonal electric and magnetic field sensors, and (3) a digital wideband receiver with up to 8-bit resolution and sample rates as high as 249 k samples s/sup -1/ }, keywords={ atmospheric measuring apparatus dipole antennas magnetosphere plasma diagnostics plasma waves Plasma Wave Instrument POLAR spacecraft plasma waves orthogonal electric dipole antennas electric fields magnetic loop antenna triaxial magnetic search coil antenna magnetic fields receiver systems wideband receiver high-frequency waveform receiver low-frequency waveform receiver multichannel analyzers sweep frequency receivers frequency range polar magnetosphere 0.1 Hz to 800 kHz }, mynotes={UNREAD}, } @ARTICLE{LeppingJul97, author={Lepping, R.P. and Burlaga, L.F. and Szabo, A. and Ogilvie, K.W. and Mish, W.H. and Vassiliadis, D. and Lazarus, A.J. and Steinberg, J.T. and Farrugia, C.J. and Janoo, L. and Mariani, F.}, title={ The Wind magnetic cloud and events of October 18-20, 1995: interplanetary properties and as triggers for geomagnetic activity }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14049-63}, abstract={ Late on October 18, 1995, a magnetic cloud arrived at the Wind spacecraft À175 R/sub E/ upstream of the Earth. The cloud had an intense interplanetary magnetic field that varied slowly in direction, from being strongly southward to strongly northward during its À30 hours duration, and a low proton temperature throughout. From a linear force free field model the cloud was shown to have a flux rope magnetic field line geometry, an estimated diameter of about 0.27 AU, and an axis that was aligned with the Y axis (GSE) within about 25 degrees . A corotating stream, in which large amplitude Alfven waves of about 0.5 hour period were observed, was overtaking the cloud and intensifying the fields in the rear of the cloud. The prolonged southward magnetic field observed in the early part of the cloud produced a geomagnetic storm of Kp=7 and considerable auroral activity late on October 18. About 8 hours in front of the cloud an interplanetary shock occurred. About three-quarters the way into the cloud another apparent interplanetary shock was observed. This report aims to support a variety of ISTP studies ranging from the solar origins of these events to resulting magnetospheric responses }, keywords={ interplanetary magnetic fields magnetic storms solar wind Wind magnetic cloud AD 1995 10 18 to 20 interplanetary properties geomagnetic activity trigger Wind spacecraft interplanetary magnetic field proton temperature linear force free field cloud model flux rope magnetic field line geometry cloud diameter corotating stream Alfven waves field intensification geomagnetic storm auroral activity interplanetary shock ISTP studies magnetospheric responses 175 Earthradii }, mynotes={UNREAD}, } @ARTICLE{CrookerMar97, author={Crooker, N.U. and Lazarus, A.J. and Phillips, J.L. and Steinberg, J.T. and Szabo, A. and Lepping, R.P. and Smith, E.J.}, title={ Coronal streamer belt asymmetries and seasonal solar wind variations deduced from Wind and Ulysses data }, journal={Journal of Geophysical Research}, volume={102}, number={A3}, year={1997}, month={Mar}, pages={4673-9}, abstract={ Solar wind measurements from Wind during March 1995 are combined with those from Ulysses' fast latitude scan to construct a map of the streamer belt. On the timescale of coronal change, the map is nearly a snapshot view of solar wind speed contours threaded by the trace of the heliospheric current sheet (HCS) in the +or-30 degrees heliolatitude range. The combined set of HCS crossings agrees remarkably well with the neutral line on the corresponding classical source surface map. The neutral line is displaced slightly southward, with latitudinal excursions ranging from -22 degrees to +17 degrees . In contrast, a line running through the locus of minimum speed, although following the general trend of the neutral line, is confined to lower latitudes and displaced slightly northward, ranging from -4 degrees to +13 degrees . The separation between the minimum speed locus and the neutral line marking the HCS was unexpected. Possible interplanetary and solar origins are discussed. The deduced asymmetries as well as coronal change between December and March were responsible for solar wind variations at Earth that mimicked the previously reported seasonal variation in Wind data and would have masked it had the observations been taken during the September equinox }, keywords={ solar corona solar wind seasonal solar wind variations coronal streamer belt asymmetries Wind data Ulysses data AD 1995 03 coronal change solar wind speed contours heliospheric current sheet neutral line classical source surface map latitudinal excursions minimum speed locus }, mynotes={UNREAD}, } @ARTICLE{SlavinApr97, author={Slavin, J.A. and Fairfield, D.H. and Lepping, R.P. and Szabo, A. and Reiner, M.J. and Kaiser, M. and Owen, C.J. and Phan, T. and Lin, R. and Kokubun, S. and Mukai, T. and Yamamoto, T. and Singer, H.J. and Romanov, S.A. and Buechner, J. and Iyemori, T. and Rostoker, G.}, title={ WIND, GEOTAIL, and GOES 9 observations of magnetic field dipolarization and bursty bulk flows in the near-tail }, journal={Geophysical Research Letters}, volume={24}, number={8}, year={1997}, month={Apr}, pages={971-4}, abstract={ The WIND, GEOTAIL, and GOES 9 spacecraft were all in the nightside magnetosphere and Interball was in the solar wind when a substorm began at \07:25 UT on April 18, 1996. WIND and GEOTAIL were located at downstream distances of X=-12 to -14 R/sub c/. The separation between these spacecraft was \10 R/sub c/ in the Y direction and less than \1 R/sub c/ in Z. While the northward field component at GOES 9 began to increase immediately, little or no dipolarization was observed at WIND and GEOTAIL until a series of very rapid B/sub z/ increases were observed \25-30 min later. About \1-2 min prior to each dipolarization event at WIND and GEOTAIL an earthward flow burst with peak speeds of 100-500 km/s was initiated. The duration of these bursty bulk flows were 1-7 min. These unique observations are interpreted as strong evidence for the existence of spatially localized, but sometimes temporally overlapping flow bursts in the near-tail during substorm expansion phase which result, cumulatively, in sufficient earthward magnetic flux transport to produce the well known dipolarization at geosynchronous orbit }, keywords={ magnetic storms magnetosphere plasma flow magnetosphere magnetotail WIND GEOTAIL GOES 9 observations magnetic field dipolarization bursty bulk flow near-tail magnetic tail magnetic storm onset nightside Interball AD 1996 04 18 dipolarization earthward flow burst temporally overlapping flow burst substorm expansion phase }, mynotes={UNREAD}, } @ARTICLE{WingleeApr97, author={Winglee, R.M. and Skoug, R.M. and Elsen, R.K. and Wilber, M. and Lin, R.P. and Lepping, R.L. and Mukai, T. and Kokubun, S. and Reme, H. and Sanderson, T.}, title={ IMF induced changes to the nightside magnetotail: a comparison between WIND/Geotail/IMP 8 observations and modeling }, journal={Geophysical Research Letters}, volume={24}, number={8}, year={1997}, month={Apr}, pages={947-50}, abstract={ A 3D global fluid simulation is used to investigate the changing magnetic field topology of the magnetotail as observed by Geotail and IMP 8. The event studied is of particular interest as the solar wind density and speed as observed by WIND were approximately constant so that the influence of the interplanetary magnetic field (IMF) can be isolated. Loading of the tail fields during southward IMF is seen at high latitudes with IMP 8 moving from the sheath into the magnetosphere while at low latitudes Geotail moves from the plasma sheet into the lobes. The reverse is true for northward turnings. The tail cross-section is shown to be elliptical during southward IMF with an eccentricity of about 0.2 and that this eccentricity is slowly eroded over a period of about an hour during northward IMF }, keywords={ interplanetary magnetic fields magnetosphere solar wind IMF solar wind magnetosphere interaction IMF induced change nightside magnetotail WIND Geotail IMP 8 observations model three dimensional fluid simulation global fluid simulation magnetic field topology interplanetary magnetic field }, mynotes={UNREAD}, } @ARTICLE{TerasawaApr97, author={Terasawa, T. and Fujimoto, M. and Mukai, T. and Shinohara, I. and Saito, Y. and Yamamoto, T. and Machida, S. and Kokubun, S. and Lazarus, A.J. and Steinberg, J.T. and Lepping, R.P.}, title={ Solar wind control of density and temperature in the near-Earth plasma sheet: WIND/GEOTAIL collaboration }, journal={Geophysical Research Letters}, volume={24}, number={8}, year={1997}, month={Apr}, pages={935-8}, abstract={ A statistical survey of GEOTAIL observations reveals the following properties of the near-Earth plasma sheet (-15-150R/sub E/ suggesting that the lobe magnetic field lines are linked with those in the magnetosheath across the magnetopause. Momentum and particles in the magnetosheath could enter the tail region across the magnetopause with high efficiency. The majority of observed Bz in the current sheet that separates the two distant tail lobes shows northward even beyond -150R/sub E/. This is contrary to the model of the quasi-steady reconnection around -100R/sub E/, but it cannot be readily concluded that the field lines in the plasma sheet are closed since the convection is predominantly directed tailward in the distant magnetotail }, keywords={ geomagnetism magnetosphere magnetotail global magnetic field structures tail lobe structures flaring angle magnetic field lines tail lobe expansion angle magnetopause magnetosheath current sheet quasi-steady reconnection plasma sheet convection Geotail data 10 to 150 Earthradii }, mynotes={UNREAD}, } @ARTICLE{NishidaDec94, title={ The GEOTAIL mission }, journal={Geophysical Research Letters}, volume={21}, number={25}, year={1994}, month={Dec}, pages={2871-3}, abstract={ Spacecraft specifications, science instruments, data handling procedures, and the orbit in the first 1.5 year of the operation are briefly described }, keywords={ artificial satellites atmospheric measuring apparatus data handling magnetosphere GEOTAIL mission spacecraft specifications science instruments data handling procedures orbit geomagnetic tail }, mynotes={UNREAD}, } @ARTICLE{Kokubun94, author={Kokubun, S. and Yamamoto, T. and Acuna, M.H. and Hayashi, K. and Shiokawa, K. and Kawano, H.}, title={ The Geotail magnetic field experiment }, journal={Journal of Geomagnetism and Geoelectricity}, volume={46}, number={1}, year={1994}, month={}, pages={7-21}, abstract={ The Geotail spacecraft carries a high-resolution magnetic field experiment to provide magnetic field data in the frequency range below 50 Hz. This experiment includes dual fluxgate magnetometers and a search coil magnetometer. Fluxgate sensors are mounted at distances of 4 m and 6 m from the spacecraft on a deployable mast to reduce spacecraft-generated noises. Both outboard and inboard fluxgate magnetometers have 7 automatically switchable ranges from +or-16 nT to +or-65536 nT (full scale) and resolutions equivalent to a 15-bit A/D conversion in each range. The basic sampling rate for the A/D conversion is 128 Hz for both magnetometers. Sampled signals are averaged to 16 vectors/s for the outboard magnetometer and 4 vectors/s for the inboard magnetometer for telemetry. Time-derivatives of magnetic field in the frequency range of 1-50 Hz (128 vector-samples/s) are acquired by the three-component search coil magnetometer (located on another mast), separated by 4 m from the spacecraft. Fluxgate data are continuously obtained at the same rate for both real-time and recorded modes of operation, while search coil data are only acquired in the real-time telemetry operation. The instruments were operated after the time of mast deployment on September 4, 1992. The details of this experiment and initial observations are presented }, keywords={ atmospheric measuring apparatus geomagnetism magnetometers magnetosphere Geotail magnetic field experiment dual fluxgate magnetometers search coil magnetometer resolutions sampling rate A/D conversion inboard magnetometer outboard magnetometer time-derivatives magnetotail magnetopause 16 to 65536 nT }, mynotes={UNREAD}, } @ARTICLE{BakerJul97, author={Baker, D.N. and Li, X. and Turner, N. and Allen, J.H. and Bargatze, L.F. and Blake, J.B. and Sheldon, R.B. and Spence, H.E. and Belian, R.D. and Reeves, G.D. and Kanekal, S.G. and Klecker, B. and Lepping, R.P. and Ogilvie, K. and Mewaldt, R.A. and Onsager, T. and Singer, H.J. and Rostoker, G.}, title={ Recurrent geomagnetic storms and relativistic electron enhancements in the outer magnetosphere: ISTP coordinated measurements }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14141-8}, abstract={ New, coordinated measurements from the International Solar-Terrestrial Physics (ISTP) constellation of spacecraft are presented to show the causes and effects of recurrent geomagnetic activity during recent solar minimum conditions. It is found using WIND and POLAR data that even for modest geomagnetic storms, relativistic electron fluxes are strongly and rapidly enhanced within the outer radiation zone of the Earth's magnetosphere. Solar wind data are utilized to identify the drivers of magnetospheric acceleration processes. Yohkoh solar soft X-ray data are also used to identify the solar coronal holes that produce the high-speed solar wind streams which, in turn, cause the recurrent geomagnetic activity. It is concluded that even during extremely quiet solar conditions (sunspot minimum) there are discernible coronal holes and resultant solar wind streams which can produce intense magnetospheric particle acceleration. As a practical consequence of this Sun-Earth connection, it is noted that a long-lasting E>1 MeV electron event in late March 1996 appears to have contributed significantly to a major spacecraft (Anik El) operational failure }, keywords={ magnetic storms magnetosphere radiation belts radiation belt AD 1996 recurrent magnetic storm recurrent geomagnetic storm relativistic electron enhancement outer magnetosphere ISTP coordinated measurements solar minimum conditions relativistic electron flux outer radiation zone high-speed solar wind stream high-speed stream }, mynotes={UNREAD}, } @ARTICLE{BakerApr97, author={Baker, D.N. and Klimas, A.J. and Vassiliadis, D. and Pulkkinen, T.I. and McPherron, R.L.}, title={ Reexamination of driven and unloading aspects of magnetospheric substorms }, journal={Journal of Geophysical Research}, volume={102}, number={A4}, year={1997}, month={Apr}, pages={7169-77}, abstract={ It is widely accepted that substorms consist of both directly driven and loading-unloading processes. However, a recent study has presented results which suggested that over 90% of the auoral electrojet (AE) variation was directly predictable from the solar wind variations alone. This would imply that only a small residual in the AE variability is due to internal magnetospheric dynamics. The present paper considers nonlinear dynamical models of the global solar wind-magnetosphere interaction and uses the observed, highly variable solar wind electric field (VBs) to drive the Faraday loop analogue model. It is found that it is critically important to include magnetotail unloading in the model in order to replicate the main features of geomagnetic activity: with just the driven response in the model, one does not obtain realistic time behavior of the model AL index. Thus these results show quite clearly that both driven and unloading processes must be included in a realistic model of geomagnetic activity }, keywords={ magnetic storms magnetosphere solar wind magnetosphere magnetic storm substorm unloading aspect driven aspect driving auoral electrojet variation solar wind variations internal magnetospheric dynamics nonlinear dynamical model solar wind magnetosphere interaction solar wind electric field Faraday loop analogue model magnetotail unloading geomagnetic activit AL index }, mynotes={UNREAD}, } @ARTICLE{Xinlin-LiApr97, author={Xinlin Li, Baker and D.N., Temerin and M., Larson and D., Lin and R.P., Reeves and G.D., Looper and M., Kanekal and S.G. and Mewaldt, R.A.}, title={ Are energetic electrons in the solar wind the source of the outer radiation belt? }, journal={Geophysical Research Letters}, volume={24}, number={8}, year={1997}, month={Apr}, pages={923-6}, abstract={ Using data from WIND, SAMPEX (Solar, Anomalous, and Magnetospheric Particle Explorer), and the Los Alamos National Laboratory (LANL) sensors onboard geostationary satellites, the authors investigate the correlation of energetic electrons in the 20-200 keV range in the solar wind and of high speed solar wind streams with relativistic electrons in the magnetosphere to determine whether energetic electrons in the solar wind are the source of the outer relativistic electron radiation belt. Though there is some correlation between energetic electron enhancements in the solar wind and enhancements in the outer radiation belt, the phase space density of 20-200 keV electrons in the solar wind is not adequate to supply the outer radiation belt electrons. Although lower energy electrons in the solar wind could be a seed population of the outer radiation belt, such lower energy electrons cannot achieve relativistic energies through the normal process of radial transport which conserves the first adiabatic invariant. Thus additional internal acceleration processes are required within the magnetosphere to produce the outer radiation belt }, keywords={ electrons radiation belts solar wind energetic electrons WIND SAMPEX LANL sensor geostationary satellites high speed solar wind streams relativistic electrons magnetosphere outer relativistic electron radiation belt phase space density outer radiation belt electrons radial transport internal acceleration processes 20 to 200 keV }, mynotes={UNREAD}, } @ARTICLE{NakamuraMay95, author={Nakamura, R. and Baker, D.N. and Blake, J.B. and Kanekal, S. and Klecher, B. and Hovestadt, D.}, title={ Relativistic electron precipitation enhancements near the outer edge of the radiation belt }, journal={Geophysical Research Letters}, volume={22}, number={9}, year={1995}, month={May}, pages={1129-32}, abstract={ The authors examined characteristics of relativistic electron precipitation bursts observed by the Heavy Ion Large Telescope (HILT) experiment onboard the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) satellite. They report on relatively narrow, persistent, latitudinal bands of precipitation with time scales of 10 approximately 30 sec near the outer edge of the radiation belt; these develop and decay with a time scale of a few hours. Acceleration processes more effective than the usual radial diffusion process or scattering process would be needed to explain this strong precipitation band phenomenon. Another prominent signature is microbursts with a time scale down to a few hundred milliseconds. It is suggested that these microbursts are due to wave-particle interaction involving a relaxation-oscillator type of mechanism }, keywords={ atmospheric electron precipitation radiation belts magnetosphere HILT SAMPEX acceleration process enhancements outer edge radiation belt relativistic electron precipitation bursts latitudinal bands microbursts wave-particle interaction relaxation-oscillator type mechanism }, mynotes={UNREAD}, } @ARTICLE{HudsonFeb95, author={Hudson, M.K. and Kotelnikov, A.D. and Li, X. and Roth, I. and Temerin, M. and Wygant, J. and Blake, J.B. and Gussenhoven, M.S.}, title={ Simulation of proton radiation belt formation during the March 24, 1991 SSC }, journal={Geophysical Research Letters}, volume={22}, number={3}, year={1995}, month={Feb}, pages={291-4}, abstract={ The rapid formation of a new proton radiation belt at L approximately=2.5 following the March 24, 1991 storm sudden commencement (SSC) observed at the Combined Release and Radiation Effects Satellite (CRRES) is modelled using a relativistic guiding center test particle code. The SSC is modelled by a bipolar electric field and associated compression and relaxation in the magnetic field, superimposed on a dipole magnetic field. The source population consists of both solar and trapped inner zone protons. The simulations show that while both populations contribute to drift echoes in the 20-80 MeV range, primary contribution is from the solar protons. Proton acceleration by the SSC differs from relativistic electron acceleration in that different source populations contribute and nonrelativistic conservation of the first adiabatic invariant leads to greater energization of protons for a given decrease in L. Model drift echoes and flux distribution in L at the time of injection compare well with CRRES observations }, keywords={ magnetic storms protons radiation belts proton radiation belt formation simulation AD 1991 03 24 storm sudden commencement SSC Combined Release and Radiation Effects Satellite CRRES relativistic guiding centre test particle code bipolar electric field magnetic field compression magnetic field relaxation dipole magnetic field magnetosphere trapped inner zone protons drift echoes solar protons proton acceleration relativistic electron acceleration source populations nonrelativistic conservation first adiabatic invariant proton energization proton injection 20 to 80 MeV }, mynotes={UNREAD}, } @ARTICLE{BakerMar94, author={Baker, D.N. and Blake, J.B. and Callis, L.B. and Cummings, J.R. and Hovestadt, D. and Kanekal, S. and Klecker, B. and Mewaldt, R.A. and Zwickl, R.D.}, title={ Relativistic electron acceleration and decay time scales in the inner and outer radiation belts: SAMPEX }, journal={Geophysical Research Letters}, volume={21}, number={6}, year={1994}, month={Mar}, pages={409-12}, abstract={ High-energy electrons have been measured systematically in a low-altitude (520*675 km), nearly polar (inclination=82 degrees ) orbit. Count rate channels with electron energy thresholds ranging from 0.4 MeV to 3.5 MeV have been used to examine relativistic electron variations as a function of L-shell parameter and time. A long run of essentially continuous data (July 1992-July 1993) shows substantial acceleration of energetic electrons throughout much of the magnetosphere on rapid time scales. This acceleration appears to be due to solar wind velocity enhancements and is surprisingly large in that the radiation belt 'slot' region is often temporarily filled and electron fluxes are strongly enhanced even at very low L-values (L approximately 2). A superposed epoch analysis shows that electron fluxes rise rapidly for 2.51 MeV electron event in late March 1996 appears to have contributed significantly to a major spacecraft (Anik El) operational failure }, keywords={ magnetic storms magnetosphere radiation belts radiation belt AD 1996 recurrent magnetic storm recurrent geomagnetic storm relativistic electron enhancement outer magnetosphere ISTP coordinated measurements solar minimum conditions relativistic electron flux outer radiation zone high-speed solar wind stream high-speed stream }, mynotes={UNREAD}, } @ARTICLE{Xinlin-LiJul97, author={Xinlin Li, Baker and D.N., Temerin and M., Cayton and T.E., Reeves and E.G.D., Christensen and R.A., Blake and J.B., Looper and M.D., Nakamura and R. and Kanekal, S.G.}, title={ Multisatellite observations of the outer zone electron variation during the November 3-4, 1993, magnetic storm }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14123-40}, abstract={ The disappearance and reappearance of outer zone energetic electrons during the November 3-4, 1993, magnetic storm is examined utilizing data from the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), the Global Positioning System (GPS) series, and the Los Alamos National Laboratory (LANL) sensors onboard geosynchronous satellites. The relativistic electron flux drops during the main phase of the magnetic storm in association with the large negative interplanetary B/sub z/ and rapid solar wind pressure increase late on November 3. Outer zone electrons with E>3 MeV measured by SAMPEX disappear for over 12 hours at the beginning of November 4. This represents a 3 orders of magnitude decrease down to the cosmic ray background of the detector. GPS and LANL sensors show similar effects, confirming that the flux drop of the energetic electrons occurs near the magnetic equator and at all pitch angles. Enhanced electron precipitation was measured by SAMPEX at L>or=3.5. The outer zone electron fluxes then recover and exceed prestorm levels within one day of the storm onset and the inner boundary of the outer zone moves inward to smaller L (<3). These multiple-satellite measurements provide a data set which is examined in detail and used to determine the mechanisms contributing to the loss and recovery of the outer zone electron flux. The loss of the inner part of the outer zone electrons is partly due to the adiabatic effects associated with the decrease of Dst, while the loss of most of the outer part (those electrons initially at L>or=4.0) are due to either precipitation into the atmosphere or drift to the magnetopause because of the strong compression of the magnetosphere by the solar wind. The recovery of the energetic electron flux is due to the adiabatic effects associated with the increase in Dst, and at lower energies (<0.5 MeV) due to rapid radial diffusion driven by the strong magnetic activity during the recovery phase of the storm. Heating of the e }, keywords={ magnetic storms magnetosphere radiation belts magnetosphere radiation belt AD 1993 11 03 AD 1993 11 04 outer zone electron variation magnetic storm energetic electrons SAMPEX GPS relativistic electron flux decrease enhanced electron precipitation radial diffusion }, mynotes={UNREAD}, } @ARTICLE{KorthJul97, author={Korth, A. and Friedel, R.H.W.}, title={ Dynamics of energetic ions and electrons between L=2.5 and L=7 during magnetic storms }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14113-22}, abstract={ The variation of energetic electron and ion fluxes with L values between 2.5 and 7 as measured by two magnetic spectrometers (medium electrons A and B, MEA and MEB) on CRRES is presented for one intense and two weak magnetic storms, paying particular attention to the rate of accompanying substorms. Electrons in the energy range 45-602 keV and ions in the range 77-703 keV are examined. The data are presented in cuts through L versus time plots which are ideal to demonstrate the global aspect and the long-term variations of a magnetic storm in the outer radiation belt. The time resolution is half an orbital period of CRRES (5.5 hours). Substantial decreases and enhancements of electron and ion intensity are seen at the beginning and recovery of intense magnetic storms (Dst<-100 nT). Electrons and ions are shifted to lower L values during these storms and the slot region narrows for ions. The slot region can disappear completely for electrons during the recovery of the storm. For small magnetic storms (Dst about -30 nT), which seem to be caused by a series of substorms, the ring current does not move to lower L values and stays at L values of about 5.5 but weakens, even though Dst decreases. This is attributed to the strong substorm current systems. Knowledge of the past history of the radiation belts is required to separate "true" storm time depressions of Dst from substorm-related effects }, keywords={ magnetic storms radiation belts energetic ions energetic electrons magnetic storms fluxes substorm CRRES data intensity slot region recovery ring current current systems radiation belts Dst 45 to 703 keV }, mynotes={UNREAD}, } @ARTICLE{HudsonJul97, author={Hudson, M.K. and Elkington, S.R. and Lyon, J.G. and Marchenko, V.A. and Roth, I. and Temerin, M. and Blake, J.B. and Gussenhoven, M.S. and Wygant, J.R.}, title={ Simulations of radiation belt formation during storm sudden commencements }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14087-102}, abstract={ MHD fields from a global three-dimensional simulation of the great March 24, 1991, storm sudden commencement (SSC) are used to follow the trajectories of particles in a guiding center test particle simulation of radiation belt formation during this event. Modeling of less intense events during the lifetime of the CRRES satellite, with similar morphology but less radial transport and energization, is also presented. In all cases analyzed, a solar proton event was followed by an SSC, leading to the formation of a new proton belt earthward of solar proton penetration. The effect on particle energization of varying solar wind and model pulse parameters is investigated. Both a seed population of solar protons and the SSC shock-induced compression of the magnetosphere are necessary conditions for the formation of a new proton belt. The outer boundary of the inner zone protons can be affected by an SSC and a newly formed belt can be affected by the ensuing or a subsequent storm, which may occur in rapid succession, as was the case in June and July 1991. The acceleration process is effective for both northward and southward IMF, with more energization and inward radial transport for the southward case for otherwise comparable solar wind parameters, because of the initially more compressed magnetopause in the southward case. The inner boundary and stability of the newly formed belt depends on the magnitude of radial transport at the time of formation and subsequent ring current perturbation of adiabatic trapping }, keywords={ magnetic storms radiation belts radiation belt formation storm sudden commencements MHD fields global three-dimensional simulation March 24 1991 CRRES satellite solar proton event proton belt particle energization shock-induced compression magnetosphere outer boundary acceleration process IMF magnetopause radial transport ring current perturbation AD 1991 03 24 }, mynotes={UNREAD}, } @ARTICLE{ZongJun97, author={Zong, Q.G. and Wilken, B. and Reeves, G.D. and Daglis, I.A. and Doke, T. and Iyemori, T. and Livi, S. and Maezawa, K. and Mukai, T. and Kokubun, S. and Pu, Z.Y. and Ullaland, S. and Woch, J. and Lepping, R. and Yamamoto, T.}, title={ Geotail observations of energetic ion species and magnetic field in plasmoid-like structures in the course of an isolated substorm event }, journal={Journal of Geophysical Research}, volume={102}, number={A6}, year={1997}, month={Jun}, pages={11409-28}, abstract={ On January 15, 1994, the ion spectrometer high energy particle-low energy particle detector (HEP-LD) on the Japanese spacecraft Geotail observed five quasi-periodic energetic ion bursts in the deep tail (X=-96 R/sub E/). These bursts were associated with plasmoid-like structures in the magnetic field components. In addition, three multiple TCR groups were identified in the interval. The observations in the distant tail occurred during a time interval of substorm activity which also produced multiple injections in the geosynchronous orbit region. The HEP-LD observations show that B/sub z/ bipolar plasmoid-like structures are associated with tailward flowing particle bursts. However, earthward flowing particle bursts are predominantly associated with bipolar signatures in B/sub y/. In addition, an oxygen burst was seen in the back of a plasmoid (postplasmoid) which showed both B/sub y/ and B/sub z/ bipolar magnetic field signatures. The oxygen burst lasted for 23 min, and the density ratio (O/H) reached 15% for the HEP-LD energy rang (in the same plasmoid, this ratio was approximately 1% before the oxygen burst). The oxygen burst exhibited a strong beam-like structure which occupied only 6\7% of the full solid angle (4 pi ). The authors suggest that energized oxygen ions of ionospheric origin travel downtail in the narrow postplasmoid-plasma sheet which trails the plasmoid. Furthermore, they suggest that the magnetosphere dissipated larger quantities of energy during this very intense substorm event by ejecting multiple relatively small plasmoids rather than through the formation and ejection of a single large plasmoid }, keywords={ magnetic storms magnetosphere magnetosphere magnetotail magnetic tail plasma flow plasmoid Geotail observations energetic ion species magnetic field plasmoid-like structure isolated substorm event magnetic storm AD 1994 01 15 quasi-periodic energetic ion burst deep tail tailward flowing particle burst 96 Earthradii }, mynotes={UNREAD}, } @ARTICLE{BourdarieDec96, author={Bourdarie, S. and Boscher, D. and Beutier, T. and Sauvaud, J.-A. and Blanc, M.}, title={ Magnetic storm modeling in the Earth's electron belt by the Salammbo code }, journal={Journal of Geophysical Research}, volume={101}, number={A12}, year={1996}, month={Dec}, pages={27171-6}, abstract={ The Salammbo code, which solves the three-dimensional phase-space diffusion equation for the electron radiation belt, was used to explain the dynamic conditions present during a geomagnetic storm. With a simple injection model, the authors have characterized the dynamic behaviour for relativistic electrons in the outer belt. The particles in the range 100 keV-500 keV are diffused throughout the belt, with a shape essentially dependent on the radial diffusion coefficients. Particles with higher energies are "created" by acceleration of slower particles near the plasmapause location. The calculated shape of the fluxes in an L versus time grid for the 1 MeV electrons looks globally like those measured aboard the CRRES satellite }, keywords={ electrons magnetic storms radiation belts Salammbo code magnetic storm modelling Earth 3D phase-space diffusion equation electron radiation belt geomagnetic storm injection model relativistic electron dynamics radial diffusion coefficients particle acceleration plasmapause electron fluxes 100 to 500 keV 1 MeV }, mynotes={UNREAD}, } @ARTICLE{ShiokawaSep96, author={Shiokawa, K. and Yumoto, K. and Meng, C.-I. and Reeves, G.}, title={ Broadband electrons observed by the DMSP satellites during storm-time substorms }, journal={Geophysical Research Letters}, volume={23}, number={18}, year={1996}, month={Sep}, pages={2529-32}, abstract={ Electrons that have intense broadband spectra, are found to precipitate in the equatorward part of the auroral oval. The electrons are observed by the DMSP satellites in association with particular substorms during the main phase of magnetic storms. Electron fluxes are drastically enhanced after the substorm onset at all the energies measured (32 eV to 30 keV) at magnetic latitudes lower than 60 degrees (L<4). The energy flux of the electrons exceeds 1.0*10/sup 13/ eV cm/sup -2/s/sup -1/sr/sup -1/. The intense electron precipitation lasts less than 1 h. These characteristics are significantly different from those seen in the central plasma sheet region. The authors suggest that an unknown energization mechanism of these electrons exists at the inner part of the plasma sheet at L<4 during these particular storm-time substorms }, keywords={ atmospheric electron precipitation magnetic storms magnetosphere radiation belts ionosphere magnetosphere radiation belt electron precipitation magnetic storm substorm broadband electrons DMSP satellite intense broadband spectra intense electron precipitation plasma sheet magnetotail 30 eV to 32 keV }, mynotes={UNREAD}, } @ARTICLE{SauvaudSep96, author={Sauvaud, J.A. and Beutier, T. and Delcourt, D.}, title={ On the origin of flux dropouts near geosynchronous orbit during the growth phase of substorms. 1. Betatron effects }, journal={Journal of Geophysical Research}, volume={101}, number={A9}, year={1996}, month={Sep}, pages={19911-19}, abstract={ We investigate the origin of the flux dropouts which are quasi-systematically observed during the growth phase of substorms near the earthward edge of the plasma sheet in the midnight sector. We focus on the transport of energetic (50-200 keV) near-equatorially trapped ions using single-particle trajectory codes with time-varying electric and magnetic fields. We show that energetic ions which drift against the electric field induced by the stretching of the inner tail magnetospheric field lines experience large betatron decelerations. By virtue of the Liouville theorem, these decelerations lead to prominent decrease of flux for energetic particles drifting around the Earth close to the synchronous orbit. The magnitudes of the computed flux variations are comparable to those measured near the equatorial plane at 6.6 R/sub E/. On this basis, we argue that betatron deceleration in the presence of an inductive electric field is a potential mechanism for the development of energetic particle flux dropouts. We show that this mechanism depends little upon the field variation model adopted. It reproduces well the essential features of flux variations during substorm growth phases for both ions and electrons }, keywords={ atmospheric electricity magnetic storms magnetosphere flux dropouts geosynchronous orbit growth phase substorms plasma sheet midnight sector near-equatorially trapped ions single-particle trajectory codes electric field betatron decelerations inductive electric field flux variations 50 to 200 keV 6.6 Earthradii }, mynotes={UNREAD}, } @ARTICLE{FriedelJun96, author={Friedel, R.H.W. and Korth, A. and Kremser, G.}, title={ Substorm onsets observed by CRRES: determination of energetic particle source regions }, journal={Journal of Geophysical Research}, volume={101}, number={A6}, year={1996}, month={Jun}, pages={13137-54}, abstract={ The authors examine data from the Electron/Proton Angle Spectrometer instrument, also known as Medium Energy B, flown on the CRRES satellite (July 1990 to August 1991). Because of its strongly eccentric orbit, CRRES can detect substorm onsets in the region L=4 to L=8, covering the time sectors 1600-0800 MLT. Substorm onsets which are virtually dispersionless in energy have commonly been associated with acceleration processes which occur in the immediate vicinity of the satellite. Data from CRRES show that such virtually dispersionless onsets can occur far in the inner magnetosphere down to L=4.3 and are distributed up to +or-5 hours around local magnetic midnight. Results from a statistical study are presented. The authors develop a method of using single-satellite measurements of near-dispersionless substorm onsets, together with the observed "drift echoes" of these injections, to establish a "source region" for the energetic particles observed at onset. This method is applied to electrons only. A database of model drift paths has been set up and is used to calculate the possible interceptions between drift paths of various energies from a source region with the satellite trajectory. The authors' results indicate that the source region can have a sharp boundary in MLT and can extend over several R/sub E/. For some events it is possible to deduce an outer radial limit for the injection region, favoring a more local substorm onset mechanism. Their modeling further shows that the injection and drift echo signature observed at the satellite is quite insensitive to the actual shape of the injection boundary }, keywords={ magnetic storms CRRES satellite observations substorm onset magnetic storm magnetosphere energetic particle source region AD 1990 AD 1991 inner magnetosphere electron drift path }, mynotes={UNREAD}, } @ARTICLE{Chao-LiuMar96, author={Chao Liu and Horwitz, J.L.}, title={ Formation of low-energy trapped and field-aligned ion distributions in substorm dipolarization events }, journal={Journal of Geophysical Research}, volume={101}, number={A3}, year={1996}, month={Mar}, pages={4991-5001}, abstract={ A dynamic semikinetic simulation is used to study the effect of substorm dipolarization events on low-energy thermal plasmas initially distributed isotropically along closed tailward stretched magnetic field lines in the middle magnetosphere. The temporal variation of the magnetic field during dipolarization induces a perpendicular electric field that leads to E*B drift and produces centrifugal and betatron ion acceleration. The authors find that the dipolarization process produces field-aligned ion streams split into components with higher and lower speeds, as generated by parallel forces identified here as the "centrifugal force" and the "Coriolis force". The higher-speed component leads to ion precipitation which is highly dispersed in energy during the dipolarization event. The postdipolarization evolution of the lower-speed component produces energy-time spectrogram features similar to the "ion bounce clusters" observed at geosynchronous orbit and noted in the "convection surge" simulations of Mauk [1986]. An entirely new feature not found in previous dipolarization simulations is the formation of an equatorially trapped population whose flux is strongly peaked at the 90 degrees pitch angle and whose overall level sharply declines at latitudinal boundaries within 5 degrees of the equator. These equatorially trapped ion distributions are generated through the combined influence of equatorial focusing by the parallel centrifugal force and betatron perpendicular energization. The postdipolarization latitudinal density distributions contain a local maximum, due to the trapped ion population, at the equator, where the electric potential similarly contains a small peak. Hence the substorm dipolarization process provides a new, heretofore unrecognized mechanism for producing the characteristic equatorially trapped warm ion populations observed, for example, by Horwitz and Chappell [1979] and Olsen et al. [1987] }, keywords={ magnetic storms radiation belts trapped particles radiation belt low-energy trapped ion formation magnetosphere field-aligned ion distribution substorm dipolarization event magnetic storm dynamic semikinetic simulation low-energy thermal plasma closed tailward stretched magnetic field lines temporal variation betatron ion acceleration centrifugal ion acceleration field-aligned ion stream ion precipitation ion bounce cluster equatorially trapped warm ion populations }, mynotes={UNREAD}, } @ARTICLE{BeutierAug95, author={Beutier, T. and Boscher, D.}, title={ A three-dimensional analysis of the electron radiation belt by the Salammbo code }, journal={Journal of Geophysical Research}, volume={100}, number={A8}, year={1995}, month={Aug}, pages={14853-61}, abstract={ Using diffusion theory, the first results for a phase space three-dimensional model of the electron radiation belt are presented. The model is based on the numerical solution of a diffusion equation which takes into account the deceleration of electrons by free and bounded thermospheric and ionospheric electrons, pitch angle diffusion by Coulomb and wave-particle interactions and radial diffusion by magnetic and electric field perturbations. Sources of two types are included. Alone, the cosmic ray albedo neutron decay (CRAND) internal source gives results much lower than measured values, though with the addition of an external source, the orders of magnitude for the fluxes are reasonable, suggesting that the belt is created and maintained by the injections occurring during storms and substorms }, keywords={ electrons radiation belts phase space 3D model electron radiation belt Salammbo code numerical solution diffusion equation electron deceleration thermospheric electrons ionospheric electrons pitch angle diffusion Coulomb interactions wave-particle interactions radial diffusion magnetic field perturbations electric field perturbations cosmic ray albedo neutron decay CRAND internal source external source magnetic storm time electron injection magnetic substorms magnetosphere }, mynotes={UNREAD}, } @ARTICLE{MoldwinMay95, author={Moldwin, M.B. and Thomsen, M.F. and Bame, S.J. and McComas, D.J. and Birn, J. and Reeves, G.D. and Nemzek, R. and Belian, R.D.}, title={ Flux dropouts of plasma and energetic particles at geosynchronous orbit during large geomagnetic storms: entry into the lobes }, journal={Journal of Geophysical Research}, volume={100}, number={A5}, year={1995}, month={May}, pages={8031-43}, abstract={ Geosynchronous orbit spacecraft occasionally observe the magnetospheric tail lobe during disturbed geomagnetic conditions. These lobe intervals are characterized by an absence of detectable ion flux above 1 eV and an absence of electron flux above several hundred eV. This study is an extension of Thomsen et al. (1994) and examines geosynchronous orbit plasma measurements for lobe encounters during a 4-year period involving three spacecraft, for a total of 85 spacecraft-months of observations. During the interval surveyed, 160 lobe encounters or close encounters were observed. These events are divided into the following two classes: events observed near midnight and those observed along the flanks. Both classes of events were strongly associated with very active geomagnetic conditions as indicated by Kp (mean value of 5), Dst (mean value of -104 nT), and the Auroral Boundary Index, particularly the flank events. Fifty percent of the lobe encounters occurred within +or-24 hours of a geosynchronous magnetopause crossing, which indicates that many of the lobe encounters occurred when there was severe compression and/or erosion of the magnetosphere. Most of the magnetopause-crossing-associated events were flank events. The flank-lobe events were also generally associated with a large interplanetary magnetic field magnitude, with the B/sub y/ or B/sub z/ component being dominant. Dropouts in the energetic electron and ion fluxes were observed concurrently with the thermal ion plasma dropouts, though they often extended over a longer time interval. For most of the events a geosynchronous injection of energetic electrons and/or protons was observed following the beginning of the thermal ion dropout, often at a different satellite than the one observing the lobe. For a limited subset of the lobe events (17 events) in which a GOES satellite was nearby, the magnetic field data indicate that the field is often highly stretched or radial near the time of the lobe events. The aut }, keywords={ magnetic storms magnetosphere radiation belts magnetosphere flux dropout energetic particle plasma geosynchronous orbit synchronous orbit large geomagnetic storm magnetic storm entry into lobe flank-lobe event reconfiguration solar wind disturbance tail lobe }, mynotes={UNREAD}, } @ARTICLE{KorthJul94, author={Korth, A. and Vampola, A.L.}, title={ Cross-L motion of a relativistic electron belt formed in the slot region }, journal={Journal of Geophysical Research}, volume={99}, number={A7}, year={1994}, month={Jul}, pages={13529-35}, abstract={ A series of large magnetic storms during the March-June 1991 period produced major changes in energetic particle fluxes in the magnetosphere. The most significant change was the addition of a semidurable belt of extremely energetic particles (E/sub el/>15 MeV and E/sub prot/>40 MeV) at 2.26.5 MeV and >1 MeV respectively). Cross-L motion rates for the first week after the storm sudden commencement of March 24, for the first month, and for the next 6 months have been obtained. The long- and short-term average rates of motion across L, approximately 6*10/sup -4/ and approximately 3*10/sup -2/ per day at L=2.0 to 2.3, are similar to radial diffusion rates obtained from the distribution functions of fission electrons (Farley, 1969) and of relativistic electrons after a major magnetic storm (Tomassian et al., 1972). It is inferred from the constancy in width of the belt that radial diffusion proceeded predominantly toward lower L. The long-term apparent decay rate for the particle flux intensity as seen by these instruments is a simple exponential in time }, keywords={ magnetic storms radiation belts relativistic electron belt slot region large magnetic storms AD 1991 03 to 06 energetic particle fluxes magnetosphere semidurable belt CRRES data cross-L motion rates background effect storm sudden commencement radial diffusion apparent decay rate particle flux intensity 1 to 40 MeV }, mynotes={UNREAD}, } @ARTICLE{LiuFeb94, author={Liu, C. and Perez, J.D. and Moore, T.E. and Chappell, C.R.}, title={ Low energy particle signature of substorm dipolarization }, journal={Geophysical Research Letters}, volume={21}, number={3}, year={1994}, month={Feb}, pages={229-32}, abstract={ The low-energy particle signature of substorm dipolarization is exhibited through a case study of RIMS data on DE-1 at approximately 2100 MLT, ILAT=59 degrees approximately 65 degrees , L=3.8 approximately 5.4 R/sub E/, and geocentric distances 2.6 approximately 2.9 R/sub E/. A strong cross-field-line poleward outflow that lasts for a few minutes with a velocity that reaches at least 50 km/s is correlated with substorm activity evidenced in the AE index and the MAG-1 data. All the major species (H/sup +/, He/sup +/, O/sup +/) have the same bulk velocity. The parallel velocities are strongly correlated with the perpendicular velocities. The parallel acceleration results from the centrifugal force of the ExB drift induced by the dipolarizing perturbation of the magnetic field }, keywords={ atmospheric elementary particle precipitation atmospheric movements geomagnetic variations magnetic storms magnetosphere plasma geomagnetic field dipolarisation particle velocity cross-field-line poleward outflow duration plasmasphere AD 1981 10 20 charged particles bulk velocity magnetosphere plasma dynamics geomagnetic AE-index invariant latitude 59 degrees to 65 degrees inner magnetosphere substorm dipolarization low-energy particle signature RIMS data DE-1 substorm activity MAG-1 data parallel velocities perpendicular velocities centrifugal force ExB drift dipolarizing perturbation magnetic field 1 to 10 min 50 km/s 2.6 to 2.9 Earthradii H/sup +/ He/sup +/ O/sup +/ }, mynotes={UNREAD}, } @ARTICLE{Xinlin-LiNov93, author={Xinlin Li, Roth and I., Temerin and M., Wygant and J.R., Hudson and M.K. and Blake, J.B.}, title={ Simulation of the prompt energization and transport of radiation belt particles during the March 24, 1991 SSC }, journal={Geophysical Research Letters}, volume={20}, number={22}, year={1993}, month={Nov}, pages={2423-6}, abstract={ The authors model the rapid ( approximately 1 min) formation of a new electron radiation belt at L approximately=2.5 that resulted from the Storm Sudden Commencement (SSC) of March 24, 1991. The time-dependent magnetospheric electric field during the SSC is represented by an asymmetric bipolar pulse that is associated with the compression and relaxation of the Earth's magnetic field. The authors follow the electrons using a relativistic guiding center code. The test-particle simulations show that electrons with energies of a few MeV at L>6 were energized up to 40 MeV and transported to L approximately=2.5 during a fraction of their drift period. The energization process conserves the first adiabatic invariant and is enhanced as a result of the resonance of the electron drift motion with the time-varying electric field. The simulation results, with an initial W/sup -8/ energy flux spectrum, reproduce the observed electron drift echoes and show that the interplanetary shock impacted the magnetosphere between 1500 and 1800 MLT }, keywords={ atmospheric electricity atmospheric movements electrons interplanetary matter magnetic storms magnetosphere plasma radiation belts shock waves solar wind transport processes radiation belt electrons energisation electron energies radiation belt formation particles acceleration time particles transport geomagnetic field compression electron drift-electric field resonance electron drift period interplanetary shock-magnetosphere interaction geomagnetic field relaxation AD 1991 03 24 radiation belt particles March 24, 1991 SSC new electron radiation belt Storm Sudden Commencement time-dependent magnetospheric electric field asymmetric bipolar pulse relativistic guiding center code test-particle simulations first adiabatic invariant electron drift motion time-varying electric field initial W/sup -8/ energy flux spectrum electron drift echoes 40 MeV 2.5 Earthradii 6 Earthradii 60 s }, mynotes={UNREAD}, } @ARTICLE{EgelandFeb94, author={Egeland, A. and Burke, W.J. and Maynard, N.C. and Basinska, E.M. and Winningham, J.D. and Deehr, C.S.}, title={ Ground and satellite observations of postdawn aurorae near the time of a sudden storm commencement }, journal={Journal of Geophysical Research}, volume={99}, number={A2}, year={1994}, month={Feb}, pages={2095-108}, abstract={ Meridian scanning photometer measurements taken in the magnetic postdawn sector at Longyearbyen, Svalbard, between 0300 and 0630 UT on December 29, 1981, are analyzed in conjunction with particle and field data retrieved during two near passes of the DE 2 satellite. The interval included a sudden storm commencement (SSC). Pre-SSC optical and particle measurements showed a system of arcs that are spaced at approximately 1.1 degrees intervals in magnetic latitude, embedded within the region 1 current system and span the convection reversal. The softer particle precipitation appears to have a source near the flanks of the magnetotail while the harder, more equatorward precipitation originates closer to Earth. During the SSC period the entire sky brightened, with enhanced 630.0-nm emissions extending from the northern horizon to south of magnetic zenith; intense but spatially separated 557.7-nm emissions dominated the southern horizon. DE 2 detected a more than an order of magnitude increase and near isotropization of ring current electron fluxes, enhanced precipitation from the plasma sheet and significantly decreased auroral zone convection. Region 1/region 2 currents remained, with wavelike structures superposed. On few minute travel timescales for hydromagnetic waves to pass through the system, magnetospheric particles accelerate and precipitate to increase the ionospheric conductivity. Global, field-aligned currents change more slowly. To maintain similar field-aligned currents with higher ionospheric conductances requires reduced electric fields. After 0520 UT the optical emissions settled into stable, but latitudinally separated, bands of 630.0- and 557.7-nm emissions }, keywords={ atmospheric electricity atmospheric elementary particle precipitation aurora magnetic storms magnetosphere postdawn aurorae sudden storm commencement satellite observations meridian scanning photometer measurements magnetic postdawn sector DE 2 satellite arcs region 1 current system convection reversal particle precipitation magnetotail ring current electron fluxes plasma sheet auroral zone convection region 2 currents wavelike structures hydromagnetic waves magnetospheric particles ionospheric conductivity field-aligned currents optical emissions AD 1981 12 29 557.7 nm 630.0 nm }, mynotes={UNREAD}, } @ARTICLE{SanchezApr93, author={Sanchez, E.R. and Mauk, B.H. and Newell, P.T. and Meng, C.-I.}, title={ Low-altitude observations of the evolution of substorm injection boundaries }, journal={Journal of Geophysical Research}, volume={98}, number={A4}, year={1993}, month={Apr}, pages={5815-38}, abstract={ Analyzes the properties of the evolution of the ion and electron precipitation and the magnetic field perturbations in the auroral oval during substorms using the low-altitude polar-orbiting satellites DMSP F6 and F7. The authors show two examples where the magnetosphere-ionosphere coupling, based on the character of the particle precipitation and field-aligned current regions, exhibits different substorm responses. The main difference in the coupling response is reflected in the intensification of the ion keV plasma sheet precipitation flux }, keywords={ atmospheric electron precipitation atmospheric ion precipitation ionosphere magnetic storms DMSP F7 observations evolution substorm injection boundaries electron precipitation magnetic field perturbations auroral oval low-altitude polar-orbiting satellites DMSP F6 magnetosphere-ionosphere coupling field-aligned current regions substorm responses intensification ion keV plasma sheet precipitation flux }, mynotes={UNREAD}, } @ARTICLE{ShiokawaFeb93, author={Shiokawa, K. and Yumoto, K.}, title={ Global characteristics of particle precipitation and field-aligned electron acceleration during isolation substorms }, journal={Journal of Geophysical Research}, volume={98}, number={A2}, year={1993}, month={Feb}, pages={1359-75}, abstract={ The authors select typical isolated substorms using both low-latitude Pi 2 magnetic pulsations and the AU and AL indices. For the selected substorms, they analyze precipitating electron and ion data obtained by the DMSP F6 and F7 satellites at ionospheric altitudes. Global characteristics of particle precipitation and field-aligned electron acceleration processes are discussed in terms of the substorm time, i.e., before the substorm onset and during the recovery phase }, keywords={ atmospheric elementary particle precipitation magnetic storms magnetosphere magnetic substorm particle precipitation field-aligned electron acceleration isolation substorms }, mynotes={UNREAD}, } @ARTICLE{PulkkinenDec92, author={Pulkkinen, T.I. and Baker, D.N. and Pellinen, R.J. and Buchner, J. and Koskinen, H.E.J. and Lopez, R.E. and Dyson, R.L. and Frank, L.A.}, title={ Particle scattering and current sheet stability in the geomagnetic tail during the substorm growth phase }, journal={Journal of Geophysical Research}, volume={97}, number={A12}, year={1992}, month={Dec}, pages={19283-97}, abstract={ The degree of pitch angle scattering and chaotization of various particle populations in the geomagnetic tail during the substorm growth phase is studied by utilizing the Tsyganenko 1989 magnetic field model. A temporally evolving magnetic field model for the growth phase is constructed by enhancing the near-Earth currents and thinning the current sheet from the values given by the static Tsyganenko model. Changing the field geometry toward an increasingly taillike configuration leads to pitch angle scattering of particles whose Larmor radii become comparable to the field line radius of curvature. Several different cases representing substorms with varying levels of magnetic disturbance have been studied. In each case, the field development during the growth phase leads to considerable scattering of the thermal electrons relatively close to the Earth }, keywords={ magnetic storms magnetosphere magnetic tail magnetotail Earth magnetosphere particle scattering plasma instability magnetic storm current sheet stability geomagnetic tail substorm growth phase pitch angle scattering chaotization particle populations magnetic field model Tsyganenko model Larmor radii }, mynotes={UNREAD}, } @ARTICLE{ChenMar92, author={Chen, M.W. and Schulz, M. and Lyons, L.R. and Gorney, D.J.}, title={ Ion radial diffusion in an electrostatic impulse model for stormtime ring current formation }, journal={Geophysical Research Letters}, volume={19}, number={6}, year={1992}, month={Mar}, pages={621-4}, abstract={ Guiding-center simulations of stormtime transport of ring-current and radiation-belt ions having first adiabatic invariants mu >or approximately= 15 MeV/G (E>or approximately=165 keV at L approximately 3) are surprisingly well described (typically within a factor of J/sub ///. As the satellite penetrates deeper into the plasma sheet, the spectrum further hardens, especially near alpha /sub 0/ approximately 90 degrees . At the injection the electron spectrum drastically hardens and often becomes peaked in the keV energy range. The pitch angle anisotropy is further enhanced in favor of J/sub perpendicular to /. The plasma wave emissions onset occurred as the time of the injection. Whistler mode waves are observed below the electron cyclotron frequency. Electrostatic waves are detected in bands between the electron cyclotron frequency harmonics }, keywords={ magnetosphere trapped particle magnetosphere AD 1979 substorm wave dynamics plasma injections plasmasphere plasma sheet plasma waves pitch angle anisotropy }, mynotes={UNREAD}, } @ARTICLE{KremserJun82, author={Kremser, G. and Bjordal, J. and Block, L.P. and Bronstad, K. and Havag, M. and Iversen, I.B. and Kangas, J. and Korth, A. and Madsen, M.M. and Niskanen, J. and Riedler, W. and Stadsnes, J. and Tanskanen, P. and Torkar, K.M. and Ullaland, S.L.}, title={ Coordinated balloon-satellite observations of energetic particles at the onset of a magnetospheric substorm }, journal={Journal of Geophysical Research}, volume={87}, number={A6}, year={1982}, month={Jun}, pages={4445-53}, abstract={ Coordinated observations of electron precipitation via X-ray measurements from three simultaneously flown balloons, and of energetic particles at the geosynchronous satellite GEOS 2, were used to investigate variations of the distribution of energetic charged particles at the onset of a magnetospheric substorm on July 3, 1979. It is concluded that the electron precipitation was directly related to the injection of electrons and that the injection took place well earthward of the near-Earth reconnection region postulated in some substorm models. A possible mechanism that would connect injection to reconnection is proposed. The influence of parallel electric fields on the particle distribution is discussed }, keywords={ atmospheric electron precipitation magnetic storms magnetosphere trapped particle magnetosphere magnetic storm AD 1979 07 03 energetic particles onset substorm electron precipitation variations injection reconnection }, mynotes={UNREAD}, } @ARTICLE{NagaiMay82, title={ Local time dependence of electron flux changes during substorms derived from multi-satellite observation at synchronous orbit }, journal={Journal of Geophysical Research}, volume={87}, number={A5}, year={1982}, month={May}, pages={3456-68}, abstract={ Energetic electron (energy higher than 2 MeV) observations by a synchronous satellite chain covering the local time extent of approximately 10 hr have been used to study the large-scale characteristics of the dynamic behavior in the Near-earth magnetosphere for substorms, in which low-latitude positive bay aspects are clearly seen in the ground magnetic data. Simultaneous multi-satellite observations have clearly demonstrated the local time dependence of electron flux changes during substorms and the longitudinal extent of electron flux variations. A detailed description of the electron flux changes is given }, keywords={ magnetic storms magnetosphere substorm local time dependence trapped particle electron flux changes local time magnetosphere bay longitudinal variations }, mynotes={UNREAD}, } @ARTICLE{ParkJan81, author={Park, C.G. and Lin, C.S. and Parks, G.K.}, title={ A ground-satellite study of wave-particle correlations }, journal={Journal of Geophysical Research}, volume={86}, number={A1}, year={1981}, month={Jan}, pages={37-53}, abstract={ Very low frequency (VLF) waves recorded at Siple, Antarctica (L approximately 4; 84 degrees W, geographic), are compared with low-energy (<50 keV) electron data from the geostationary satellite ATS 6. During the period of this study (August 10-21, 1974) the satellite was anchored at 6.6 R/sub E/ and 106.5 degrees W, near the outer edge of the nominal 'viewing area' of the Siple VLF receiver, which is estimated to be L approximately 2-6 and +or-20 degrees longitude. The results reveal two distinct types of chorus observed at Siple. One type is closely correlated with enhanced fluxes of >5-keV electrons detected at the synchronous altitude, and its generation region is inferred to be outside the plasmapause. The chorus upper cutoff frequency increases with time in a characteristic manner, consistent with the expected adiabatic motion of injected electrons in cyclotron resonance with the waves. The second type of chorus, which is referred to a 'plasmapheric chorus', occurs inside the plasmapause, has no apparent relationship to particle injection at the synchronous altitude and shows clear evidence of being triggered by whistlers, power line radiation, and other signals. The two different types of chorus are readily distinguishable in frequency-time spectrograms }, keywords={ atmospheric electron precipitation atmospheric radiation atmospherics magnetic storms magnetosphere Siple Antarctica geostationary satellite ATS 6 Siple VLF receiver chorus upper cutoff frequency plasmapheric chorus plasmapause particle injection synchronous altitude whistlers power line radiation frequency-time spectrograms magnetosphere chorus VLF atmospherics EM wave generation region magnetospheric substorms electrons-waves cyclotron resonance AD 1974 08 10 to 21 injected electrons adiabatic motion magnetic storms low energy electron fluxes }, mynotes={UNREAD}, } @ARTICLE{TsurutaniNov77, author={Tsurutani, B.T. and Smith, E.J.}, title={ Two types of magnetospheric ELF chorus and their substorm dependences }, journal={Journal of Geophysical Research}, volume={82}, number={32}, year={1977}, month={Nov}, pages={5112-28}, abstract={ Extremely low frequency (10-1500 Hz) magnetospheric chorus has been analyzed to investigate a possible dependence on substorms. Care was taken to separate spatial effects from temporal effects by analyzing an entire year of data acquired by the Ogo 5 search coil magnetometer. A major finding of the study of spatial dependences is that chorus occurs principally in two magnetic latitude regions. Equatorial chorus is detected near the equator, ahd high-latitude chorus is found at magnetic latitudes above 15 degrees . When chorus in these two regions is analyzed separately, substorm dependences become apparent. Comparisons with AE indicate that equatorial chorus occurs primarily during substorms. High-latitude chorus is not strongly dependent on AE. The dependence of equatorial chorus on local time, magnetic latitude, and L is consistent with generation by a cyclotron resonance between the whistler mode chorus and 10- to 100-keV trapped substorm electrons }, keywords={ atmospheric radiation atmospherics electrons magnetic storms magnetosphere magnetospheric ELF chorus Ogo 5 search coil magnetometer magnetic latitude regions local time magnetic latitude cyclotron resonance whistler mode chorus 10 to 1500 Hz chorus magnetic substorms L-value chorus spatial dependence equatorial chorus high latitude chorus AE-Geomagnetic index 10 to 100 keV trapped substorm electrons postmidnight sector minimum-B pockets }, mynotes={UNREAD}, } @ARTICLE{VanAllen59}, author={Van-Allen, J. A and McIlwain, C. E. and Ludwig, G. H.}, title={Radiation Observations with Satellite 1958e}, journal={Journal of Geophysical Research}, volume={64}, number={}, year={1959}, month={}, pages={271}, abstract={}, keywords={}, mynotes={UNREAD}, } @ARTICLE{Kennel66, author={Kennel, C. F and Petschek, H. E.}, title={Limits on stable trapped particle fluxes}, journal={Journal of Geophysical Research}, volume={71}, number={}, year={1966}, month={}, pages={1}, abstract={}, keywords={}, mynotes={UNREAD}, } @ARTICLE{LyonsJun77, title={ Adiabatic evolution of trapped particle pitch angle distributions during a storm main phase }, journal={Journal of Geophysical Research}, volume={82}, number={16}, year={1977}, month={Jun}, pages={2428-32}, abstract={ Equatorial pitch angle distributions of >2O0-keV ions obtained near L=4 by Explorer 45 during a storm main phase show the development of marked minima at 90 degrees pitch angle in direct association with a greater than a factor of 2 reduction in the equatorial magnetic field magnitude. The evolution of these pitch angle distributions can be quantitatively explained as a result of conservation of the first two adiabatic invariants provided the magnitude of the magnetic field decrease was approximately constant along field lines }, keywords={ ion density magnetic storms trapped particle pitch angle distributions storm main phase ions Explorer 45 magnetic storms }, mynotes={UNREAD}, } @ARTICLE{AndersonJan77, author={Anderson, R.R. and Maeda, K.}, title={ VLF emissions associated with enhanced magnetospheric electrons }, journal={Journal of Geophysical Research}, volume={82}, number={1}, year={1977}, month={Jan}, pages={135-46}, abstract={ During periods of geomagnetic disturbances, VLF emissions and enhancements of low-energy electrons are simultaneously observed by the equatorial orbiting S/sup 3/-A (Explorer 45) satellite. These events are characterized by the following features. The VLF emissions occur outside the plasmasphere in the nightside of the magnetosphere. The VLF emissions consist of two frequency regimes, one below the local electron gyrofrequency f/sub g/ and the other above f/sub g/. The VLF emissions below f/sub g/ are relatively broadband whistler mode waves characteristic of chorus and frequently have a conspicuous band of missing emissions near f/sub g//2. The emissions above f/sub g/ are electrostatic and typically have components near 3f/sub g//2. The onset of the emissions coincides with abrupt increases outside the plasmasphere in 1- to 10-keV electrons to intensities of the order of 10/sup 8/ el cm/sup -2/ s/sup -1/ sr/sup -1/ keV/sup -1/. These observed features indicate that the VLF emissions are produced by low-energy (1- to 10-keV) electrons which penetrate into the dusk-midnight sector of the magnetosphere from the geomagnetic tail during magnetic storms and substorms and drift eastward outside the plasmasphere }, keywords={ atmospheric electron precipitation magnetic storms magnetosphere magnetospheric electromagnetic wave propagation whistlers VLF emissions enhanced magnetospheric electrons geomagnetic disturbances frequency regimes local electron gyrofrequency broadband whistler mode waves chorus low energy electrons extraplasmasphere emissions nightside magnetosphere 1 to 10 keV electrons electrostatic emissions dusk to midnight sector magnetotail Explorer 45 satellite missing emissions band }, mynotes={UNREAD}, } @ARTICLE{ShiokawaJul97, author={Shiokawa, K. and Meng, C.-I. and Reeves, G.D. and Rich, F.J. and Yumoto, K.}, title={ A multievent study of broadband electrons observed by the DMSP satellites and their relation to red aurora observed at midlatitude stations }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14237-53}, abstract={ Broadband electrons during magnetic storms are characterized by an unusually intense flux of precipitating electrons in the broadband energy range from 30 eV to 30 keV near the equatorward edge of the auroral oval (47 degrees -66 degrees magnetic latitude). Broadband electrons were first reported by Shiokawa et al. [1996]. In this paper, the authors report a multievent study of broadband electrons, using particle data obtained by the Defense Meteorological Satellite Program (DMSP) satellites during 23 magnetic storms from January 1989 through May 1992. Twelve broadband electron events are identified. Most of them are observed in the night sector, but some are observed in the morning sector. Particle data for successive polar passes of the DMSP multisatellites are used to show that broadband electrons generally last for less than 30 min and that for some events, they precipitate over a wide range of local times simultaneously. On the basis of a quantitative calculation of optical emissions from electrons in the neutral atmosphere, the authors conclude that broadband electrons are a possible cause of red auroras observed at midlatitude ground stations. They suggest that broadband electrons are associated with certain substorms during the main phase of magnetic storms, This conjecture comes from observations of H component positive bays and Pi 2 pulsations observed at low-latitude magnetic stations and from magnetic field variations observed at geosynchronous satellites. They conclude that the magnetospheric source of broadband electrons lies within the inner part of the plasma sheet. This conclusion is based on the facts that broadband electrons appear in latitudes where plasma sheet particles were observed before the event and that broadband electrons are observed poleward of the subauroral ion drifts, a position that corresponds to the inner edge of the injected particle layer during storms. High-energy particle data obtained at geosynchronous satellites show that b }, keywords={ atmospheric electron precipitation aurora magnetosphere ionosphere magnetosphere electron precipitation multievent study broadband electrons DMSP red aurora middle latitude midlatitude magnetic storm equatorward edge auroral oval AD 1989 AD 1990 AD 1991 AD 1992 substorm magnetospheric source plasma sheet broadband electron production mechanism 30 eV to 30 keV }, mynotes={UNREAD}, } @ARTICLE{ShiokawaSep96, author={Shiokawa, K. and Yumoto, K. and Meng, C.-I. and Reeves, G.}, title={ Broadband electrons observed by the DMSP satellites during storm-time substorms }, journal={Geophysical Research Letters}, volume={23}, number={18}, year={1996}, month={Sep}, pages={2529-32}, abstract={ Electrons that have intense broadband spectra, are found to precipitate in the equatorward part of the auroral oval. The electrons are observed by the DMSP satellites in association with particular substorms during the main phase of magnetic storms. Electron fluxes are drastically enhanced after the substorm onset at all the energies measured (32 eV to 30 keV) at magnetic latitudes lower than 60 degrees (L<4). The energy flux of the electrons exceeds 1.0*10/sup 13/ eV cm/sup -2/s/sup -1/sr/sup -1/. The intense electron precipitation lasts less than 1 h. These characteristics are significantly different from those seen in the central plasma sheet region. The authors suggest that an unknown energization mechanism of these electrons exists at the inner part of the plasma sheet at L<4 during these particular storm-time substorms }, keywords={ atmospheric electron precipitation magnetic storms magnetosphere radiation belts ionosphere magnetosphere radiation belt electron precipitation magnetic storm substorm broadband electrons DMSP satellite intense broadband spectra intense electron precipitation plasma sheet magnetotail 30 eV to 32 keV }, mynotes={UNREAD}, } @ARTICLE{LoeweJul97, author={Loewe, C.A. and Prolss, G.W.}, title={ Classification and mean behavior of magnetic storms }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14209-13}, abstract={ The Dst index is used to identify more than 1000 storms which occurred in the time interval 1957 to 1993. Using the minimum Dst value as an indicator, the authors classify the storms as weak (482), moderate (346), strong (206), severe (45), and great (6). For each of these classes the mean time variation is determined. In contrast to the well-known study of Sugiura and Chapman [1960], the Dst minimum is used as a common reference epoch. This leads to much better agreement between the average and the typical storm behavior. The authors also find that the maximum ap and AE activity precedes the Dst minimum by 1 to 2 hours. Finally, they demonstrate that both sudden commencement and gradual commencement storms are associated with a distinct decrease in the B/sub z/ component of the interplanetary magnetic field }, keywords={ magnetic storms magnetosphere classification strength magnetic storm mean behavior Dst index AD 1957 to 1993 weak storm moderate storm strong storm severe storm great storm class mean time variation AE activity ap activity storm sudden commencement SSC gradual commencement interplanetary magnetic field IMF direction IMF decrease }, mynotes={UNREAD}, } @ARTICLE{HudsonJul97, author={Hudson, M.K. and Elkington, S.R. and Lyon, J.G. and Marchenko, V.A. and Roth, I. and Temerin, M. and Blake, J.B. and Gussenhoven, M.S. and Wygant, J.R.}, title={ Simulations of radiation belt formation during storm sudden commencements }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14087-102}, abstract={ MHD fields from a global three-dimensional simulation of the great March 24, 1991, storm sudden commencement (SSC) are used to follow the trajectories of particles in a guiding center test particle simulation of radiation belt formation during this event. Modeling of less intense events during the lifetime of the CRRES satellite, with similar morphology but less radial transport and energization, is also presented. In all cases analyzed, a solar proton event was followed by an SSC, leading to the formation of a new proton belt earthward of solar proton penetration. The effect on particle energization of varying solar wind and model pulse parameters is investigated. Both a seed population of solar protons and the SSC shock-induced compression of the magnetosphere are necessary conditions for the formation of a new proton belt. The outer boundary of the inner zone protons can be affected by an SSC and a newly formed belt can be affected by the ensuing or a subsequent storm, which may occur in rapid succession, as was the case in June and July 1991. The acceleration process is effective for both northward and southward IMF, with more energization and inward radial transport for the southward case for otherwise comparable solar wind parameters, because of the initially more compressed magnetopause in the southward case. The inner boundary and stability of the newly formed belt depends on the magnitude of radial transport at the time of formation and subsequent ring current perturbation of adiabatic trapping }, keywords={ magnetic storms radiation belts radiation belt formation storm sudden commencements MHD fields global three-dimensional simulation March 24 1991 CRRES satellite solar proton event proton belt particle energization shock-induced compression magnetosphere outer boundary acceleration process IMF magnetopause radial transport ring current perturbation AD 1991 03 24 }, mynotes={UNREAD}, } @ARTICLE{ArakiJul97, author={Araki, T. and Fujitani, S. and Emoto, M. and Yumoto, K. and Shiokawa, K. and Ichinose, T. and Luehr, H. and Orr, D. and Milling, D.K. and Singer, H. and Rostoker, G. and Tsunomura, S. and Yamada, Y. and Liu, C.F.}, title={ Anomalous sudden commencement on March 24, 1991 }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14075-86}, abstract={ An anomalous geomagnetic sudden commencement (SC) occurred on March 24, 1991. It is characterized by an exceptionally large and sharp impulse observed in its initial part along the noon meridian in middle and low latitudes. The analysis of the SC was made by using high time resolution digital data from the 210 degrees Meridian Magnetometer Chain in the west Pacific, Sub-Auroral Magnetometer Network (SAMNET) in the United Kingdom and southern Scandinavia, the EISCAT Magnetometer Cross in northern Scandinavia and Svalbard, and Canopus in Canada together with other ground and satellite (GOES 6, GOES 7, CRRES, and GMS) data. The results of the analysis suggest that the pulse observed at lower-latitude ground stations was caused by the propagation of a strong magnetospheric compression of short duration (less than 1 min) which has never been observed before this event. The HF Doppler observation in Kyoto near local noon seems to be consistent with existence of the bipolar electric field associated with the propagating compressional magnetic pulse. The SAMNET stations and CRRES in the early morning also detected positive pulses which delays 30-50 s from the pulses in noon sector. Although the delay in the peak time of the pulse observed on the ground is consistent with ionospheric hydromagnetic wave propagation from the dayside to the nightside with finite speed, the initial onset time of the pulse on the ground was almost simultaneous everywhere suggesting the existence of an "almost instantaneous" propagation mode below the ionosphere }, keywords={ ionospheric disturbances magnetic storms plasma waves anomalous sudden commencement March 24 1991 geomagnetic sudden commencement noon meridian strong magnetospheric compression bipolar electric field propagating compressional magnetic pulse ionospheric hydromagnetic wave propagation dayside nightside AD 1991 03 24 }, mynotes={UNREAD}, } @ARTICLE{GrandeNov96, author={Grande, M. and Perry, C.H. and Blake, J.B. and Chen, M.W. and Fennell, J.F. and Wilken, B.}, title={ Observations of iron, silicon, and other heavy ions in the geostationary altitude region during late March 1991 }, journal={Journal of Geophysical Research}, volume={101}, number={A11}, year={1996}, month={Nov}, pages={24707-18}, abstract={ Following the great sudden storm commencement of March 24, 1991, observations were made aboard CRRES of Fe, Mg, Si, and other heavy ions in the energy range of several tens to a few hundred keV/n. The charge states of these heavy ions were observed to change abruptly. For example, the dominant Fe charge state changed at one point from q=9/sup +/ to q=16/sup +/. We suggest that ions from the solar corona, retaining the charge state frozen in near the Sun, were convected inward to the location of CRRES from the plasma sheet within minutes. The ions were energized in the convection process, and the ionic charge state was unaltered by charge exchange. The very large magnetospheric electric fields associated with the highly disturbed geomagnetic conditions were required to enable the ions to reach CRRES. Guiding center simulations were carried out which support this hypothesis. At least two ion populations were observed, corresponding to temperatures at two different coronal locations, and the observed changes in heavy-ion charge state were caused by a sequence of solar wind parcels sweeping over the Earth's magnetosphere. The signature of a change from low to high temperature seems to fit well the suggestions of Tsurutani and Gonzales [1994], of a fast solar wind stream tamped by a slower one, as a generator of great storms }, keywords={ atmospheric composition atmospheric electricity magnetosphere solar corona solar wind heavy ions geostationary altitude region great sudden storm commencement March 24 1991 CRRES charge states solar corona Sun plasma sheet convection process magnetospheric electric fields disturbed geomagnetic conditions ion population solar wind parcels temperature solar wind stream AD 1991 03 24 Fe Mg Si }, mynotes={UNREAD}, } @ARTICLE{ShumilovAug96, author={Shumilov, O. and Kasatkina, E. and Raspopov, O. and Hansen, T. and Frank-Kamenetsky, A.}, title={ Sudden-commencement-triggered pulsations at high latitudes and their sources in the magnetosphere }, journal={Journal of Geophysical Research}, volume={101}, number={A8}, year={1996}, month={Aug}, pages={17355-63}, abstract={ Sudden-commencement-associated geomagnetic pulsations have been studied using the magnetometer records from Mirny ( Phi '=-77.2 degrees ) and Heiss Island ( Phi '=74.1 degrees ) high-latitude observatories, where Phi ' is the corrected geomagnetic latitude. These pulsations have time delays from the onsets ranging between 4 and 22 min. Dominant periods of the pulsations observed lie in the range 20-50 s. The pulsations were accompanied by absorption events that are quite different from sudden commencement absorption and auroral absorption events observed earlier at high latitudes. The results of multifactoral analysis demonstrated that the solar wind speed is the most important parameter controlling the geomagnetic pulsation occurrence. It was assumed that a Kelvin-Helmholtz instability arising at some magnetospheric boundaries seems to be a more probable cause of the pulsations observed. The work gives further evidence to the results of Rostoker et al. [1984], and Conners and Rostoker [1993], who considered auroral and magnetic disturbances in the light of KHI development at some magnetospheric interfaces }, keywords={ micropulsations magnetic pulsation magnetosphere micropulsation sudden commencement triggered pulsation high latitude magnetospheric source geomagnetic pulsations Mirny Heiss Island time delays multifactoral analysis solar wind speed geomagnetic pulsation occurrence solar wind interaction Kelvin-Helmholtz instability plasma instability magnetospheric boundary }, mynotes={UNREAD}, } @ARTICLE{BuonsantoDec95, title={ A case study of the ionospheric storm dusk effect }, journal={Journal of Geophysical Research}, volume={100}, number={A12}, year={1995}, month={Dec}, pages={23857-69}, abstract={ The initial ionospheric storm positive phase often appears as a large enhancement in F region electron density at middle latitudes in the evening hours following a storm sudden commencement. The cause of this dusk effect is still not well understood, though several mechanisms have been proposed. This phenomenon is studied using incoherent scatter radar data collected at Millstone Hill and total electron content data from a north-south chain of stations during the May 26-27, 1990, storm. Nine-position Millstone Hill radar data allows estimation of gradients in electron density and in velocity components above the station. From these the motion term in the continuity equation is calculated and used along with wind, electric field data, and modeling to assess the relative importance of the proposed mechanisms during this storm. It is shown that a combination of mechanisms appear to have been involved, including a traveling atmospheric disturbance, advection of high-density plasma from lower latitudes, and neutral composition changes }, keywords={ atmospheric movements electron density F-region ionospheric disturbances ionospheric storm dusk effect positive phase F region electron density middle latitudes storm sudden commencement velocity components motion term continuity equation wind electric field traveling atmospheric disturbance advection high-density plasma neutral composition AD 1990 05 26 to 27 }, mynotes={UNREAD}, } @ARTICLE{McEwenOct95, author={McEwen, D.J. and Huang, K.}, title={ The polar onset and development of the November 8 and 9, 1991, global red aurora }, journal={Journal of Geophysical Research}, volume={100}, number={A10}, year={1995}, month={Oct}, pages={19585-94}, abstract={ On November 8, 1991, a major magnetic storm began with a sudden commencement at 0647 UT; it continued until about 1800 UT on November 9. Associated with this storm there was a great aurora which continued through November 8 and until at least 1200 UT on November 9. The first optical indication of this event was the appearance of bright Sun-aligned arcs over Eureka, North West Territories (89 degrees corrected geomagnetic latitude (CGM)), Canada from 0750 UT until about 1230 UT on November 8. By that time, there was a gradual transformation to dominant 6300 AA emission over the central polar cap. Gradually, the major soft electron precipitation and associated red aurora moved equatorward. The aurora reached a low-latitude limit of 40 degrees CGM at 0600 UT on November 9. The polar arcs reached 22 kR intensity (5577 AA), while the red aurora seen later at low latitudes was at least 100 kR (6300 AA). The analysis of Defense Meteorological Satellite Program (DMSP) particle data from 83 passes during November 8 and 9 showed the extent and movement of precipitation from the polar region to midlatitudes. A comparison of this event was made with the earlier great auroral event of March 13-14, 1989. While the extent in low latitude and the duration of the two disturbances were similar, the November 8-9 event had approximately one half of the total energy input into the ionosphere. Its striking and unusual feature was the auroral onset and activity in the central polar region, a feature possibly related to the solar wind interplanetary magnetic field orientation }, keywords={ aurora magnetic storms AD 1991 11 08 to 09 global red aurora polar onset development major magnetic storm sudden commencement bright Sun-aligned arcs central polar cap soft electron precipitation polar arcs Defense Meteorological Satellite Program DMSP particle data visible disturbances ionospheric energy input solar wind interplanetary magnetic field orientation 557.7 nm 630 nm O }, mynotes={UNREAD}, } @ARTICLE{HudsonFeb95, author={Hudson, M.K. and Kotelnikov, A.D. and Li, X. and Roth, I. and Temerin, M. and Wygant, J. and Blake, J.B. and Gussenhoven, M.S.}, title={ Simulation of proton radiation belt formation during the March 24, 1991 SSC }, journal={Geophysical Research Letters}, volume={22}, number={3}, year={1995}, month={Feb}, pages={291-4}, abstract={ The rapid formation of a new proton radiation belt at L approximately=2.5 following the March 24, 1991 storm sudden commencement (SSC) observed at the Combined Release and Radiation Effects Satellite (CRRES) is modelled using a relativistic guiding center test particle code. The SSC is modelled by a bipolar electric field and associated compression and relaxation in the magnetic field, superimposed on a dipole magnetic field. The source population consists of both solar and trapped inner zone protons. The simulations show that while both populations contribute to drift echoes in the 20-80 MeV range, primary contribution is from the solar protons. Proton acceleration by the SSC differs from relativistic electron acceleration in that different source populations contribute and nonrelativistic conservation of the first adiabatic invariant leads to greater energization of protons for a given decrease in L. Model drift echoes and flux distribution in L at the time of injection compare well with CRRES observations }, keywords={ magnetic storms protons radiation belts proton radiation belt formation simulation AD 1991 03 24 storm sudden commencement SSC Combined Release and Radiation Effects Satellite CRRES relativistic guiding centre test particle code bipolar electric field magnetic field compression magnetic field relaxation dipole magnetic field magnetosphere trapped inner zone protons drift echoes solar protons proton acceleration relativistic electron acceleration source populations nonrelativistic conservation first adiabatic invariant proton energization proton injection 20 to 80 MeV }, mynotes={UNREAD}, } @ARTICLE{WygantAug94, author={Wygant, J. and Mozer, F. and Temerin, M. and Blake, J. and Maynard, N. and Singer, H. and Smiddy, M.}, title={ Large amplitude electric and magnetic field signatures in the inner magnetosphere during injection of 15 MeV electron drift echoes }, journal={Geophysical Research Letters}, volume={21}, number={16}, year={1994}, month={Aug}, pages={1739-42}, abstract={ Electric and magnetic fields were measured by the CRRES spacecraft at an L-value of 2.2 to 2.6 near 0300 magnetic local time during a strong storm sudden commencement (SSC) on March 24, 1991. The electric field signature at the spacecraft at the time of the SSC was characterized by a large amplitude oscillation (80 mV/m peak to peak) with a period corresponding to the 150 second drift echo period of the simultaneously observed 15 MeV electrons. Considerations of previous statistical studies of the magnitude of SSC electric and magnetic fields versus local time and analysis of the energization and cross-L transport of the particles imply the existence of 200 to 300 mV/m electric fields over much of the dayside magnetosphere. These observations also suggest that the 15 MeV drift echo electrons were selectively energized because their gradient drift velocity allowed them to reside in the region of strong electric fields for the duration of the accelerating phase of the electric field }, keywords={ atmospheric electricity magnetic storms plasma radiation belts electric field signatures magnetic field signatures inner magnetosphere 15 MeV electron drift echoes CRRES spacecraft strong storm sudden commencement March 24 1991 drift echo period cross-L transport dayside gradient drift velocity accelerating phase AD 1991 03 24 15 MeV }, mynotes={UNREAD}, } @ARTICLE{KorthJul94, author={Korth, A. and Vampola, A.L.}, title={ Cross-L motion of a relativistic electron belt formed in the slot region }, journal={Journal of Geophysical Research}, volume={99}, number={A7}, year={1994}, month={Jul}, pages={13529-35}, abstract={ A series of large magnetic storms during the March-June 1991 period produced major changes in energetic particle fluxes in the magnetosphere. The most significant change was the addition of a semidurable belt of extremely energetic particles (E/sub el/>15 MeV and E/sub prot/>40 MeV) at 2.26.5 MeV and >1 MeV respectively). Cross-L motion rates for the first week after the storm sudden commencement of March 24, for the first month, and for the next 6 months have been obtained. The long- and short-term average rates of motion across L, approximately 6*10/sup -4/ and approximately 3*10/sup -2/ per day at L=2.0 to 2.3, are similar to radial diffusion rates obtained from the distribution functions of fission electrons (Farley, 1969) and of relativistic electrons after a major magnetic storm (Tomassian et al., 1972). It is inferred from the constancy in width of the belt that radial diffusion proceeded predominantly toward lower L. The long-term apparent decay rate for the particle flux intensity as seen by these instruments is a simple exponential in time }, keywords={ magnetic storms radiation belts relativistic electron belt slot region large magnetic storms AD 1991 03 to 06 energetic particle fluxes magnetosphere semidurable belt CRRES data cross-L motion rates background effect storm sudden commencement radial diffusion apparent decay rate particle flux intensity 1 to 40 MeV }, mynotes={UNREAD}, } @ARTICLE{YehApr94, author={Yeh, K.C. and Ma, S.Y. and Lin, K.H. and Conkright, R.O.}, title={ Global ionospheric effects of the October 1989 geomagnetic storm }, journal={Journal of Geophysical Research}, volume={99}, number={A4}, year={1994}, month={Apr}, pages={6201-18}, abstract={ Based on a large data base from 40 ionosonde stations distributed worldwide and 12 total electron content stations, a case study is made on the global behavior of ionospheric responses to the great magnetic storm of October 1989. The magnetic storm was triggered by a solar flare with the largest class of X13/4B and started with a sudden storm commencement (ssc) at 0917 UT on October 20. After the initial phase the storm underwent two periods of maximum activities in the following 2 days. Low-latitude auroras were sighted and reported in widely separated areas in both northern and southern hemispheres. In response to these magnetic and auroral activities the ionosphere showed remarkable effects. Depending on the local time of ssc occurrence, the ionospheric response differed appreciably. Impressive changes were long-lasting, large-scale effects, such as the severe depressions of foF2 at higher latitudes, the temporary suppression of the equatorial anomaly and large horizontal gradients at certain latitudes. Also observed were positive storm effects of short duration during the post-sunset period in response to the onset of both ssc and main phase of the magnetic storm. These two positive storm effects showed different patterns suggesting different causal mechanisms. In addition, global propagation of large-scale traveling ionospheric disturbances (TIDs) was seen during 2 nights, identified by dramatic rises of h'F with periodic fluctuations }, keywords={ ionosphere magnetic storms AD 1989 10 ionosphere disturbance global effect magnetic storm geomagnetic storm sudden storm commencement ssc SSC ionospheric response severe depression low latitude aurora F-region critical frequency equatorial anomaly travelling ionospheric disturbance traveling ionospheric disturbance TID }, mynotes={UNREAD}, } @ARTICLE{Xinlin-LiNov93, author={Xinlin Li, Roth and I., Temerin and M., Wygant and J.R., Hudson and M.K. and Blake, J.B.}, title={ Simulation of the prompt energization and transport of radiation belt particles during the March 24, 1991 SSC }, journal={Geophysical Research Letters}, volume={20}, number={22}, year={1993}, month={Nov}, pages={2423-6}, abstract={ The authors model the rapid ( approximately 1 min) formation of a new electron radiation belt at L approximately=2.5 that resulted from the Storm Sudden Commencement (SSC) of March 24, 1991. The time-dependent magnetospheric electric field during the SSC is represented by an asymmetric bipolar pulse that is associated with the compression and relaxation of the Earth's magnetic field. The authors follow the electrons using a relativistic guiding center code. The test-particle simulations show that electrons with energies of a few MeV at L>6 were energized up to 40 MeV and transported to L approximately=2.5 during a fraction of their drift period. The energization process conserves the first adiabatic invariant and is enhanced as a result of the resonance of the electron drift motion with the time-varying electric field. The simulation results, with an initial W/sup -8/ energy flux spectrum, reproduce the observed electron drift echoes and show that the interplanetary shock impacted the magnetosphere between 1500 and 1800 MLT }, keywords={ atmospheric electricity atmospheric movements electrons interplanetary matter magnetic storms magnetosphere plasma radiation belts shock waves solar wind transport processes radiation belt electrons energisation electron energies radiation belt formation particles acceleration time particles transport geomagnetic field compression electron drift-electric field resonance electron drift period interplanetary shock-magnetosphere interaction geomagnetic field relaxation AD 1991 03 24 radiation belt particles March 24, 1991 SSC new electron radiation belt Storm Sudden Commencement time-dependent magnetospheric electric field asymmetric bipolar pulse relativistic guiding center code test-particle simulations first adiabatic invariant electron drift motion time-varying electric field initial W/sup -8/ energy flux spectrum electron drift echoes 40 MeV 2.5 Earthradii 6 Earthradii 60 s }, mynotes={UNREAD}, } @ARTICLE{EgelandFeb94, author={Egeland, A. and Burke, W.J. and Maynard, N.C. and Basinska, E.M. and Winningham, J.D. and Deehr, C.S.}, title={ Ground and satellite observations of postdawn aurorae near the time of a sudden storm commencement }, journal={Journal of Geophysical Research}, volume={99}, number={A2}, year={1994}, month={Feb}, pages={2095-108}, abstract={ Meridian scanning photometer measurements taken in the magnetic postdawn sector at Longyearbyen, Svalbard, between 0300 and 0630 UT on December 29, 1981, are analyzed in conjunction with particle and field data retrieved during two near passes of the DE 2 satellite. The interval included a sudden storm commencement (SSC). Pre-SSC optical and particle measurements showed a system of arcs that are spaced at approximately 1.1 degrees intervals in magnetic latitude, embedded within the region 1 current system and span the convection reversal. The softer particle precipitation appears to have a source near the flanks of the magnetotail while the harder, more equatorward precipitation originates closer to Earth. During the SSC period the entire sky brightened, with enhanced 630.0-nm emissions extending from the northern horizon to south of magnetic zenith; intense but spatially separated 557.7-nm emissions dominated the southern horizon. DE 2 detected a more than an order of magnitude increase and near isotropization of ring current electron fluxes, enhanced precipitation from the plasma sheet and significantly decreased auroral zone convection. Region 1/region 2 currents remained, with wavelike structures superposed. On few minute travel timescales for hydromagnetic waves to pass through the system, magnetospheric particles accelerate and precipitate to increase the ionospheric conductivity. Global, field-aligned currents change more slowly. To maintain similar field-aligned currents with higher ionospheric conductances requires reduced electric fields. After 0520 UT the optical emissions settled into stable, but latitudinally separated, bands of 630.0- and 557.7-nm emissions }, keywords={ atmospheric electricity atmospheric elementary particle precipitation aurora magnetic storms magnetosphere postdawn aurorae sudden storm commencement satellite observations meridian scanning photometer measurements magnetic postdawn sector DE 2 satellite arcs region 1 current system convection reversal particle precipitation magnetotail ring current electron fluxes plasma sheet auroral zone convection region 2 currents wavelike structures hydromagnetic waves magnetospheric particles ionospheric conductivity field-aligned currents optical emissions AD 1981 12 29 557.7 nm 630.0 nm }, mynotes={UNREAD}, } @ARTICLE{RastogiSep93, title={ Longitudinal variation of sudden commencement of geomagnetic storm at equatorial stations }, journal={Journal of Geophysical Research}, volume={98}, number={A9}, year={1993}, month={Sep}, pages={15411-16}, abstract={ It is shown that the amplitude of storm sudden commencement (SSC) at a station within the equatorial electrojet belt experiences daytime enhancement, latitudinal enhancement, and longitudinal enhancement just as do the similar characteristics of the strength of the equatorial electrojet current itself. It is concluded that the sudden commencements of geomagnetic storms are associated with an increase of electric fields in the dynamo region, modifying primarily the equatorial rather than Sq currents. The V*Bz electric field generated at the magnetopause due to the impact of the solar plasma is transmitted along the magnetic lines of force to polar latitude as a dusk-to-dawn electric field which is instantaneously transmitted to the equatorial latitude as a transverse magnetic waveguide mode between a conducting ionosphere and Earth. The enhancements of SSC amplitude over the magnetic equator seem to be related to the basic ionospheric conductivity at the longitude concerned }, keywords={ electrojets ionosphere magnetic storms longitudinal variation storm sudden commencement geomagnetic storm AD 1958 to 1980 equatorial electrojet belt daytime enhancement latitudinal enhancement electric field increase dynamo region equatorial currents Sq currents solar plasma transverse magnetic waveguide conducting ionosphere Earth ionospheric conductivity }, mynotes={UNREAD}, } @ARTICLE{SibeckJan93, title={ Transient magnetic field signatures at high latitudes }, journal={Journal of Geophysical Research}, volume={98}, number={A1}, year={1993}, month={Jan}, pages={243-56}, abstract={ The author surveys GOES 2/5/6 geosynchronous and Huancayo, Peru, ground magnetometer observations at the times of 70 transient (2-10 min) events recorded at South Pole Station, Antarctica. Most South Pole events correspond to sudden sharp variations in the equatorial magnetospheric and low-latitude ground magnetic field. The exceptions occur when the South Pole events have weak amplitudes and/or Huancayo and GOES 2/5/6 are far from local noon. The corresponding features observed at GOES 5 and GOES 6 are generally similar, with a lag indicating antisunward motion. A similar antisunward motion may be inferred from the ground observations themselves. On a case-by-case and statistical basis, the characteristics of the events observed in South Pole ground magnetograms resemble those previously interpreted as sudden impulse and sudden storm commencement signatures at other high-latitude stations. These observations suggest that the transient events at South Pole form part of the magnetospheric and ionospheric response to a sudden change in the fraction of the solar wind dynamic pressure applied to the magnetosphere }, keywords={ ionosphere magnetosphere transient magnetic field signature high latitudes South Pole events antisunward motion solar wind dynamic pressure magnetosphere }, mynotes={UNREAD}, } @ARTICLE{ReevesMay92, author={Reeves, G.D. and Cayton, T.E. and Gary, S.P. and Belian, R.D.}, title={ The great solar energetic particle events of 1989 observed from geosynchronous orbit }, journal={Journal of Geophysical Research}, volume={97}, number={A5}, year={1992}, month={May}, pages={6219-26}, abstract={ Los Alamos energetic proton instruments at geosynchronous orbit observed more major solar energetic particle events during 1989 than any other year since this series of detectors began observations in 1976. The temporal flux profiles of four intervals, which contain six distinct events, are compared illustrating the uniqueness of each event. Characteristic risetime and decay time are computed for each event. During two of these events, brief order-of-magnitude increases of the proton flux are observed. They are associated with sudden commencement events and dramatic changes in the solar wind. The authors conclude that these two brief events are likely the result of shock acceleration in the solar wind }, keywords={ astronomical observations solar cosmic ray particles solar wind AD 1989 solar cosmic ray particles great solar energetic particle events proton flux profiles sudden commencement events shock acceleration solar wind }, mynotes={UNREAD}, } @ARTICLE{Yinn-Nien-HuangAug91, author={Yinn-Nien Huang and Kang Cheng}, title={ Ionospheric disturbances at the equatorial anomaly crest region during the March 1989 magnetic storms }, journal={Journal of Geophysical Research}, volume={96}, number={A8}, year={1991}, month={Aug}, pages={13953-65}, abstract={ On March 6, 1989, the largest sunspot group since 1982 came into view as it moved out of the eastern limb of the Sun. The intensive ionospheric observations at Lunping Observatory and Chungli Ionosphere Station during this period recorded 30 solar flares manifested as shortwave fade-outs, sudden frequency deviations, and solar flare effects and three storm sudden commencement (SSC)-type geomagnetic storms, among which the March 13 SSC-type geomagnetic storm triggered an unusually severe ionospheric disturbance. The ionospheric total electron content, the critical frequency of the F/sub 2/ layer, f/sub 0/F/sub 2/, and the virtual heights at given frequencies all show wavelike up-and-down oscillations of the ionosphere }, keywords={ ionosphere magnetic storms SSC AD 1989 03 ionosphere disturbance F-region China equatorial anomaly crest region Lunping Chungli shortwave fade-outs sudden frequency deviations solar flare effects storm sudden commencement ionospheric disturbance electron content critical frequency F/sub 2/ layer wavelike up-and-down oscillations }, mynotes={UNREAD}, } @ARTICLE{LeppingJun91, author={Lepping, R.P. and Burlaga, L.F. and Tsurutani, B.T. and Ogilvie, K.W. and Lazarus, A.J. and Evans, D.S. and Klein, L.W.}, title={ The interaction of a very large interplanetary magnetic cloud with the magnetosphere and with cosmic rays }, journal={Journal of Geophysical Research}, volume={96}, number={A6}, year={1991}, month={Jun}, pages={9425-38}, abstract={ A large interplanetary magnetic cloud was observed in the mid-December 1982 data from ISEE 3. The magnetic field measured throughout the main portion of the cloud was fairly tightly confined to a plane as it changed direction by 174 degrees . Throughout the cloud's passage, IMP 8 provided observations of its interaction with the bow shock and magnetopause. Near the end of the cloud passage, at 0806 UT on December 17, ISEE 3 observed an oblique fast forward interplanetary shock closely coincident in time with a geomagnetic storm sudden commencement. The shock was in the process of overtaking the cloud. The index Dst decreased monotonically by approximately=130 nT during the 2-day cloud passage by the Earth and was well correlated with the B/sub z/-component of the interplanetary magnetic field. There was no significant decrease in the cosmic ray intensity at this time of rather strong, smoothly changing fields. However, a Forbush decrease did occur immediately after the interplanetary shock, during a period of significant field turbulence }, keywords={ astronomical observations cosmic ray propagation cosmic ray solar modulation interplanetary magnetic fields interplanetary matter magnetic storms magnetosphere shock waves solar wind heliocentric radial size AD 1982 12 14 to 19 magnetic cloud-bow shock interaction AD 1982 12 17 magnetic cloud-magnetopause interaction shock speed magnetic field direction change solar wind speed magnetic field turbulence helical magnetic field very large interplanetary magnetic cloud magnetosphere mid-December 1982 data ISEE 3 oblique fast forward interplanetary shock geomagnetic storm sudden commencement index B/sub z/-component interplanetary magnetic field cosmic ray intensity smoothly changing fields Forbush decrease 60 Gm 2 d 1 AU 390 km/s 700 km/s }, mynotes={UNREAD}, } @ARTICLE{BravoApr91, author={Bravo, S. and Mendoza, B. and Perez-Enriquez, R.}, title={ Coronal holes as sources of large-scale solar wind disturbances and geomagnetic perturbations }, journal={Journal of Geophysical Research}, volume={96}, number={A4}, year={1991}, month={Apr}, pages={5387-96}, abstract={ Presents theoretical and observational evidence that low-latitude unstable coronal holes may be, in some circumstances, the source of widespread interplanetary shocks and of the consequent geomagnetic perturbations. The shock events tracked by interplanetary scintillation in the study of Hewish and Bravo (1986) are reanalysed. These events produced the sudden commencement of a geomagnetic storm, in terms of an alternative flare, disappearing filament, or coronal hole eruption origin. The main conclusion of this study is that there are good reasons to consider coronal holes as sources of shock type interplanetary disturbances and that more effort should be made to monitor coronal holes continuously }, keywords={ magnetic storms magnetosphere solar corona solar wind solar corona source coronal hole magnetic storm solar wind magnetosphere interaction Sun large-scale solar wind disturbances geomagnetic perturbations low-latitude interplanetary shocks sudden commencement coronal hole eruption origin }, mynotes={UNREAD}, } @ARTICLE{CahillJun90, author={Cahill, L.J. and Jr., Lin and N.G., Waite and J.H., Engebretson and M.J. and Sugiura, M.}, title={ Toroidal standing waves excited by a storm sudden commencement: DE 1 observations }, journal={Journal of Geophysical Research}, volume={95}, number={A6}, year={1990}, month={Jun}, pages={7857-67, 8299}, abstract={ A 74-nT sudden commencement on July 13, 1982, was observed in the magnetosphere with instruments on the Dynamics Explorer 1 satellite. Inbound, near L=4.5, the satellite was located at 1524 magnetic local time and 20 degrees magnetic latitude. The sudden commencement established a strong, east-west oscillation, with 100-s period, which was observed in the magnetic field, the electric field, and the plasma flow velocity records. There was also a compressional component of this 100-s oscillation and a rapidly damped 300-s compressional pulsation. The compressional oscillations may be evidence of cavity resonances, excited by the sudden commencement. The cavity waves may, in turn, couple to toroidal waves in field line resonance at the satellite location }, keywords={ ionosphere magnetic storms magnetosphere micropulsations ULF wave SSC toroidal standing wave micropulsation ionosphere AD 1982 07 13 magnetic storm magnetic pulsation storm sudden commencement magnetosphere east-west oscillation cavity resonances }, mynotes={UNREAD}, } @ARTICLE{FairfieldNov89, author={Fairfield, D.H. and Baker, D.N. and Craven, J.D. and Elphic, R.C. and Fennell, J.F. and Frank, L.A. and Richardson, I.G. and Singer, H.J. and Slavin, J.A. and Tsurutani, B.T. and Zwickl, R.D.}, title={ Substorms, plasmoids, flux ropes, and magnetotail flux loss on March 25, 1983: CDAW 8 }, journal={Journal of Geophysical Research}, volume={94}, number={A11}, year={1989}, month={Nov}, pages={15135-52}, abstract={ During a 9-hour period following a storm sudden commencement on March 25, 1983, six spacecraft near geosynchronous orbit, one over the pole, and three in the magnetotail monitored a complex sequence of magnetospheric variations. Magnetic field compressions associated with the sudden commencement were seen first by the near-Earth spacecraft and subsequently by the three downtail spacecraft. Ground magnetograms and synchronous orbit data are used to identify seven substorm intensifications during this geomagnetically active period. All the observations are consistent with the substorm-associated release of a plasmoid at a neutral line near 20 R/sub E/; however, the classical north-south variation of the plasma sheet magnetic field thought to be characteristic of the passage of a plasmoid in the deep tail was not seen in every case }, keywords={ magnetic storms magnetosphere plasma Coordinated Data Analysis Workshop 8 AD 1983 03 25 magnetic storm plasmoids flux ropes magnetotail flux loss CDAW 8 storm sudden commencement magnetospheric variations field compressions substorm intensifications plasma sheet }, mynotes={UNREAD}, } @ARTICLE{LaaksoJun89, author={Laakso, H. and Schmidt, R.}, title={ Pc 4-5 pulsations in the electric field at geostationary orbit (GEOS 2) triggered by sudden storm commencements }, journal={Journal of Geophysical Research}, volume={94}, number={A6}, year={1989}, month={Jun}, pages={6626-32}, abstract={ A frequently observed feature in the electric field data on board GEOS 2 is the sudden occurrence of large-amplitude Pc 4-5 waves lasting from a few tens of minutes up to a few hours. For the events chosen it was found that the large-amplitude events (>or=2 mV/m) are often accompanied by magnetic field data containing the signature of a compression of the magnetosphere. The occurrence of the compression coincides with the recording of an ssc (sudden storm commencement) on ground. The dc electric field measurements suggest that the E*B/B/sup 2/ drift rapidly and temporarily rotates into a tailward plasma drift at 6.6 R/sub E/. The transient disturbances of the magnetopause also changed the widely scattered frequency distribution of the nearly always present fluctuations in the Pc 4-5 range into a narrow-band distribution, with frequency large amplitudes, after the occurrence of the ssc }, keywords={ micropulsations SSC Pc 4 Pc 5 magnetosphere magnetic pulsation sudden commencement AD 1979 03 electric field geostationary orbit sudden storm commencements sudden occurrence large-amplitude }, mynotes={UNREAD}, } @ARTICLE{HamiltonDec88, author={Hamilton, D.C. and Gloeckler, G. and Ipavich, F.M. and Studemann, W. and Wilken, B. and Kremser, G.}, title={ Ring current development during the great geomagnetic storm of February 1986 }, journal={Journal of Geophysical Research}, volume={93}, number={A12}, year={1988}, month={Dec}, pages={14343-55}, abstract={ The largest geomagnetic storm in recent decades began with a sudden commencement on February 6, 1986, developed slowly over the next two days, and, with a rapid intensification late on February 8, reached a minimum Dst of -312 nT during the first hour of February 9. Initial recovery was rapid, but full recovery took more than a month. In this paper the authors follow the ring current development during the storm using particle measurements from the charge-energy-mass (CHEM) instrument on the Active Magnetospheric Particle Tracer Explorers (AMPTE) CCE spacecraft. The energy content of the ring current ions is compared with that expected from observed Dst values utilizing for the first time composition coverage over nearly the complete ring current energy range (1-310 keV/e). The ring current composition is followed for five days from prestorm quiet time to early recovery phase. Ions of both solar wind and ionospheric origin are important constituents of the storm time ring current }, keywords={ electrojets magnetic storms ring current development magnetosphere great magnetic storm AD 1986 02 09 electrojet AD 1986 02 great geomagnetic storm storm time ring current }, mynotes={UNREAD}, } @ARTICLE{CaneJan88, title={ The large-scale structure of flare-associated interplanetary shocks }, journal={Journal of Geophysical Research}, volume={93}, number={A1}, year={1988}, month={Jan}, pages={1-6}, abstract={ The large-scale structure of flare-associated interplanetary shocks is investigated by examining the properties of 116 shocks which originated in solar flare events during a 18.7-year period commencing mid-May 1967. The best average representation of these shocks is an expansion which is uniform over about 100 degrees . The highest compression ratio across the shock ( approximately 2.7) is about 15 degrees west of the radial from the flare site. The loose coupling of shocks and their drivers is supported by the observation that drivers are generally only detected for shocks originating near central meridian. A comparison of the numbers of shocks per year with the numbers of sudden commencement geomagnetic storms indicates that the percentage of shocks at 1 AU which originate in flare events is less than 50% }, keywords={ solar wind solar wind plasma shock wave AD 1967 to 1986 large-scale structure flare-associated interplanetary shocks solar flare events compression ratio }, mynotes={UNREAD}, } @ARTICLE{McDiarmidMay87, author={McDiarmid, D.R. and Nielsen, E.}, title={ Simultaneous observation of monochromatic and variable period geomagnetic pulsations }, journal={Journal of Geophysical Research}, volume={92}, number={A5}, year={1987}, month={May}, pages={4449-57}, abstract={ On February 4, 1983, following a storm sudden commencement, a monochromatic and a variable period pulsation were simultaneously observed by the Scandinavian Twin Auroral Radar Experiment (STARE) and Sweden and Britain Radar Experiment (SABRE) radar systems. Both pulsations differed from previously analyzed examples of their class. The phase of the monochromatic pulsation increased linearly with latitude rather than decreased. Its amplitude remained relatively constant over the latitude interval of linear phase change. The variable period pulsation experienced a change of orientation of its essentially linear polarization diagram is association with a discontinuity of its period. The variable period pulsation was thus manifest in both the toroidal and poloidal components }, keywords={ microcomputers magnetosphere simultaneous micropulsation AD 1983 02 04 monochromatic variable period geomagnetic pulsations variable period pulsation phase }, mynotes={UNREAD}, } @ARTICLE{ImhofFeb87, author={Imhof, W.L. and Voss, H.D. and Mobilia, J. and Datlowe, D.W.}, title={ Bremsstrahlung X-ray mappings of an intense, widespread, and pulsating electron precipitation event following a sudden commencement }, journal={Journal of Geophysical Research}, volume={92}, number={A2}, year={1987}, month={Feb}, pages={1211-17}, abstract={ For the first time, remote bremsstrahlung X-ray spatial, temporal, and spectral mappings from a satellite are presented for a strong energetic electron precipitation event following a sudden commencement. After the sudden commencement of July 13, 1982, and at the beginning of a magnetospheric substorm, X-rays were observed over a period of more than 4 min from the P78-1 spacecraft at 600-km altitude. The X-rays above 21 keV were emitted over a magnetic local time (MLT) interval spanning 6 hours. Five precipitating temporal spikes were observed with coherency over wide longitude intervals of 3 hours or more in MLT near midnight. The energy spectra over broad longitude intervals tended to be harder simultaneously at the times of greatest X-ray intensity }, keywords={ atmospheric electron precipitation atmospheric radiation upper atmosphere ionosphere AD 1982 07 13 upper atmosphere X-ray mappings intense widespread pulsating electron precipitation event sudden commencement bremsstrahlung strong energetic electron precipitation substorm }, mynotes={UNREAD}, } @ARTICLE{McDiarmidJan87, author={McDiarmid, D.R. and Nielsen, E.}, title={ Coherent radar observations of a storm sudden commencement having a preliminary reverse impulse }, journal={Journal of Geophysical Research}, volume={92}, number={A1}, year={1987}, month={Jan}, pages={159-67}, abstract={ Observations of the February 4, 1983, storm sudden commencement (ssc) by the STARE and SABRE radar systems are presented. The observing stations were in the dusk sector, where the ssc was accompanied by a preliminary reverse impulse (PRI). The radar data show the PRI to be a consequence of the ssc compression wave producing an initial antisunward flow. The polarization of the ssc electric field in the ionosphere is seen to have both longitudinal and latitudinal structure. The observations are discussed in terms of the propagation of the ssc disturbance throughout the magnetosphere }, keywords={ atmospheric electricity ionosphere magnetic storms magnetosphere AD 1983 02 03 to 04 magnetic storm storm sudden commencement preliminary reverse impulse STARE SABRE dusk sector compression wave initial antisunward flow polarization electric field ionosphere longitudinal latitudinal structure propagation disturbance magnetosphere }, mynotes={UNREAD}, } @ARTICLE{TholenDec86, author={Tholen, S.M. and Armstrong, T.P. and Lanzerotti, L.J.}, title={ Correlation of geomagnetic storm sudden commencement with triggered magnetospheric particle bursts }, journal={Journal of Geophysical Research}, volume={91}, number={A12}, year={1986}, month={Dec}, pages={13717-22}, abstract={ A previous investigation (Tholen and Armstrong, 1986) demonstrated that the occurrence of a storm sudden commencement (SSC) significantly increases the probability of observing energetic particle bursts in the magnetosphere, particularly in the magnetotail. An evaluation of all such observed particle bursts following SSCs between 1973 and 1983 is reported in this article. Data from five magnetometer stations near L=4 were used to investigate the details of the correlations between SSC amplitudes, occurrence times, particle burst characteristics, and triggering probability. The results indicate that SSC amplitude apparently controls the probability of a subsequent particle burst if the observation location is in the magnetosheath or magnetotail; the observed intensity of the burst, however, appears to be unrelated to the size of the SSC }, keywords={ magnetic storms magnetosphere triggered particle burst SSC magnetic storm triggered particle burst correlation geomagnetic storm sudden commencement magnetospheric magnetosphere amplitudes occurrence times triggering probability magnetosheath magnetotail }, mynotes={UNREAD}, } @ARTICLE{GuptaOct86, author={Gupta, R. and Desai, J.N. and Raghavarao, R. and Sekar, R. and Sridharan, R. and Narayanan, R.}, title={ Excess heating over the equatorial latitudes during storm sudden commencement }, journal={Geophysical Research Letters}, volume={13}, number={10}, year={1986}, month={Oct}, pages={1055-8}, abstract={ Temperatures of the equatorial thermosphere were obtained from the rocket released vapour clouds during (i) geomagnetically quiet, and (ii) just after (<2 hrs) a sudden commencement. These measurements of thermospheric temperatures at different altitudes during sudden commencement are the first of their kind. The results reveal larger temperatures (>400-500K) than that expected by the Jacchia 77 model during disturbed periods, while the quite day measurements agree well with the model predictions. The possible sources of energy that account for the excess temperatures are discussed in the context of the present measurements }, keywords={ atmospheric temperature magnetic storms thermosphere magnetic storms energy sources atmosphere AD 1982 02 16 AD 1982 03 01 heating equatorial latitudes storm sudden commencement thermosphere rocket released vapour clouds temperatures Jacchia 77 model disturbed periods }, mynotes={UNREAD}, } @ARTICLE{KikuchiMar86, title={ Evidence of transmission of polar electric fields to the low latitude at times of geomagnetic sudden commencements }, journal={Journal of Geophysical Research}, volume={91}, number={A3}, year={1986}, month={Mar}, pages={3101-5}, abstract={ The HF Doppler frequency deviation associated with the geomagnetic sudden commencement (sc), called SCF, consists of the negative preliminary frequency deviation (PFD) and the succeeding positive main frequency deviation (MFD) when observed during the night at geomagnetic low latitude (geomagnetic latitude=25 degrees ). This type of HF Doppler frequency deviation, SCF(-or+), corresponds to the sc(+) at low latitude and the sc(-or+) (=sc*) at high latitude. The SCF(-or+) starts earlier than the low latitude sc by 50 s, while it occurs simultaneously with the high latitude sc* within a time accuracy of 10 s. This result implies that the negative PFD of the nighttime SCF(-or+) is caused by a dusk-to-dawn polar electric field responsible for the preliminary reverse impulse (PRI) of sc*, the occurrence of which is earlier than the occurrence of the world-wide geomagnetic increase. Consequently, the magnetospheric electric field generated at the onset of sc is transmitted to the low-latitude ionosphere by way of the polar ionosphere, earlier than the direct transmission through the magnetosphere by compressional hydromagnetic waves }, keywords={ magnetic storms magnetosphere magnetic storm magnetosphere PFD SC MFD PRI transmission polar electric fields low latitude geomagnetic sudden commencements HF Doppler frequency deviation sudden commencement SCF negative preliminary frequency deviation main frequency deviation dusk-to-dawn polar electric field preliminary reverse impulse onset polar ionosphere }, mynotes={UNREAD}, } @ARTICLE{WilkenFeb86, author={Wilken, B. and Baker, D.N. and Higbie, P.R. and Fritz, T.A. and Olson, W.P. and Pfitzer, K.A.}, title={ Magnetospheric configuration and energetic particle effects associated with a SSC: a case study of the CDAW 6 event on March 22, 1979 }, journal={Journal of Geophysical Research}, volume={91}, number={A2}, year={1986}, month={Feb}, pages={1459-73}, abstract={ Three geostationary satellites, GEOS 2, 1976-059, 1977-007, located near noon, near midnight, and 0400 LT, respectively, observed the global energetic particle signatures produced by the storm sudden commencement (SSC) at 0826 UT on March 22, 1979. The SSC-induced magnetopause compression generated a steplike wave which traversed the magnetosphere within 2 min. The associated induced electric fields substantially altered both particle energies and drift motions. Local observations of spectral distributions at all longitudes are compared with predictions from a simple model, thus allowing some inference on the radial properties of the particles' energy distribution function. The nonadiabatic compression during the SSC modified existing drift orbits of energetic particles and increased drift shell magnetopause displacements are studied }, keywords={ magnetic storms magnetosphere AD 1979 03 22 magnetopause magnetosphere configuration magnetic storm energetic particle effects SSC CDAW 6 event storm sudden commencement SSC-induced magnetopause compression steplike wave magnetosphere }, mynotes={UNREAD}, } @ARTICLE{KikuchiDec85, author={Kikuchi, T. and Araki, T.}, title={ Preliminary positive impulse of geomagnetic sudden commencement observed at dayside middle and low latitudes }, journal={Journal of Geophysical Research}, volume={90}, number={A12}, year={1985}, month={Dec}, pages={12195-200}, abstract={ It is found that an impulsive geomagnetic increase, named the preliminary positive impulse (PPI), often precedes the main impulse (MI) of geomagnetic sudden commencement at the dayside middle latitude (Memambetsu). The duration time of the PPI is about 1 min, and the average magnitude is 16 nT. The PPI also appears near the geomagnetic equator (Guam), although the occurrence is less frequent. No equatorial enhancements are present in the PPI, while the MI is enhanced appreciably at Guam. Most of PPI's accompany an electric field with a westward component in the ionospheric F region, as observed with the HF Doppler technique. These observational results lead to a conclusion that the PPI is transmitted from above the ionosphere by a compressional hydromagnetic wave }, keywords={ magnetic storms PPI preliminary impulse magnetic storm magnetosphere Preliminary positive impulse geomagnetic sudden commencement dayside low latitudes main impulse middle latitude compressional hydromagnetic wave }, mynotes={UNREAD}, } @ARTICLE{ShelleyMay85, author={Shelley, E.G. and Klumpar, D.M. and Peterson, W.K. and Ghielmetti, A. and Balsiger, H. and Geiss, J. and Rosenbauer, H.}, title={ AMPTE/CCE observations of the plasma composition below 17 keV during the September 4, 1984 magnetic storm }, journal={Geophysical Research Letters}, volume={12}, number={5}, year={1985}, month={May}, pages={321-4}, abstract={ Observations from the Hot Plasma Composition Experiment on the AMPTE/CCE spacecraft during the magnetic storm of 4-5 September 1984 reveal that significant injection of ions of terrestrial origin accompanied the storm development. The compression of the magnetosphere at storm sudden commencement carried the magnetopause inside the CCE orbit clearly revealing the shocked solar wind plasma. A build up of suprathermal ions is observed near the plasmapause during the storm main phase and recovery phase. Pitch angle distributions in the ring current during the main phase show differences between H/sup +/ and O/sup +/ that suggest mass dependent injection, transport and/or loss processes }, keywords={ magnetic storms magnetosphere trapped particle AD 1984 09 04 plasma composition magnetic storm ions terrestrial origin storm development compression sudden commencement magnetopause suprathermal ions ring current }, mynotes={UNREAD}, } @ARTICLE{PotemraMay85, author={Potemra, T.A. and Zanetti, L.J. and Acuna, M.H.}, title={ AMPTE/CCE magnetic field studies of the September 4, 1984 storm }, journal={Geophysical Research Letters}, volume={12}, number={5}, year={1985}, month={May}, pages={313-16}, abstract={ A large geomagnetic storm began on September 4, 1984 with a storm sudden commencement (SSC) reported at 07:46 UT. Observations acquired with the AMPTE/CCE Magnetic Field Experiment have been used to determine the overall magnetic field environment during the evolution of the storm. The spacecraft observed a magnetic field change indicating a sudden impulse at 06:33 UT. Magnetic field fluctuations and six magnetopause crossings were observed. The observations indicate that the entire magnetosphere was 'breathing' in and out with a period of about 45 minutes. Further details of this magnetic storm were recorded }, keywords={ magnetic storms AD 1984 09 04 magnetic storm magnetosphere large geomagnetic storm }, mynotes={UNREAD}, } @ARTICLE{KnottFeb85, author={Knott, K. and Pedersen, A. and Wedeken, U.}, title={ GEOS 2 electric field observations during a sudden commencement and subsequent substorms }, journal={Journal of Geophysical Research}, volume={90}, number={A2}, year={1985}, month={Feb}, pages={1283-8}, abstract={ Presents and discusses electric field and plasma density data obtained by the GEOS 2 double probe experiment on March 22, 1979. The observation period encompasses a sudden storm commencement and two consecutive substorms. Ground and satellite based magnetic observations were also made. The influence of the solar wind on magnetospheric dynamics was also studied. Solar wind discontinuities cause strong electric field transients in the dayside magnetosphere. These transients are followed by Pc 4 oscillations of considerable amplitude. The data also show the existence of DC electric fields during buildup, onset and expansion phase of the two substorms }, keywords={ magnetic storms micropulsations magnetosphere magnetic storm CDAW 6 AD 1979 03 22 micropulsation electric field sudden commencement subsequent substorms plasma density sudden storm commencement consecutive substorms transients Pc 4 buildup onset expansion phase }, mynotes={UNREAD}, } @ARTICLE{WolfAug82, author={Wolf, R.A. and Harel, M. and Spiro, R.W. and Voigt, G.-H. and Reiff, P.H. and Chen, C.-K.}, title={ Computer simulation of inner magnetospheric dynamics for the magnetic storm of July 29, 1977 }, journal={Journal of Geophysical Research}, volume={87}, number={A8}, year={1982}, month={Aug}, pages={5949-62}, abstract={ Presents preliminary results of applying the Rice convection model to the early main phase of the magnetic storm of July 29, 1977. The computer model self-consistently computes electric fields and currents, as well as plasma distributions and velocities, in the inner-magnetosphere/ionosphere system. In the equatorial plane, the region modeled includes geocentric distances less than about the magneto-pause standoff distance. On the basis of solar wind parameters and the AL index as input, the model predicts the injection of plasma-sheet plasma to form a substantial storm time ring current. Birkeland currents are also calculated. The authors examine the possibility that the magnetic field might be so highly inflated that 60 degrees field lines might extend to the outer magnetosphere. In the model, distortion of the inner edge of the plasma sheet by magnetospheric compression associated with sudden commencement temporarily disturbs the normal Birkeland-current pattern. The normal tendency for the plasma sheet's inner edge to shield low L values from the convection electric field is also temporarily disrupted }, keywords={ ionosphere magnetic storms magnetosphere inner magnetosphere AD 1977 07 29 electric current ionosphere plasma motion Birkeland configuration dynamics magnetic storm Rice convection model early main phase electric fields injection plasma-sheet ring current }, mynotes={UNREAD}, } @ARTICLE{BakerAug82, author={Baker, D.N. and Fritz, T.A. and Wilken, B. and Higbie, P.R. and Kaye, S.M. and Kivelson, M.G. and Moore, T.E. and Studemann, W. and Masley, A.J. and Smith, P.H. and Vampola, A.L.}, title={ Observation and modeling of energetic particles at synchronous orbit on July 29, 1977 }, journal={Journal of Geophysical Research}, volume={87}, number={A8}, year={1982}, month={Aug}, pages={5917-32}, abstract={ In the 12 hours following a worldwide storm sudden commencement at 0027 UT on July 29 there was a series of at least four substorms, the last and largest of which exhibited an expansion phase onset at approximately 1200 UT. Data from six spacecraft in three general local time groupings were examined, and vector magnetic field data and energetic electron and ion data from approximately 15 keV to >2 meV were employed. Four primary types of studies were carried out: (1) timing and morphology of energetic particle injections; (2) variation of particle phase space densities; (3) measurement of boundary motions; and (4) adiabatic modeling, which included injection, large-scale convection, corotation, and gradient drifts. For the 1200 UT substorm it is concluded that there was a substantial flux dropout in a broad sector near local midnight because of a large-scale boundary motion, followed by a recovery to a predropout configuration. There were then several subsequent injection events with distinct onsets, for which ion anisotropy information suggests an inward motion of particles from outside of geostationary orbit. A number of other deductions were made using the observed data }, keywords={ magnetic storms magnetosphere AD 1977 07 29 magnetosphere substorm trapped particle SSC magnetic storm energetic particles sudden commencement expansion phase onset injection }, mynotes={UNREAD}, } @ARTICLE{OlsonAug82, title={ Pc 1 emissions in the afternoon sector prior to the July 29, 1977 sudden commencement }, journal={Journal of Geophysical Research}, volume={87}, number={A8}, year={1982}, month={Aug}, pages={5895-900}, abstract={ A series of three structured Pc 1 events were observed prior to the July 29, 1977, sudden commencement by magnetometer stations at College, Alaska; MacQuarie Island, Australia; and Vostok, Antarctica. Signal characteristics of the events lead to the inference that the near conjugate College and MacQuarie Island stations were near the source field lines for the second of these events. From the growth rates for ion cyclotron waves calculated from linearized equations for an anisotropic, drifting plasma the authors have inferred the presence of freshly injected plasma in the afternoon magnetosphere after 2330 UT at L=5.4. This is consistent with the increased convection to be expected with the observed southward turning of the interplanetary magnetic field prior to the sudden commencement }, keywords={ micropulsations Pc 1 radiowave emission injection AD 1977 07 29 magnetic storm micropulsation flow afternoon sector sudden commencement ion cyclotron waves plasma magnetosphere convection }, mynotes={UNREAD}, } @ARTICLE{KnottAug82, author={Knott, K. and Fairfield, D. and Korth, A. and Young, D.T.}, title={ Observations near the magnetopause at the onset of the July 29, 1977, sudden storm commencement }, journal={Journal of Geophysical Research}, volume={87}, number={A8}, year={1982}, month={Aug}, pages={5888-94}, abstract={ Observations by GEOS 1, supported by data collected by IMP 7, IMP 8 and ATS 6 during the July 29, 1977, sudden storm commencement (SSC) have been used to derive the magnetopause's position, velocity and thickness. Particle, field and wave data from GEOS 1 have been used to establish the satellite's position with respect to the magnetopause. After the initial crossing of the magnetopause, the satellite remained in the magnetosheath for most of the interval considered, occasionally encountering what are interpreted as 'open magnetic field lines'. When the spacecraft was in the magnetosheath, duskward plasma flows tangential to the magnetopause are derived from electric field measurements. The flow velocity was correlated with IMF direction (north or south). On occasions atypical magnetosheath conditions were observed }, keywords={ magnetic storms magnetosphere magnetosphere magnetic storm sudden commencement AD 1977 07 29 SSC solar wind interaction plasma flow magnetopause onset sudden storm commencement position thickness magnetosheath }, mynotes={UNREAD}, } @ARTICLE{MankaAug82, author={Manka, R.H. and Fritz, T.A. and Johnson, R.G. and Wolf, R.A. and Teague, M.J. and Vette, J.I.}, title={ Overview of the IMS July 29, 1977, magnetic storm analysis }, journal={Journal of Geophysical Research}, volume={87}, number={A8}, year={1982}, month={Aug}, pages={5871-80}, abstract={ Reviews the physical characteristics and temporal development of a significant IMS magnetospheric event: the sudden commencement and multiple substorms of July 29, 1977. An interplanetary shock, superimposed on relatively high solar wind densities, forced the magnetopause at 0027 UT in past the position of GEOS 1 ( approximately 6.7 R/sub E/). Following this compression, as well as periods of southward IMF, a series of substorms culminated in a very large substorm with peak electrojet current at 1230 UT, followed by a relatively quiet recovery phase. A large collection of international data from eleven spacecraft, seven ground stations and a variety of theoretical calculations are analysed. Emphasis was placed on energy transfer and magnetospheric dynamics }, keywords={ magnetic storms AD 1977 07 29 magnetosphere magnetopause solar wind interaction magnetic storm development sudden commencement multiple substorms }, mynotes={UNREAD}, } @ARTICLE{ArakiApr82, author={Araki, T. and Iyemori, T. and Tsunomura, S. and Kamei, T. and Maeda, H.}, title={ Detection of an ionospheric current for the preliminary impulse of the geomagnetic sudden commencement }, journal={Geophysical Research Letters}, volume={9}, number={4}, year={1982}, month={Apr}, pages={341-44}, abstract={ MAGSAT observed a geomagnetic sudden commencement at an altitude of 550 km on its dawnside orbit above the South Atlantic Ocean. The H-component of the magnetic field increased monotonically by 46 nT in about 4 minutes, while the D-component decreased westward by 10 nT in the first 1-2 minutes and then increased gradually. There was no significant deviation in the Z-component. The comparison with ground-based magnetograms showed that the negative impulse of the D-component provided the first experimental evidence of the global ionospheric current system for the preliminary impulse of the geomagnetic sudden commencement }, keywords={ atmospheric electricity ionosphere magnetic storms SC ionosphere electric current magnetosphere geomagnetic variation disturbance magnetic storm preliminary impulse sudden commencement geomagnetic }, mynotes={UNREAD}, } @ARTICLE{SatoJan80, title={ Morphological features of the winter anomaly in ionospheric absorption of radio waves at middle latitudes }, journal={Journal of Geophysical Research}, volume={85}, number={A1}, year={1980}, month={Jan}, pages={197-205}, abstract={ The spatial extent and duration of the winter anomaly, i.e., anomalous and large enhancement in ionospheric absorption of HF and MF waves occurring on groups of winter days at middle latitudes, are examined on the basis of f/sub min/ data at 18 stations in USSR, Japan, and North America during the periods November-February in 1971-1972 and 1972-1973, considering that f/sub min/ enhancement represents an increased ionospheric absorption of HF and MF waves. The relationship between the phenomena of winter anomaly and geomagnetic storm is also examined. It is found that the winter anomaly occurs simultaneously in an extensive daytime area at middle latitudes, at least in some scattered region over the area, whose longitudinal extent reaches at most approximately 100 degrees . The southern boundary of the anomaly seems to be controlled geomagnetically and located below 30 degrees in geomagnetic latitude. Also it is shown that the winter anomaly seems to be associated with geomagnetic storms, mainly sc (sudden commencement) storms, because outstanding enhancements in wave absorption begin usually 1-3 days after the beginning of an individual sc storm and last for more than a few days with decreasing magnitude. It is suggested that the winter anomaly is ascribed to ionization enhancements in the lower D-region due to precipitating electrons from the outer atmosphere, mainly from the slot region associated with geomagnetic storms }, keywords={ atmospheric electron precipitation atmospheric ionisation D-region electromagnetic wave absorption ionospheric electromagnetic wave propagation magnetic storms radiowave propagation middle latitudes spatial extent MF waves f/sub min/ data USSR Japan North America extensive daytime area geomagnetic latitude geomagnetic storms ionization enhancements lower D-region slot region ionosphere winter absorption anomaly morphology radio waves absorption enhancement HF waves AD 1971 11 to 1973 02 winter anomaly southern boundary sudden commencement magnetic storms electron precipitation anomaly duration }, mynotes={UNREAD}, } @ARTICLE{BrownMay78, title={ On sudden commencement absorption events at the south pole and their relation to the latitude of the lower cleft boundary }, journal={Journal of Geophysical Research}, volume={83}, number={A5}, year={1978}, month={May}, pages={2205-7}, abstract={ From 7 years (1966-1973) of riometer data from the south pole (74.2 degrees invariant latitude), 43 sudden commencements of magnetic storms were examined for sudden commencement absorption (sca) events and the possible influence of the lower cleft boundary latitude on electron precipitation at that site. For 17 of the events, interplanetary magnetic field (IMF) data are available to predict the position of the lower cleft boundary. Three of the sca events at the south pole occurred during IMF conditions when the predicted cleft boundary, including the effect of magnetic activity (AE), was equatorward of that site by 2 degrees -4 degrees . The observation of sudden commencement electron precipitation at the south pole at these times indicates that the cleft region involves closed field lines }, keywords={ atmospheric electron precipitation electromagnetic wave absorption ionospheric electromagnetic wave propagation magnetic storms magnetosphere sudden commencement absorption events south pole latitude riometer data magnetic storms lower cleft boundary latitude electron precipitation interplanetary magnetic field magnetic activity electron precipitation closed field lines region 1966 to 1973 74.2 degrees invariant latitude magnetosphere cleft }, mynotes={UNREAD}, } @ARTICLE{RobleMar78, author={Roble, R.G. and Richmond, A.D. and Oliver, W.L. and Harper, R.M.}, title={ Ionospheric effects of the gravity wave launched by the September 18, 1974, sudden commencement }, journal={Journal of Geophysical Research}, volume={83}, number={A3}, year={1978}, month={Mar}, pages={999-1009}, abstract={ A sudden commencement of a geomagnetic storm occurred at 1434 UT on September 18, 1974. A traveling ionospheric disturbance was detected about an hour later by the incoherent scatter radar at Millstone Hill, Massachusetts (42.6 degrees N, 71.5 degrees W), and still later by the incoherent scatter radar at Arecibo, Puerto Rico (18.3 degrees N, 66.7 degrees W). Measurements of the vertical distribution of electron temperature, ion temperature, and electron density made during the passage of the disturbance at both stations show significant perturbations in comparison to the geomagnetic quiet time values obtained on the previous day. Characteristics of the thermospheric gravity wave are calculated from a time-dependent dynamic model of the thermosphere }, keywords={ gravity waves ionosphere magnetic storms thermosphere September 18, 1974 sudden commencement geomagnetic storm incoherent scatter radar Millstone Hill, Massachusetts Arecibo, Puerto Rico electron temperature ion temperature electron density thermospheric gravity wave dynamic model ionospheric effects travelling ionospheric disturbance }, mynotes={UNREAD}, } @ARTICLE{BrownJun77, title={ Sudden commencement absorption events at the edge of the polar cap }, journal={Journal of Geophysical Research}, volume={82}, number={16}, year={1977}, month={Jun}, pages={2433-5}, abstract={ Examination of riometer records from a 5-year period (1967-1971) at Godhavn, Greenland (77.2 degrees invariant latitude), shows the presence of sudden commencement absorption on two occasions, both during the late spring and early summer months in the northern hemisphere. One event occurred during quiet geomagnetic conditions when the interplanetary field was northward; the other event occurred during disturbed conditions when the predicted position of the equatorward boundary of the polar cusp was 2 degrees equatorward of the observing site }, keywords={ ionospheric electromagnetic wave propagation magnetic storms radiowave propagation polar cap riometer records Godhavn Greenland sudden commencement absorption ionosphere }, mynotes={UNREAD}, } @ARTICLE{SawyerOct76, title={ Proton flux increases, flares, and sudden commencements }, journal={Journal of Geophysical Research}, volume={81}, number={28}, year={1976}, month={Oct}, pages={5157-62}, abstract={ A systematic study of increases of flux of 10-, 30-, and 60-MeV protons shows that some are associated with flares, but many are more closely related to sudden commencement (sc) of a geomagnetic disturbance or to crossing of a sector boundary (sb). Some of these sc- and sb-related enhancements occur as second maxima of a flare-associated increase, and these have energy spectra closely similar to the spectrum of the primary increase, a finding indicating that these protons, too, are accelerated in the flare. Isolated sc- and sb-related increases can be regarded as extreme examples of second maxima, in which the primary maximum is below the threshold of detection, and only the maximum of the increase, which occurs 2 or 3 days after the initiating flare, is seen. The occurrence rate of these slow increases mimics that of major flares and of flare-related increases, and so it is concluded that these protons are also flare accelerated }, keywords={ cosmic ray protons geophysical aspects of cosmic rays magnetic storms solar cosmic ray particles solar flares geomagnetic disturbance energy spectra storm sudden commencements solar flares proton flux increase sector boundary crossing }, mynotes={UNREAD}, } @ARTICLE{RastogiFeb76, title={ Equatorial E region electric field changes associated with a geomagnetic storm sudden commencement }, journal={Journal of Geophysical Research}, volume={81}, number={4}, year={1976}, month={Feb}, pages={687-9}, abstract={ The sudden commencement of geomagnetic storms occurring during daytime hours is shown to amplify or even to initiate equatorial ionospheric instabilities associated with the q type of sporadic-E layer and the scatter propagation of VHF radio waves. The negative impulse of a ssc-+ type of event is seen to be reproduced faithfully in the transequatorial VHF radio wave propagation, first as a sudden decrease of the signal strength and then as an increase. It is suggested that the enhancement of the H field over the magnetic equation during ssc events is due to the imposition of an additional electric field over the equatorial region, causing additional ssc-associated electrojet currents }, keywords={ atmospheric electricity E-region magnetic storms geomagnetic storm sudden commencement daytime equatorial ionospheric instabilities sporadic-E layer VHF radio wave propagation electrojet E-region electric field changes }, mynotes={UNREAD}, } @ARTICLE{HuangJan76, title={ Modeling HF Doppler effects of geomagnetic sudden commencements }, journal={Journal of Geophysical Research}, volume={81}, number={1}, year={1976}, month={Jan}, pages={175-82}, abstract={ A model has been proposed to explain the ionospheric effects of the sudden commencements as measured with a Doppler sounder. The model consists of different sources of electric fields generated in the ionosphere during the sudden commencement: a westward electromagnetically induced electric field generated in the F-region due to the change of magnetic field and an eastward dynamo electrostatic field set up in the dynamo region and transferred along the geomagnetic field lines to the F-region. The change of Doppler frequency shifts during the sudden commencement (ssc) is due to the vertical motion of the charged particles forced by these two opposing electric fields. The theoretical Doppler shifts were calculated on the basis of this model, and four observed ssc's and scf's were used to check the validity of the model }, keywords={ atmospheric electricity Doppler effect F-region ionosphere ionospheric electromagnetic wave propagation magnetic storms HF Doppler effects geomagnetic sudden commencements model ionospheric effects Doppler sounder electric fields F-region eastward dynamo electrostatic field westward EM induced field charged particles vertical motion }, mynotes={UNREAD}, } @ARTICLE{HoffmanNov75, author={Hoffman, R.A. and Maynard, N.C. and Smith, P.H. and Cahill, L.J. and Jr., Anderson and R.R., Fritz and T.A., Williams and D.J., Konradi and A. and Gurnett, D.A.}, title={ Explorer 45 (S/sup 3/-A) observations of the magnetosphere and magnetopause during the August 4-6, 1972, magnetic storm period }, journal={Journal of Geophysical Research}, volume={80}, number={31}, year={1975}, month={Nov}, pages={4287-96}, abstract={ The Explorer 45 (S/sup 3/-A) satellite performed extensive field and particle measurements in the heart of the magnetosphere during the double magnetic storm period of August 4-6, 1972. Both the ground level magnetic records and the magnetic field deformations measured along the orbit by the satellite indicated the existence of only a moderate ring current. This was confirmed by the measurements of the total proton energy density by the on-board particle detectors, which showed a maximum energy density less than the densities observed during the December 1971 and June 1972 magnetic storms. The plasmapause in the noon quadrant was eroded continuously from the onset of the first storm at the beginning of August 4 to an altitude below L=2.07 at about 1800 hours on August 5. Throughout the entire orbit during which the second sudden commencement occurred a large amount of low-frequency electric and magnetic field noise was encountered. The most remarkable observation during this orbit was the contraction of the magnetopause to distances inside the satellite location at L=5.2 }, keywords={ magnetic storms magnetosphere magnetosphere magnetopause magnetic storm period magnetic field deformations ring current magnetic field noise 1972 August 4 to 6 Explorer 45 satellite charged particle detection low frequency electric field noise }, mynotes={UNREAD}, } @ARTICLE{BerkoSep75, author={Berko, F.W. and Cahill, L.J. and Jr. and Fritz, T.A.}, title={ Protons as the prime contributors to storm time ring current }, journal={Journal of Geophysical Research}, volume={80}, number={25}, year={1975}, month={Sep}, pages={3549-52}, abstract={ Following a large sudden commencement on June 17, 1972, a large magnetic storm evolved, with a well-developed main phase and recovery phase. Explorer 45(S/sup 3/-A), with its apogee near 16 hours local time in June, measured the equatorial particle populations and magnetic field throughout this period. By use of data obtained during the symmetric recovery phase it is shown that through a series of self-consistent calculations, the measured protons, with energies from 1 to 872 keV, can account for almost all of the observed ring current magnetic effects within the limits of experimental uncertainties. This enables us to set an upper limit to the heavy ion contribution to the storm time ring current of a few percent of the proton contribution }, keywords={ atmospheric electricity magnetic storms magnetosphere sudden commencement magnetic storm equatorial particle populations magnetic field protons 1 to 872 keV ring current heavy ion contribution magnetosphere }, mynotes={UNREAD}, } @ARTICLE{VerschellApr75, author={Verschell, H.J. and Mendell, R.B. and Korff, S.A.}, title={ Two classes of cosmic ray decrease }, journal={Journal of Geophysical Research}, volume={80}, number={10}, year={1975}, month={Apr}, pages={1189-201}, abstract={ From an analysis of the time variations during 1968-1971 of the fast neutron flux in the upper atmosphere (mean energy response primaries, 1-2 GeV per nucleon) versus those of ground-based neutron monitors two classes of transient intensity decrease have been identified on the basis of differences in their spectral responses, time histories, and flare associations. Type 1 events are found to be classic Forbush decreases, sharp declines accompanying a geomagnetic storm sudden commencement following by 1-3 days a large optical flare with radio noise and energetic particle production, whereas type II events are more symmetric in their time histories and are therefore not associated with a particular flare. There are also differences in the spectral responses of the two types }, keywords={ cosmic ray neutrons cosmic ray variations galactic cosmic rays geophysical aspects of cosmic rays Forbush decrease primary cosmic rays solar flares spectral response fast neutron flux upper atmosphere transient intensity decrease geomagnetic storm sudden commencement }, mynotes={UNREAD}, } @ARTICLE{BasuAug74, title={ VHF ionospheric scintillations at L=2.8 and formation of stable auroral red arcs by magnetospheric heat conduction }, journal={Journal of Geophysical Research}, volume={79}, number={22}, year={1974}, month={Aug}, pages={3155-60}, abstract={ The 137-MHz amplitude scintillation data obtained from the ATS 3 satellite at a mid-latitude station (L=2.8) are utilized to study the temporal behavior of electron density irregularities following sudden commencements of intense magnetic storms. Comparison with the equatorial Dst index shows that the onset of scintillations is controlled by the universal time of commencement of the main and rapid recovery phases of storms. Total electron content data obtained simultaneously are used to show that the plasmapause-associated ionospheric trough moves to the vicinity of the observing point during the onsets of such universal time controlled scintillations. The magnetospheric heat conduction into the ionosphere during these storms, which sometimes causes stable auroral red arcs near the plasmapause, is found to produce field-aligned irregularities. A persistence of local time dominated scintillations following such storm time onsets is noted. The results of this study indicate that mid-latitude scintillations following large magnetic storms may have a storm time component in addition to the widely known local midnight component }, keywords={ aurora ionosphere ionospheric electromagnetic wave propagation magnetosphere radiowave propagation 137 MHz scintillation mid latitudes VHF ionospheric scintillations L stable auroral red arcs magnetospheric heat conduction ATS3 electron density irregularities sudden commencements intense magnetic storms equatorial Dst index plasmapause }, mynotes={UNREAD}, } @ARTICLE{BlakeApr74, author={Blake, J.B. and Martina, E.F. and Paulikas, G.A.}, title={ On the access of solar protons to the synchronous altitude region }, journal={Journal of Geophysical Research}, volume={79}, number={10}, year={1974}, month={Apr}, pages={1345-8}, abstract={ Observations of 10- to 90-MeV solar protons were made near the synchronous altitude around the time of a sudden commencement at 0037 UT on August 9, 1972, by using sensors aboard spacecraft 1970-93A and 1972-10A. The observations indicated that the solar protons had direct access to the synchronous altitude region through the dawn flank of the magnetosphere and were transiently trapped with an e-folding lifetime of a few drift periods. A weaker dependence of the cutoff energy upon local time was observed than was predicted by the calculations of Gall et al. (1971) }, keywords={ cosmic ray protons geophysical aspects of cosmic rays magnetosphere solar cosmic ray particles solar protons synchronous altitude region sudden commencement August 9, 1972 dawn flank magnetosphere cutoff energy local time 10 to 90 MeV }, mynotes={UNREAD}, } @ARTICLE{BlakeNov73, author={Blake, J.B. and Martina, E.F. and Paulikas, G.A.}, title={ On the access of solar protons to the synchronous altitude region }, journal={EOS Trans. Am. Geophys. Union (USA), EOS Transactions of the AmericanGeophysical Union}, volume={54}, number={11}, year={1973}, month={Nov}, pages={1182}, abstract={ Observations of 10-90 MeV solar protons were made near the synchronous orbit around the time of a sudden commencement on 9 August 1972 using sensors aboard 1970-93A and 1972-10A. The observations suggest that the protons had direct access to the synchronous region by entry through the dawn flank of the magnetosphere. The pitch-angle distributions of the solar protons indicate that the cutoff energies were substantially lower than predicted by trajectory calculations }, keywords={ magnetosphere sudden commencement magnetosphere cutoff energies trajectory calculations 10 to 90 MeV solar protons synchronous altitude region pitch angle distributions }, mynotes={UNREAD}, } @ARTICLE{AbduSep73, author={Abdu, M.A. and Ananthakrishnan, S. and Coutinho, E.F. and Krishnan, B.A. and Reis, E.M.S.}, title={ Azimuthal drift and precipitation of electrons into the South Atlantic geomagnetic anomaly during an SC magnetic storm }, journal={Journal of Geophysical Research}, volume={78}, number={25}, year={1973}, month={Sep}, pages={5830-6}, abstract={ Discusses an absorption event recorded by a 30-MHz riometer and also the VLF phase changes observed during a sudden commencement magnetic storm that occurred on August 4 to 5, 1972. The results provide evidence for the azimuthal drift and precipitation of electrons into the geomagnetic anomaly. Further evidence on the spatial nonuniformity in the particle precipitation is also presented }, keywords={ atmospheric electromagnetic wave propagation atmospheric electron precipitation geomagnetism magnetic storms radiowave propagation azimuthal drift South Atlantic geomagnetic anomaly SC magnetic storm absorption event VLF phase changes electron precipitation }, mynotes={UNREAD}, } @ARTICLE{BrownSep73, title={ Sudden commencement and sudden impulse absorption events at high latitudes }, journal={Journal of Geophysical Research}, volume={78}, number={25}, year={1973}, month={Sep}, pages={5698-702}, abstract={ Observations of sudden commencement absorption (SCA) and sudden impulse absorption events at the south pole (74.2 degrees invariant latitude) show that these events are concentrated on the dayside of the magnetosphere. Although the majority of the events were preceded by substorm activity in the midnight sector, SCA events were observed after prolonged magnetic quiet. This finding indicates the presence of a source, less conspicuous than sub-storm processes in the magnetotail, that supplies electrons in the region of quasi-trapping }, keywords={ magnetic storms sudden impulse absorption events high latitudes sudden commencement absorption south pole substorm activity midnight sector magnetotail electrons dayside magnetosphere }, mynotes={UNREAD}, } @ARTICLE{ArmstrongApr73, author={Armstrong, T.P. and Krimigis, S.M.}, title={ Time variations and angular distributions of alpha particles and medium nuclei for the October 27, 1972 solar particle events }, journal={EOS Trans. Am. Geophys. Union (USA), EOS Transactions of the AmericanGeophysical Union}, volume={54}, number={4}, year={1973}, month={Apr}, pages={410}, abstract={ Energy spectra and angular distributions of alpha particles and medium nuclei have been obtained with the JHU/APL experiment on Explorer 47 for the events which began on October 27, 1972. Analysis of preliminary data show that there exist short (a few minutes) and long (hours to days) term variations in the evolution of the alpha particle to medium nuclei (j/sub alpha //j/sub m/) intensity ratio at E approximately 2.6 MeV/nucleon. Specifically, the value of j/sub alpha //j/sub m/ increased from approximately 24 at approximately 1230 UT on October 30 to approximately 34 at 1500 UT on October 31, and reached a peak of approximately 150 at the time of the storm sudden commencement at approximately 1655 UT on the 31st before decreasing to approximately 22 on November 1 }, keywords={ cosmic ray alpha-particles and helium nuclei solar activity solar cosmic ray particles space vehicles October 27 1972 maximum flux sun minimum flux ionisation solar direction antisolar direction time variations angular distribution alpha particles medium nuclei solar particle event energy spectra Explorer 47 evolution nucleon storm }, mynotes={UNREAD}, } @ARTICLE{BrownApr73, title={ A study of ionospheric absorption in conjugate regions produced by storm sudden commencements and sudden impulses in the geomagnetic field }, journal={Journal of Geophysical Research}, volume={78}, number={10}, year={1973}, month={Apr}, pages={1668-72}, abstract={ Riometer data from Syowa, Antarctica, and Reykjavik, Iceland, were analyzed for the occurrence of sudden commencement (sc) and sudden impulse (si) absorption events over a 35-month period (February 1967 to December 1969). The results of this study include the fraction of sc and si that produce ionospheric absorption at L=6.3, the fraction of sc and si events that show absorption effects in conjugate regions, and the magnetic local time distributions of these events. The occurrence probability for conjugate events, plus other spatial features of these events, suggests a scale size of approximately 6*10/sup 4/ km for solar plasma at the boundary of the magnetosphere }, keywords={ geomagnetism ionospheric electromagnetic wave propagation magnetic storms solar plasma magnetosphere ionospheric absorption storm sudden commencements sudden impulses geomagnetic field ionospheric conjugate regions }, mynotes={UNREAD}, } @ARTICLE{PhillipsApr73, title={ Conjugate asymmetries in sudden commencement absorption and the sudden commencement absorption event of February 28, 1969 }, journal={Journal of Geophysical Research}, volume={78}, number={10}, year={1973}, month={Apr}, pages={1563-71}, abstract={ A balloon observation of sudden commencement X-rays (up to 2 times background) was made near Macquarie Island ( lambda =-61 degrees ) at 0423 UT on February 28, 1969. A synoptic study of this event, using riometer data, reveals that in the morning sector of the auroral zone the pattern of sudden commencement absorption (sca) is similar to that inferred from previous statistical studies. The situation in the afternoon sector is not clear. The sca at College was 10 times greater than that at Macquarie Island, and thus an asymmetry in sca between stations occupying positions of near conjugacy is indicated. A restricted period of data from the conjugate stations Great Whale River and Byrd reveals two other asymmetrical sca events. It is suggested that asymmetries in conjugate sca, and perhaps variations in the longitudinal distribution of sca, occur when a solar wind shock normal makes a large angle with the geomagnetic equatorial plane or the sun-earth line }, keywords={ cosmic ray X-rays geomagnetism geophysical aspects of cosmic rays conjugate asymmetries sudden commencement absorption sudden commencement X-rays Macquarie Island riometer data auroral zone Great Whale River solar wind shock geomagnetic equatorial plane sudden commencement absorption event February 28 1969 }, mynotes={UNREAD}, } @ARTICLE{KoonsJul72, author={Koons, H.C. and McPherson, D.A.}, title={ Observation of very-low-frequency whistler-mode waves in the region of the radiation-belt slot }, journal={Journal of Geophysical Research}, volume={77}, number={19}, year={1972}, month={Jul}, pages={3475-82}, abstract={ Following a sudden-commencement magnetic storm, band-limited VLF emissions between 3.9 and 10.4 kHz were observed at high altitudes within the plasmasphere (L approximately 2.5 to 3.6) by a receiver aboard spacecraft OV1-14 (1968-26B). The maximum spectral intensities of 1.1 m gamma /Hz/sup 1/2/ and 2.8 mu v/Hz/sup 1/2/ on the magnetic and electric antennas, respectively, occur in the 5.6-kHz channel. The waves can resonantly interact with energetic electrons above approximately 50 kev at L=2.5, and the measured wave intensities are sufficiently high to account for the short lifetimes of medium-energy electrons in the slot region between the inner and outer Van Allen radiation zones. A comparison with ground-based VLF data suggests that the waves are generated by band-limited amplification of incoherent noise }, keywords={ magnetic storms radiation belts whistlers incoherent noise maximum spectral intensities VLF whistler mode waves radiation belt slot sudden commencement magnetic storm medium energy electrons OV1 14 (1968 26B) }, mynotes={UNREAD}, } @ARTICLE{BrownOct72, author={Brown, R.R. and Leinbach, H. and Akasofu, S.-I. and Driatsky, V.M. and Schmidt, R.J.}, title={ Quadruple conjugate pair observations of the sudden commencement absorption event on June 17, 1965 }, journal={Journal of Geophysical Research}, volume={77}, number={28}, year={1972}, month={Oct}, pages={5602-7}, abstract={ Sudden commencement absorption at 2144 UT, June 17, 1965, was observed with two groups of conjugate riometers separated by approximately 100 degrees in magnetic longitude. The location of the region of maximum precipitation occurred in the local afternoon hours. From closely spaced riometers in the midnight sector, evidence is presented indicating that the triggering of magnetospheric substorms by sudden commencements is highly structured }, keywords={ ionosphere magnetic storms magnetosphere ionospheric absorption electron precipitation magnetospheric electrons quadruple conjugate pair observations sudden commencement absorption June 17, 1965 conjugate riometers magnetospheric substorms }, mynotes={UNREAD}, } @ARTICLE{EvansMay72, title={ Measurements of horizontal drifts in the E and F regions at Millstone Hill }, journal={Journal of Geophysical Research}, volume={77}, number={13}, year={1972}, month={May}, pages={2341-52}, abstract={ At Millstone Hill (42.6 degrees N, 71.5 degrees W) an oblique-incidence incoherent-scatter radar system has been employed to observe the drift of the ionospheric plasma in the E and F regions in directions across the earth's magnetic field. These measurements yield the true macroscopic motion of the ions rather than the motion of waves impressed in the plasma, but, owing to sensitivity limitations, measurements could be made only during the daytime when the electron density is large. It is found that the drift appears to be independent of altitude above about 180 km; this result suggests that the drift is caused by an electrostatic field. On the average the drift has an amplitude of about 25 m/sec (1 mv/m), and the direction rotates in a clockwise sense through 360 degrees in 12 hours. The drifts observed at 130 km appear similar to the drifts in the F region, but in azimuth the direction lags behind the drift observed in the F region by 50 degrees -60 degrees . It appears that the electric field responsible for the drift in the F region is generated in the E region by the dynamo action of the solar semidiurnal (2,2) tidal oscillation. On one day electric fields of magnetospheric origin developed following a magnetic storm sudden commencement. The clockwise progression of the drift was then reversed, and the drift reached 200 m/sec toward the west. This motion may be connected with the reported sunward surges of the plasma in the plasmasphere bulge at times of substorms }, keywords={ E-region F-region ionospheric measurement E-region solar semidiurnal tidal oscillation horizontal drifts Millstone Hill radar system ionospheric plasma macroscopic motion daytime electrostatic field magnetic storm sudden commencement F-region }, mynotes={UNREAD}, } @ARTICLE{MontgomeryApr72, author={Montgomery, M.D. and Asbridge, J.R. and Bame, S.J. and Feldman, W.C.}, title={ Positive evidence for closed magnetic structures in the solar wind associated with interplanetary shock waves }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={53}, number={4}, year={1972}, month={Apr}, pages={503}, abstract={ It has been suggested by a number of investigators that magnetic loops carried into the solar wind with solar flare ejecta may later merge near the sun forming closed magnetic 'bottles.' Solar wind electrons are normally in good thermal contact with the solar corona due to the high thermal conductivity of the interplanetary medium along the magnetic field. Thus the electron temperature T/sub e/ and 1 AU is normally relatively constant. However, formation of a magnetic bottle would thermally isolate the electrons within, permitting them to cool relatively quickly as the bottle expands. Positive evidence for this effect has been found from a study of 11 months of Vela 5, Vela 6, and IMP-6 solar wind plasma data during parts of 1969, 1970, and 1971. Eleven periods of depressed temperatures lasting 1 to 3 days were found where T/sub e/ reached the lowest measurable value ( approximately 5*10/sup 4/ degrees K): much below the 1-2*10/sup 5/ degrees K average. All 11 cases were preceded by an observed IP shock and/or a well defined sudden commencement. Of the 21 SC's that occurred during the period of study, 17 were followed by sufficient observations. Of these, 11 were followed by clear, deep depressions in T/sub e/, 3 by shallower depressions, and 3 by none. The decrease in T/sub e/ typically follows the shock passage by 4-18 hr. For the one case when the He concentration is so far available, a threefold rise in HE/H was observed. T/sub p/ is also found to be somewhat depressed during the same periods }, keywords={ interplanetary matter plasma confinement shock waves solar corpuscular radiation closed magnetic structures solar wind interplanetary shock waves magnetic loops solar flare ejecta magnetic bottle wind plasma data }, mynotes={UNREAD}, } @ARTICLE{BurnsJan72, author={Burns, A.L. and Krimigis, S.M.}, title={ Changes in the distribution of low-energy trapped protons associated with the April 17, 1965, magnetic storm }, journal={Journal of Geophysical Research}, volume={77}, number={1}, year={1972}, month={Jan}, pages={112-30}, abstract={ The absolute intensity of geomagnetically trapped protons in the energy ranges 0.52or approximately=2.5 and all sampled mod B mod ranges, which persisted for at least 36 days after the storm. The effect of the sudden commencement was a general depression in the intensities and a hardening of the energy spectrums, although the intensities recovered to their prestorm level during the initial phase. The major redistribution was apparently initiated by the polar substorm that began at approximately 0620 UT on April 18 and continued long after (to 1100 UT) the substorm had subsided ( approximately 0800 UT). During the recovery phase, a secondary peak developed in the intensity profile at L approximately 3.5 for 0.52-Mev protons that had no counterpart at this energy at the equator (L.R. Davis, private communication, 1971). No such peak was observed for 0.9-Mev protons. The over-all effect of the storm on the steady-state distribution was a nonadiabatic one with an increase in intensities at L70/cm/sup 3/) were encountered, and, when the flux decreased by a moderate factor, large-amplitude 70-kHz noise bursts were sporadically detected on the VLF electric and magnetic sensors. The authors interpret the oscillations with correlated E and B components as electromagnetic waves that have n/sup 2/ approximately=1- omega /sub p//sup 2// omega /sup 2/<1, and direct comparison with the plasma probe density estimate gives an absolute calibration for that instrument. The measured wave amplitudes are also used to evaluate the local density from the relation n=cB/E, thus leading to an absolute calibration for the electric dipole within the streaming plasma. They find that all measured or deduced densities are in agreement and are compatible with the interpretation that the correlated noise bursts represent electromagnetic waves with omega near the local plasma resonance frequency. These observations are related to previous measurements of 20- to 30-kHz electric fields in the solar wind, and the problem of distinguishing between electromagnetic waves of this type and electrostatic plasma oscillations is considered }, keywords={ electromagnetic waves solar corpuscular radiation }, mynotes={UNREAD}, } @ARTICLE{RobbinsMar70, author={Robbins, D.E. and Hundhausen, A.J. and Bame, S.J.}, title={ Helium in the solar wind }, journal={Journal of Geophysical Research}, volume={75}, number={7}, year={1970}, month={Mar}, pages={1178-87}, abstract={ Data obtained from electrostatic analyzers on the Vela 3A and 3B satellites from July 1965 to July 1967 have been analyzed to obtain relative helium abundances and plasma properties. Large variations in the helium to hydrogen density ratio were observed even when averaged over a solar rotation. Sudden increases in the solar wind helium content followed simultaneous occurrences of Forbush decreases and sudden-commencement geomagnetic storms. The magnitude of the helium to hydrogen density ratio, however, was not correlated to the magnitude of the geomagnetic storm, as measured by the Kp index. The ratio of the helium to hydrogen velocities was strongly peaked around 1.0, as might be expected }, keywords={ helium solar corpuscular radiation }, mynotes={UNREAD}, } @ARTICLE{EvansOct69, author={Evans, L.C. and Stone, E.C.}, title={ Access of solar protons into the polar cap: a persistent north-south asymmetry }, journal={Journal of Geophysical Research}, volume={74}, number={21}, year={1969}, month={Oct}, pages={5127-31}, abstract={ Before the magnetic storm sudden commencement during the 2 Nov 1967 solar particle event, the access of 1.2- to 40-MeV protons into the high-latitude portion of the northern polar region was delayed by approximately 20 hours. At the same time the access delay for 10- to 40-MeV protons was 3 MeV measured by SAMPEX disappear for over 12 hours at the beginning of November 4. This represents a 3 orders of magnitude decrease down to the cosmic ray background of the detector. GPS and LANL sensors show similar effects, confirming that the flux drop of the energetic electrons occurs near the magnetic equator and at all pitch angles. Enhanced electron precipitation was measured by SAMPEX at L>or=3.5. The outer zone electron fluxes then recover and exceed prestorm levels within one day of the storm onset and the inner boundary of the outer zone moves inward to smaller L (<3). These multiple-satellite measurements provide a data set which is examined in detail and used to determine the mechanisms contributing to the loss and recovery of the outer zone electron flux. The loss of the inner part of the outer zone electrons is partly due to the adiabatic effects associated with the decrease of Dst, while the loss of most of the outer part (those electrons initially at L>or=4.0) are due to either precipitation into the atmosphere or drift to the magnetopause because of the strong compression of the magnetosphere by the solar wind. The recovery of the energetic electron flux is due to the adiabatic effects associated with the increase in Dst, and at lower energies (<0.5 MeV) due to rapid radial diffusion driven by the strong magnetic activity during the recovery phase of the storm. Heating of the e }, keywords={ magnetic storms magnetosphere radiation belts magnetosphere radiation belt AD 1993 11 03 AD 1993 11 04 outer zone electron variation magnetic storm energetic electrons SAMPEX GPS relativistic electron flux decrease enhanced electron precipitation radial diffusion }, mynotes={UNREAD}, } @ARTICLE{NakamuraMay97, author={Nakamura, R. and Kokubun, S. and Mukai, T. and Yamamoto, T.}, title={ Changes in the distant tail configuration during geomagnetic storms }, journal={Journal of Geophysical Research}, volume={102}, number={A5}, year={1997}, month={May}, pages={9587-601}, abstract={ Changes in the structure of the distant tail associated with geomagnetic storms are studied by using plasma and magnetic field data obtained from Geotail. Thirteen storm intervals between October 1993 and October 1994 are examined when the satellite was located in the distant tail between X=-83 R/sub E/ and X=-210 R/sub E/. Geotail observed the magnetosheath during all storms including those when the satellite was located near the nominal tail axis. Assuming the flow direction in the magnetosheath to be parallel to the magnetotail axis, the authors estimated the dimension and the flux of the tail for the magnetopause crossing events. Systematic changes of the distant tail structure are found in association with the development of the storms. Before the main phase onset of the storms, when the Dst shows positive excursion, the enhanced solar wind pressure reduces the average radius of the distant tail to \23 R/sub E/ as compared with the quiet time value, \31 R/sub E/. During the storm main phase the dimension of the tail is comparable to the quiet time value in spite of the high solar wind pressure. This is attributed to the enhanced magnetic flux in the tail in association with the southward interplanetary magnetic field (IMF) B/sub z/. An average energy of \5*10/sup 15/ J is stored also in the distant tail during the storm main phase, which is a comparable value to that stored in the midtail during an intense substorm growth phase reported in the previous studies. During storm time, when the B/sub z/ component of the magnetosheath field was larger compared with the By component, the average tail cross section has a north-south elongated elliptical shape. The average tail for quiet time, however, was elongated toward the dawn-dusk direction. By component was larger than B/sub z/ component in their quiet time data set. These observations imply that the anisotropy in the magnetosheath magnetic field pressure for different IMF orientation changes the shape of the tail }, keywords={ magnetic storms magnetosphere magnetosphere distant tail configuration change magnetotail geomagnetic storm magnetic storm substorm magnetic field data plasma observations Geotail AD 1993 AD 1994 distant tail magnetosheath magnetopause crossing event positive excursion Dst 83 to 210 Earthradii }, mynotes={UNREAD}, } @ARTICLE{ShiokawaSep96, author={Shiokawa, K. and Yumoto, K. and Meng, C.-I. and Reeves, G.}, title={ Broadband electrons observed by the DMSP satellites during storm-time substorms }, journal={Geophysical Research Letters}, volume={23}, number={18}, year={1996}, month={Sep}, pages={2529-32}, abstract={ Electrons that have intense broadband spectra, are found to precipitate in the equatorward part of the auroral oval. The electrons are observed by the DMSP satellites in association with particular substorms during the main phase of magnetic storms. Electron fluxes are drastically enhanced after the substorm onset at all the energies measured (32 eV to 30 keV) at magnetic latitudes lower than 60 degrees (L<4). The energy flux of the electrons exceeds 1.0*10/sup 13/ eV cm/sup -2/s/sup -1/sr/sup -1/. The intense electron precipitation lasts less than 1 h. These characteristics are significantly different from those seen in the central plasma sheet region. The authors suggest that an unknown energization mechanism of these electrons exists at the inner part of the plasma sheet at L<4 during these particular storm-time substorms }, keywords={ atmospheric electron precipitation magnetic storms magnetosphere radiation belts ionosphere magnetosphere radiation belt electron precipitation magnetic storm substorm broadband electrons DMSP satellite intense broadband spectra intense electron precipitation plasma sheet magnetotail 30 eV to 32 keV }, mynotes={UNREAD}, } @ARTICLE{ValdiviaOct96, author={Valdivia, J.A. and Sharma, A.S. and Papadopoulos, K.}, title={ Prediction of magnetic storms by nonlinear models }, journal={Geophysical Research Letters}, volume={23}, number={21}, year={1996}, month={Oct}, pages={2899-902}, abstract={ The strong correlation between magnetic storms and southward interplanetary magnetic field (IMF) is well known from linear prediction filter studies using the Dst and IMF data. However, the linear filters change significantly from one storm to another and thus are limited in their predicting ability. Previous studies have indicated nonlinearity in the magnetospheric response as the ring current decay rate varies with the Dst value during storms. The authors present in this letter nonlinear models for the evolution of the Dst based on the OMNI database for 1964-1990. When solar wind data are available in advance, the evolution of storms can be predicted from the Dst and IMF data. Solar wind data, however, are not available most of the time or are available typically an hour or less in advance. Therefore. They have developed nonlinear predictive models based on the Dst data alone. In the absence of solar wind data, these models cannot predict the storm onset, but can predict the storm evolution, and may identify intense storms from moderate ones. The input-output model based on IMF and Dst data, the autonomous model based on Dst alone, and a combination of the two call be used as forecasting tools for space weather }, keywords={ magnetic storms AD 1964 to 1990 forecasting prediction magnetic storm solar wind magnetosphere interaction nonlinear model southward interplanetary magnetic field IMF direction Dst nonlinear predictive model onset storm evolution intense storm input-output model }, mynotes={UNREAD}, } @ARTICLE{TanakaAug96, author={Tanaka, T. and Ohtaka, K.}, title={ Ionospheric disturbances during low-latitude auroral events and their association with magnetospheric processes }, journal={Journal of Geophysical Research}, volume={101}, number={A8}, year={1996}, month={Aug}, pages={17151-9}, abstract={ Ionospheric disturbances associated with low-latitude auroral events that occurred during geomagnetic storms on October 21, 1989, and May 10, 1992, are investigated from measurements of the total electron content (TEC) by the U.S. Navy Navigation Satellite System (NNSS) and ionosonde data from the Japanese meridian chain. Features of the ionospheric disturbances are then associated with the progression of geomagnetic disturbances during the storms. After the onset of the main phase of each storm, anomalous TEC distributions characterized by depressed TEC distributions on the high-latitude side (>35 degrees geographic latitude) and an enhanced equatorial ionization anomaly (EIA) on the low-latitude side (<35 degrees geographic latitude) were observed over Japan both by the NNSS and by the meridian chain of ionosonde stations. This enhancement of the EIA suggests the penetration of magnetospheric electric fields during the storms. Corresponding to the anomalous TEC decreases in the northern part of Japan, ionosonde stations in this region observed specific disturbances of ionospheric variation characterized by simultaneous decreases of f/sub 0/F/sub 2/ and increases of h'F. These features of ionospheric variations on the high-latitude side can be attributed to the upward escape of ionospheric plasma caused by the heating and evacuation mechanisms, which are induced by depletion of the plasmasphere and the resulting access of ring current particles to low latitudes }, keywords={ aurora ionospheric disturbances magnetic storms magnetosphere ionospheric disturbances low-latitude auroral events magnetospheric processes geomagnetic storms AD 1989 10 21 AD 1992 05 10 total electron content US Navy Navigation Satellite System NNSS ionosonde data Japanese meridian chain geomagnetic disturbances anomalous TEC equatorial ionization anomaly magnetospheric electric field penetration F/sub 2/-layer critical penetration frequency ionospheric variations ionospheric plasma escape plasma heating plasmasphere ring current particles }, mynotes={UNREAD}, } @ARTICLE{MurphyDec95, author={Murphy, J.R. and Pollack, J.B. and Haberle, R.M. and Leovy, C.B. and Toon, O.B. and Schaeffer, J.}, title={ Three-dimensional numerical simulation of Martian global dust storms }, journal={Journal of Geophysical Research}, volume={100}, number={E12}, year={1995}, month={Dec}, pages={26357-76}, abstract={ Presents results from the first numerical simulations of simultaneously evolving three-dimensional thermal, dynamical, and radiatively active suspended dust fields in the Martian atmosphere. Simulations of southern summer dust storms (arising from a prescribed southern subtropical surface dust source) conducted with a Mars general circulation model (GCM) illustrate the important role of dust transport by atmospheric eddies. Both traveling and stationary eddies contribute to dust transport, to high latitudes in both hemispheres. These hemispheric differences arise from seasonal and topographic effects. Transport into the south polar regions is accomplished primarily by thermally and topographically forced standing eddies. Both traveling and stationary eddies transport dust to middle and high northern (winter) latitudes. Atmospheric wave motions are affected by the developing storms. Thermal tidal amplitudes increase at storm onset, with the calculated pressure response at a model grid point corresponding to the location of the Viking Lander 1 site in good agreement with observations. In qualitative agreement with observations, winter hemisphere baroclinic waves weaken during the early stages of the storm, but as the storm wanes, amplitudes of these waves increase. A slowly westward propagating (9 degrees of longitude per sol) zonal wavenumber one feature in the temperature and geopotential fields at middle northern latitudes amplifies rapidly during the initial sols (Martian solar days) of the simulated storms. This feature is suggestive of the observed north polar warming which occurred during the 1977B global dust storm, but the simulations produce a much weaker polar warming (À10 K at 0.5 mbar) than was observed (40-50 K). The globally integrated CO/sub 2/ condensation rate decreases by 15-20% during the simulated dust storm onset and would likely be decreased more if a stronger polar warming were produced. During the initial stages of the simulated storms, surfac }, keywords={ cosmic dust Mars planetary atmospheres planetary surfaces storms Mars planet atmosphere global dust storm dust transport planet surface tree-dimensional model numerical simulation suspended dust atmosphere southern summer dust storms general circulation model GCM eddies winter hemisphere baroclinic wave polar warming }, mynotes={UNREAD}, } @ARTICLE{McEwenOct95, author={McEwen, D.J. and Huang, K.}, title={ The polar onset and development of the November 8 and 9, 1991, global red aurora }, journal={Journal of Geophysical Research}, volume={100}, number={A10}, year={1995}, month={Oct}, pages={19585-94}, abstract={ On November 8, 1991, a major magnetic storm began with a sudden commencement at 0647 UT; it continued until about 1800 UT on November 9. Associated with this storm there was a great aurora which continued through November 8 and until at least 1200 UT on November 9. The first optical indication of this event was the appearance of bright Sun-aligned arcs over Eureka, North West Territories (89 degrees corrected geomagnetic latitude (CGM)), Canada from 0750 UT until about 1230 UT on November 8. By that time, there was a gradual transformation to dominant 6300 AA emission over the central polar cap. Gradually, the major soft electron precipitation and associated red aurora moved equatorward. The aurora reached a low-latitude limit of 40 degrees CGM at 0600 UT on November 9. The polar arcs reached 22 kR intensity (5577 AA), while the red aurora seen later at low latitudes was at least 100 kR (6300 AA). The analysis of Defense Meteorological Satellite Program (DMSP) particle data from 83 passes during November 8 and 9 showed the extent and movement of precipitation from the polar region to midlatitudes. A comparison of this event was made with the earlier great auroral event of March 13-14, 1989. While the extent in low latitude and the duration of the two disturbances were similar, the November 8-9 event had approximately one half of the total energy input into the ionosphere. Its striking and unusual feature was the auroral onset and activity in the central polar region, a feature possibly related to the solar wind interplanetary magnetic field orientation }, keywords={ aurora magnetic storms AD 1991 11 08 to 09 global red aurora polar onset development major magnetic storm sudden commencement bright Sun-aligned arcs central polar cap soft electron precipitation polar arcs Defense Meteorological Satellite Program DMSP particle data visible disturbances ionospheric energy input solar wind interplanetary magnetic field orientation 557.7 nm 630 nm O }, mynotes={UNREAD}, } @ARTICLE{FejerApr95, author={Fejer, B.G. and Scherliess, L.}, title={ Time dependent response of equatorial ionospheric electric fields to magnetospheric disturbances }, journal={Geophysical Research Letters}, volume={22}, number={7}, year={1995}, month={Apr}, pages={851-4}, abstract={ Uses extensive radar measurements of F-region vertical plasma drifts and auroral electrojet indices to determine the storm time dependence of equatorial zonal electric fields. These disturbance drifts result from the prompt penetration of high latitude electric fields and from the dynamo action of storm time winds which produce largest perturbations a few hours after the onset of magnetic activity. The signatures of the equatorial disturbance electric fields change significantly depending on the relative contributions of these two components. The prompt electric field responses, with lifetimes of about one hour, are in excellent agreement with results from global convection models. The electric fields generated by storm time winds have longer lifetimes, amplitudes proportional to the energy input into the high latitude ionosphere, and a daily variation which follows closely the disturbance dynamo pattern of Blanc and Richmond (1980). The storm wind driven electric fields are responsible for the larger amplitudes and longer lifetimes of the drift perturbations following sudden decreases in convection compared to those associated with sudden convection enhancements }, keywords={ F-region ionospheric disturbances ionosphere magnetosphere interaction time dependent response equatorial ionosphere electric field magnetospheric disturbance F-region vertical plasma drift auroral electrojet index storm time dependence equatorial zonal electric fields. penetration dynamo action global convection model daily variation }, mynotes={UNREAD}, } @ARTICLE{RichardsDec94, author={Richards, P.G. and Torr, D.G. and Buonsanto, M.J. and Sipler, D.P.}, title={ Ionospheric effects of the March 1990 magnetic storm: comparison of theory and measurement }, journal={Journal of Geophysical Research}, volume={99}, number={A12}, year={1994}, month={Dec}, pages={23359-65}, abstract={ Presents a comparison of the measured and modeled ionospheric response to magnetic storms at Millstone Hill and Arecibo during March 16-23, 1990. Magnetic activity was low until midday UT on day 18 when Kp reached 6, days 19 and 20 were quiet, but a large storm occurred around midnight UT on day 20 (Kp=7) and it was moderately disturbed (Kp=4) for the remainder of the study period. At Millstone Hill, the daytime peak electron density (NmF/sub 2/) showed only a modest 30% decrease in response to the first storm and recovered to prestorm values before the onset of the second storm. The model reproduces the daytime peak electron density well for this period. However, the severe storm on March 20 caused a factor of 4 depletion in electron density, while the model densities were not greatly affected. The inclusion of vibrationally excited nitrogen (N/sub 2//sup */) in the model was unable to account for the observed large electron density depletions after March 20. The storm did not appear to affect the overall magnitude of the electron density at Arecibo very much, but did cause unusual wavelike structure in the peak density and peak height following the storm. The model reproduces the daytime NmF/sub 2/ very well for Arecibo, but after sunset the model densities decay too rapidly. This study indicates that successful modeling of severe ionospheric storms will require better definition of the storm time inputs, especially of the neutral atmosphere }, keywords={ electron density ionospheric disturbances magnetic storms ionospheric effects AD 1990 03 16 to 23 magnetic storms Millstone Hill Arecibo magnetic activity Kp index model daytime peak electron density vibrationally excited N/sub 2//sup */ wavelike structure severe ionospheric storms }, mynotes={UNREAD}, } @ARTICLE{YehApr94, author={Yeh, K.C. and Ma, S.Y. and Lin, K.H. and Conkright, R.O.}, title={ Global ionospheric effects of the October 1989 geomagnetic storm }, journal={Journal of Geophysical Research}, volume={99}, number={A4}, year={1994}, month={Apr}, pages={6201-18}, abstract={ Based on a large data base from 40 ionosonde stations distributed worldwide and 12 total electron content stations, a case study is made on the global behavior of ionospheric responses to the great magnetic storm of October 1989. The magnetic storm was triggered by a solar flare with the largest class of X13/4B and started with a sudden storm commencement (ssc) at 0917 UT on October 20. After the initial phase the storm underwent two periods of maximum activities in the following 2 days. Low-latitude auroras were sighted and reported in widely separated areas in both northern and southern hemispheres. In response to these magnetic and auroral activities the ionosphere showed remarkable effects. Depending on the local time of ssc occurrence, the ionospheric response differed appreciably. Impressive changes were long-lasting, large-scale effects, such as the severe depressions of foF2 at higher latitudes, the temporary suppression of the equatorial anomaly and large horizontal gradients at certain latitudes. Also observed were positive storm effects of short duration during the post-sunset period in response to the onset of both ssc and main phase of the magnetic storm. These two positive storm effects showed different patterns suggesting different causal mechanisms. In addition, global propagation of large-scale traveling ionospheric disturbances (TIDs) was seen during 2 nights, identified by dramatic rises of h'F with periodic fluctuations }, keywords={ ionosphere magnetic storms AD 1989 10 ionosphere disturbance global effect magnetic storm geomagnetic storm sudden storm commencement ssc SSC ionospheric response severe depression low latitude aurora F-region critical frequency equatorial anomaly travelling ionospheric disturbance traveling ionospheric disturbance TID }, mynotes={UNREAD}, } @ARTICLE{Fuller-RowellMar94, author={Fuller-Rowell, T.J. and Codrescu, M.V. and Moffett, R.J. and Quegan, S.}, title={ Response of the thermosphere and ionosphere to geomagnetic storms }, journal={Journal of Geophysical Research}, volume={99}, number={A3}, year={1994}, month={Mar}, pages={3893-914}, abstract={ Four numerical simulations have been performed, at equinox, using a coupled thermosphere-ionosphere model, to illustrate the response of the upper atmosphere to geomagnetic storms. The storms are characterized by an increase in magnetospheric energy input at high latitude for a 12-hour period; each storm commences at a different universal time (UT). The initial response at high latitude is that Joule heating raises the temperature of the upper thermosphere and ion drag drives high-velocity neutral winds. The heat source drives a global wind surge, from both polar regions, which propagates to low latitudes and into the opposite hemisphere. The surge has the character of a large-scale gravity wave with a phase speed of about 600 m s/sup -1/. Behind the surge a global circulation of magnitude 100 m s/sup -1/ is established at middle latitudes, indicating that the wave and the onset of global circulation are manifestations of the same phenomena. A dominant feature of the response is the penetration of the surge into the opposite hemisphere where it drives poleward winds for a few hours. The global wind surge has a preference for the night sector and for the longitude of the magnetic pole and therefore depends on the UT start time of the storm. A second phase of the meridional circulation develops after the wave interaction but is also restricted, in this case by the buildup of zonal winds via the Coriolis interaction. Conservation of angular momentum may limit the buildup of zonal wind in extreme cases. The divergent wind field drives upwelling and composition change on both height and pressure surfaces }, keywords={ atmospheric movements ionosphere thermosphere upper atmosphere numerical model simulation equinox coupled thermosphere ionosphere model response upper atmosphere geomagnetic storm magnetic storm magnetospheric energy input ion drag global wind surge large-scale gravity wave global circulation surge meridional circulation zonal wind Coriolis interaction conservation of angular momentum wind disturbance }, mynotes={UNREAD}, } @ARTICLE{DelcourtJan94, author={Delcourt, D.C. and Sauvaud, J.A.}, title={ Plasma sheet ion energization during dipolarization events }, journal={Journal of Geophysical Research}, volume={99}, number={A1}, year={1994}, month={Jan}, pages={97-108}, abstract={ The energization of plasma sheet particles during storm-time dipolarization of the magnetospheric field lines is examined by means of 3D particle codes. In the direction perpendicular to the magnetic field, owing to appreciable temporal variations of the field within a cyclotron turn, particles can experience large magnetic moment changes. A detailed analysis of this effect reveals an "effective pick-up velocity" at substorm onset, which depends upon the magnitude of the magnetic transition and delineates particle motions at nearly constant or highly variable magnetic moment. In the parallel direction, the large but short-lived electric field yields an intense acceleration of the particles traveling in the equatorial region. It is demonstrated that significant decelerations can also be achieved off-equator if the particles drift against the surging electric field. Such decelerations occur in regions where the curvature of the E*B paths substantially exceeds that of the magnetic field lines. Systematic calculations of model plasma sheet distribution functions clearly exemplify the earthward injection of energetic particles during dipolarization events. Owing to phasing between particle motion and the transient electric field, the computed spectrograms display the formation of characteristic bouncing ion patterns with fine structures on fast time scales. To some extent, the simulations support the convection surge mechanism of particle acceleration put forward by Mauk (1986). However, distinct collapse characteristics as well as the inclusion of nonadiabatic effects result in significantly higher energization rates, particularly at high mass-to-charge ratios }, keywords={ atmospheric elementary particle precipitation geomagnetism magnetic storms magnetosphere plasma plasma sheet particles energization storm-time dipolarization magnetospheric field lines 3D particle codes magnetic moment changes effective pick-up velocity substorm onset magnetic transition perpendicular direction parallel direction electric field acceleration equatorial region particle drift deceleration E*B paths curvature earthward injection bouncing ion patterns convection surge mechanism collapse characteristics nonadiabatic effects }, mynotes={UNREAD}, } @ARTICLE{UllalandSep93, author={Ullaland, S. and Kremser, G. and Tanskanen, P. and Korth, A. and Roux, A. and Torkar, K. and Block, L.P. and Iversen, I.B.}, title={ On the development of a magnetospheric substorm influenced by a storm sudden commencement: ground, balloon, and satellite observations }, journal={Journal of Geophysical Research}, volume={98}, number={A9}, year={1993}, month={Sep}, pages={15381-401}, abstract={ Discusses a relationship between storm sudden commencements (ssc) and magnetospheric substorm onsets. The authors used a comprehensive data set for a detailed case study. The ssc occurred on July 6, 1979, at 1930 UT. The substorm expansion phase started 5 min later. The event was preceded by a loading phase of more than 1.5 hours. The loading phase developed in three steps. During each step the cross-tail current sheet suddenly expanded earthward and intensified. The third step, at 1930 UT, coincided with the ssc. It was very likely caused by the interaction of ions with magnetohydrodynamic waves generated by the ssc. This step was followed at 1935 UT by the onset of the expansion phase accompanied by PiB magnetic pulsations, impulsive electron precipitation, and energetic ion injection at GEOS 2 orbit. The dipolarization of the geomagnetic field started 9 min after the expansion phase onset together with energetic electron injection and a decrease in the energetic ion flux. Signatures of Birkeland currents at dipolarization, and a pressure anisotropy P/sub //ions/ > P/sub perpendicular to ions/ during the 4 min before dipolarization, indicate field-aligned processes consistent with partial diversion of the cross-tail current into the ionosphere. The observations are discussed in the framework of a model in which the ballooning mode instability (BMI) developing in the near-Earth plasma sheet is regarded as the trigger process for the expansion phase }, keywords={ atmospheric electricity atmospheric electron precipitation magnetic storms micropulsations plasma magnetospheric substorm storm sudden commencement substorm onsets expansion phase loading phase cross-tail current sheet magnetohydrodynamic waves AD 1979 07 06 PiB magnetic pulsations impulsive electron precipitation energetic ion injection dipolarization geomagnetic field energetic ion flux Birkeland currents pressure anisotropy field-aligned processes ionosphere ballooning mode instability near-Earth plasma sheet trigger }, mynotes={UNREAD}, } @ARTICLE{GalperinNov92, author={Galperin, Y.I. and Volosevich, A.V. and Zelenyi, L.M.}, title={ Pressure gradient structures in the tail neutral sheet as 'roots of the arcs' with some effects of stochasticity }, journal={Geophysical Research Letters}, volume={19}, number={21}, year={1992}, month={Nov}, pages={2163-6}, abstract={ Westward cross-tail current at the earthward edge of the plasma sheet is enhanced due to strongly stochastic (r/sub Li/ approximately R/sub c/) ion motions. A narrow elongated magnetic field depression arises which leads to further stochastication of the ions convecting through it, and to a local increase of magnetostatic plasma pressure, enhanced lateral transport and removal of higher energy ions. This plasma structure can be stationary in the magnetospheric frame. It is the 'root' of sheet-like auroral currents of stable auroral homogeneous arcs/bands (inverted-V's) located at the equatorial edge of the steady premidnight auroral oval. The magnetic field minimum can be the location of a sub-storm onset when it deepens below the stability threshold for reconnection/tearing }, keywords={ magnetosphere roots of the arcs magnetosphere magnetotail magnetic tail pressure gradient structure westward cross tail current stochastic ion motion neutral sheet stochasticity plasma sheet narrow elongated magnetic field depression magnetostatic plasma pressure enhanced lateral transport }, mynotes={UNREAD}, } @ARTICLE{BurnsMay92, author={Burns, A.G. and Killeen, T.L.}, title={ The equatorial neutral thermospheric response to geomagnetic (forcing) }, journal={Geophysical Research Letters}, volume={19}, number={10}, year={1992}, month={May}, pages={977-80}, abstract={ Thermospheric temperature and neutral density measurements from Dynamics Explorer 2 have been used to study the time-dependent response of the equatorial thermosphere to geomagnetic forcing. Data taken following the onsets of several different isolated geomagnetic storms have been used in a superposed-epoch scheme to investigate the characteristic response of the density and temperature structure of the equatorial thermosphere at approximately 350 km altitude in the morning and evening local-time sectors. The principal post-storm-onset features that have been observed are as follows: (1) Two travelling waves, one generated at northern high latitudes and one at southern high latitudes, pass through the equatorial thermosphere, with wave crests crossing the equator at a time lag of 3-6 hours after the storm onset. The maximum neutral density perturbations associated with these waves are approximately 15-25% for atomic oxygen and approximately 30-40% for molecular nitrogen. (2) Following the passage of these travelling waves, the densities and temperatures in the evening sector return relatively rapidly to their undisturbed state, whereas those in the morning sector have significant variations at longer lag times. In particular, significant increases in neutral density and temperature occur in the morning sector about 12 hours after the onset of the storm. The N/sub 2/ density enhancements are seen earliest in the summer hemisphere, while the O density enhancements are seen earliest in the winter hemisphere }, keywords={ atmospheric pressure and density atmospheric temperature magnetic storms thermosphere equatorial neutral thermospheric response temperature neutral density Dynamics Explorer 2 geomagnetic forcing geomagnetic storms travelling waves density perturbations evening sector morning sector 350 km N/sub 2/ O }, mynotes={UNREAD}, } @ARTICLE{ChenMar92, author={Chen, M.W. and Schulz, M. and Lyons, L.R. and Gorney, D.J.}, title={ Ion radial diffusion in an electrostatic impulse model for stormtime ring current formation }, journal={Geophysical Research Letters}, volume={19}, number={6}, year={1992}, month={Mar}, pages={621-4}, abstract={ Guiding-center simulations of stormtime transport of ring-current and radiation-belt ions having first adiabatic invariants mu >or approximately= 15 MeV/G (E>or approximately=165 keV at L approximately 3) are surprisingly well described (typically within a factor of or approximately= few days to few weeks) for both storms. Further analyses of observations of the sky brightness made with the lander cameras during the summer season are carried out to obtain improved estimates of other dust particle parameters. To understand the effect of dust content on atmospheric temperatures and winds, the derived radiative properties of the dust into a ID radiative convective model }, keywords={ convection cosmic dust Mars planetary atmospheres radiative transfer Martian atmosphere summer fall winter northern hemisphere global dust storms atmospheric temperatures winds atmosphere optical depth suspended dust particles autumn dust thermal radiative properties dust deposition Mars surface erosion one dimensional radiative convective model }, mynotes={UNREAD}, } @ARTICLE{EdmonsonFeb77, author={Edmonson, D.A. and Peterson, W.K. and Doering, J.P. and Feldman, P.D.}, title={ High resolution electron energy spectra in an active aurora at the onset of the magnetic storm of March 26, 1976 }, journal={Geophysical Research Letters}, volume={4}, number={2}, year={1977}, month={Feb}, pages={75-8}, abstract={ The spectrum of high energy precipitating auroral electrons (2-26 keV) was measured at altitudes from 97-175 km at the onset of the magnetic storm of 26 March 1976 by a rocket borne experiment launched from Ft. Churchill, Manitoba. The spectra show an unusual double-peaked distribution, with maxima at 4.5 and 17 keV, that persists for the full four minutes of data acquisition. Multiple structure within the main peaks is also noted. The energies and intensities of the two peaks observed at 163 km and 0 degrees pitch angle vary independently during a sudden brightening on the downleg of the rocket flight }, keywords={ atmospheric electron precipitation aurora magnetic storms active aurora high energy precipitating auroral electrons rocket borne experiment high resolution electron energy spectra 1976 March 26 magnetic storm onset 2 to 26 keV 97 to 175 km altitude }, mynotes={UNREAD}, } @ARTICLE{HoffmanNov75, author={Hoffman, R.A. and Maynard, N.C. and Smith, P.H. and Cahill, L.J. and Jr., Anderson and R.R., Fritz and T.A., Williams and D.J., Konradi and A. and Gurnett, D.A.}, title={ Explorer 45 (S/sup 3/-A) observations of the magnetosphere and magnetopause during the August 4-6, 1972, magnetic storm period }, journal={Journal of Geophysical Research}, volume={80}, number={31}, year={1975}, month={Nov}, pages={4287-96}, abstract={ The Explorer 45 (S/sup 3/-A) satellite performed extensive field and particle measurements in the heart of the magnetosphere during the double magnetic storm period of August 4-6, 1972. Both the ground level magnetic records and the magnetic field deformations measured along the orbit by the satellite indicated the existence of only a moderate ring current. This was confirmed by the measurements of the total proton energy density by the on-board particle detectors, which showed a maximum energy density less than the densities observed during the December 1971 and June 1972 magnetic storms. The plasmapause in the noon quadrant was eroded continuously from the onset of the first storm at the beginning of August 4 to an altitude below L=2.07 at about 1800 hours on August 5. Throughout the entire orbit during which the second sudden commencement occurred a large amount of low-frequency electric and magnetic field noise was encountered. The most remarkable observation during this orbit was the contraction of the magnetopause to distances inside the satellite location at L=5.2 }, keywords={ magnetic storms magnetosphere magnetosphere magnetopause magnetic storm period magnetic field deformations ring current magnetic field noise 1972 August 4 to 6 Explorer 45 satellite charged particle detection low frequency electric field noise }, mynotes={UNREAD}, } @ARTICLE{HayakawaJan75, author={Hayakawa, M. and Tanaka, Y. and Ohtsu, J.}, title={ Satellite and ground observations of magnetospheric VLF hiss associated with the severe magnetic storm on May 25-27, 1967 }, journal={Journal of Geophysical Research}, volume={80}, number={1}, year={1975}, month={Jan}, pages={86-92}, abstract={ The purpose of this paper is to make clear the characteristics of magnetospheric VLF hiss during storm times. The study is based on the VLF observations on board the Ariel 3 satellite as well as on the ground during the severe magnetic storm of May 25-27, 1967. Soon after the onset of the main phase there appeared the VLF hiss in the morning sector of the magnetosphere ('morning hiss') on the satellite as well as ground records, but the hiss is not observed in the evening sector. It was not until during the recovery phase that the stationary occurrence of strong VLF hiss could be recognized in the evening side of the magnetosphere ('evening hiss'). The important features of the morning and evening hiss are described and some discussions concerning their generation mechanism by the ring current particles are given }, keywords={ atmospherics magnetic storms magnetosphere 1967, May 25-27 atmospherics magnetospheric VLF hiss magnetic storm Ariel 3 }, mynotes={UNREAD}, } @ARTICLE{BasuAug74, title={ VHF ionospheric scintillations at L=2.8 and formation of stable auroral red arcs by magnetospheric heat conduction }, journal={Journal of Geophysical Research}, volume={79}, number={22}, year={1974}, month={Aug}, pages={3155-60}, abstract={ The 137-MHz amplitude scintillation data obtained from the ATS 3 satellite at a mid-latitude station (L=2.8) are utilized to study the temporal behavior of electron density irregularities following sudden commencements of intense magnetic storms. Comparison with the equatorial Dst index shows that the onset of scintillations is controlled by the universal time of commencement of the main and rapid recovery phases of storms. Total electron content data obtained simultaneously are used to show that the plasmapause-associated ionospheric trough moves to the vicinity of the observing point during the onsets of such universal time controlled scintillations. The magnetospheric heat conduction into the ionosphere during these storms, which sometimes causes stable auroral red arcs near the plasmapause, is found to produce field-aligned irregularities. A persistence of local time dominated scintillations following such storm time onsets is noted. The results of this study indicate that mid-latitude scintillations following large magnetic storms may have a storm time component in addition to the widely known local midnight component }, keywords={ aurora ionosphere ionospheric electromagnetic wave propagation magnetosphere radiowave propagation 137 MHz scintillation mid latitudes VHF ionospheric scintillations L stable auroral red arcs magnetospheric heat conduction ATS3 electron density irregularities sudden commencements intense magnetic storms equatorial Dst index plasmapause }, mynotes={UNREAD}, } @ARTICLE{DaviesFeb74, title={ Studies of ionospheric storms using a simple model }, journal={Journal of Geophysical Research}, volume={79}, number={4}, year={1974}, month={Feb}, pages={605-13}, abstract={ The ionospheric storm model is based on a heat source located at magnetic noon on Feldstein's auroral oval. The rotation of the Earth produces an apparent motion of the source that is greater than the speed of the disturbance. This gives rise to a wake or front that sweeps over the globe and determines the onset time of the negative phase, which results from a change in chemical composition. At the front focusing will occur, which accounts for the sudden drop in electron density (or content) sometimes observed. Calculated diurnal variations of maximum electron density and height are in general agreement with the positive and negative phases of storms }, keywords={ Earth rotation ionosphere storms ionospheric storm model heat source magnetic noon auroral oval rotation onset time negative phase chemical composition electron density }, mynotes={UNREAD}, } @ARTICLE{GulbrandsenAug73, title={ Relation between coronal lambda 5303 intensity, recurrent geomagnetic storms, and solar sector structure }, journal={Journal of Geophysical Research}, volume={78}, number={22}, year={1973}, month={Aug}, pages={4787-91}, abstract={ A correlation is demonstrated between recurrent geomagnetic storms and longitudinal zones of low coronal lambda 5303 intensity, called L zones. The onset of a storm occurs about 2 days after the central meridian passage of an L zone. The L zones partly coincide with regions of low brightness temperature at the 9.1-cm microwave emission. Comparison with data of the interplanetary sector structure suggests that an L zone is located to the east of a solar magnetic sector boundary }, keywords={ interplanetary magnetic fields magnetic storms solar activity solar corona solar magnetism solar radiation coronal 5303 Angstroms intensity recurrent geomagnetic storms solar sector structure longitudinal zones central meridian passage low brightness temperature interplanetary sector structure }, mynotes={UNREAD}, } @ARTICLE{BurnsJan72, author={Burns, A.L. and Krimigis, S.M.}, title={ Changes in the distribution of low-energy trapped protons associated with the April 17, 1965, magnetic storm }, journal={Journal of Geophysical Research}, volume={77}, number={1}, year={1972}, month={Jan}, pages={112-30}, abstract={ The absolute intensity of geomagnetically trapped protons in the energy ranges 0.52or approximately=2.5 and all sampled mod B mod ranges, which persisted for at least 36 days after the storm. The effect of the sudden commencement was a general depression in the intensities and a hardening of the energy spectrums, although the intensities recovered to their prestorm level during the initial phase. The major redistribution was apparently initiated by the polar substorm that began at approximately 0620 UT on April 18 and continued long after (to 1100 UT) the substorm had subsided ( approximately 0800 UT). During the recovery phase, a secondary peak developed in the intensity profile at L approximately 3.5 for 0.52-Mev protons that had no counterpart at this energy at the equator (L.R. Davis, private communication, 1971). No such peak was observed for 0.9-Mev protons. The over-all effect of the storm on the steady-state distribution was a nonadiabatic one with an increase in intensities at L0.94 Mev coincident with the onset of the magnetic storm of May 25, and the subsequent growth of the peak flux at L approximately=3.0 (pre-storm L approximately=3.8). Over the region 2.5600 km/s. Ion velocity-space distributions confirm that the flows are indeed convective flows of a single-ion population and not counterstreaming beams, as is often the case at the plasma sheet boundary. The fast tailward flows observed at the initial stage of reconnection were localized to a thin layer surrounding the neutral sheet. The magnitude of the current disruption and the region I sense field-aligned currents associated with reconnection were sufficiently large to explain the intensity of the substorm current wedge, as inferred from ground magnetometers }, keywords={ atmospheric electricity atmospheric movements magnetic storms magnetosphere magnetotail reconnection onset small substorm April 15 1979 current sheet plasma sheet acceleration X-type neutral line earthward bursty bulk flows ion velocity-space distributions convective flows single-ion population plasma sheet boundary tailward flows reconnection current disruption region I sense field-aligned currents substorm current wedge AD 1979 04 15 600 km/s 30 km/s }, mynotes={UNREAD}, } @ARTICLE{FedderOct95, author={Fedder, J.A. and Slinker, S.P. and Lyon, J.G. and Elphinstone, R.D.}, title={ Global numerical simulation of the growth phase and the expansion onset for a substorm observed by Viking }, journal={Journal of Geophysical Research}, volume={100}, number={A10}, year={1995}, month={Oct}, pages={19083-93}, abstract={ Reports the first global magnetohydrodynamic (MHD) simulation of an actual magnetospheric substorm, which was recorded by the Viking spacecraft on October 19, 1986. The simulation is driven by IMP 8 solar wind parameters measured upstream of the Earth's bow shock. The substorm, which had expansion onset at 1132 UT, was caused by a brief period of southward interplanetary magnetic field (IMF) and two weak solar wind shocks. The simulation model includes a self-consistent auroral ionospheric conductance depending directly on the MHD magnetospheric plasma parameters and magnetic field. Synthetic auroral emissions, derived from simulation results, are compared to the Viking images, which show considerable dayside activity preceding the substorm. The authors also compare model-derived synthetic AU and AL indices to geomagnetic measurements. The simulation results are seen to be in reasonable agreement with the observations throughout the growth phase and expansion onset. Moreover, the results allow one to form conclusions concerning which essential processes were responsible for the substorm occurrence. These results are a highly encouraging first step leading toward development of a space weather forecasting methodology based on the directly measured solar input }, keywords={ aurora magnetic storms plasma magnetohydrodynamics gobal numerical simulation growth phase expansion onset substorm magnetohydrodynamic simulation solar wind parameters southward interplanetary magnetic field solar wind shocks self-consistent auroral ionospheric conductance magnetic field auroral emissions dayside activity AU indices AL indices space weather forecasting methodolog AD 1986 10 19 }, mynotes={UNREAD}, } @ARTICLE{ElphinstoneMay95, author={Elphinstone, R.D. and Hearn, D.J. and Cogger, L.L. and Murphree, J.S. and Singer, H. and Sergeev, V. and Mursula, K. and Klumpar, D.M. and Reeves, G.D. and Johnson, M. and Ohtani, S. and Potemra, T.A. and Sandahl, I. and Nielsen, E. and Persson, M. and Opgenoorth, H. and Newell, P.T. and Feldstein, Y.I.}, title={ Observations in the vicinity of substorm onset: implications for the substorm process }, journal={Journal of Geophysical Research}, volume={100}, number={A5}, year={1995}, month={May}, pages={7937-69}, abstract={ Multi-instrument data sets from the ground and satellites at both low and high altitude have provided new results concerning substorm onset and its source region in the magnetosphere. Twenty-six out of 37 substorm onset events showed evidence of azimuthally spaced auroral forms (AAFs) prior to the explosive poleward motion associated with optical substorm onset. The azimuthal wavelengths associated with these onsets were found to range between 132 and 583 km with a mean value of 307+or-115 km. The occurrence rate increased with decreasing wavelength down to a cutoff wavelength near 130 km. AAFs can span 8 hours of local time prior to onset and generally propagate eastward in the morning sector. Onset itself is, however, more localized spanning only about 1 hour local rime. The average location of the peak intensity for 80 onsets was 65.9+or-3.5 CGMlat, 22.9+or-1.2 Mlt, whereas the average location of the AAF onsets was at 63.8+or-3.3 CGMlat, 22.9+or-1.1 Mlt. AAF onsets occur during time periods when the solar wind pressure is relatively high. These low-latitude wavelike onsets appear as precursors in the form of long-period magnetic pulsations (Pc 5 band) and frequently occur on the equatorward portion of the double oval distribution. AAFs brighten in conjunction with substorm onset leading to the conclusion that they are a growth phase activity causally related to substorm onset. Precursor activity associated with these AAFs is also seen near geosynchronous orbit altitude and examples show the relationship between the various instrumental definitions of substorm onset. The implied mode number (30 to 135) derived from this work is inconsistent with cavity mode resonances but is consistent with a modified flute/ballooning instability which requires azimuthal pressure gradients. It is suggested that this instability exists in growth phase but that an additional factor exists in the premidnight sector which results in an explosive onset. The extended source region and }, keywords={ magnetic storms magnetosphere magnetic storm substorm onset azimuthally spaced auroral form AAF explosive poleward motion long-period magnetic pulsation Pc 5 precursor activity multiple onset morphology }, mynotes={UNREAD}, } @ARTICLE{NakaiMar95, author={Nakai, H. and Kamide, Y.}, title={ Magnetic field changes at the neutral sheet associated with substorm expansion onset: a model prediction and observations }, journal={Journal of Geophysical Research}, volume={100}, number={A3}, year={1995}, month={Mar}, pages={3521-30}, abstract={ Using a simple numerical model of the magnetotail current system, substorm-associated changes in the large-scale distribution of the neutral sheet current and the corresponding magnetic field at the neutral sheet are examined. In the current model it is assumed that the radial gradient of the neutral sheet current at the late expansion phase of substorms is steeper than that just prior to the expansion onset. It is shown that the current model can successfully reproduce the observed characteristics of the so-called magnetic field dipolarization in the near-Earth magnetotail. Comparing various satellite observations with what the current model predicts, the location of the substorm initiation and the propagation of the magnetic field dipolarization are discussed. There are at least three distinct types of the radial distribution of the neutral sheet current, depending on magnetospheric conditions: quiet times, just prior to substorm expansion onset, and near the end of the expansion phase (or the beginning of the recovery phase) of substorms }, keywords={ magnetic fields magnetic storms magnetosphere magnetic field changes magnetosphere substorm expansion onset numerical model prediction large-scale distribution neutral sheet current substorm-associated changes magnetotail current system radial gradient late expansion phase magnetic field dipolarization near-Earth magnetotail satellite observations substorm initiation magnetospheric conditions quiet times recovery phase }, mynotes={UNREAD}, } @ARTICLE{PerssonAug94, author={Persson, M.A.L. and Opgenoorth, H.J. and Pulkkinen, T.I. and Eriksson, A.I. and Dovner, P.O. and Reeves, G.D. and Belian, R.D. and Andre, M. and Blomberg, L.G. and Erlandson, R.E. and Boehm, M.H. and Aikio, A.T. and Haggstrom, I.}, title={ Near-Earth substorm onset: a coordinated study }, journal={Geophysical Research Letters}, volume={21}, number={17}, year={1994}, month={Aug}, pages={1875-8}, abstract={ Presents simultaneous satellite and ground-based measurements of a substorm. Throughout the initial substorm expansion, southward drifting arcs are observed poleward of the expanding substorm aurora, indicating two independent systems of particle precipitation. Freja passes the brightening onset arc in the topside ionosphere near the moment of the substorm onset, observing an Alfven wave, field aligned current and oxygen ion outflow. The substorm onset occurs at low magnetospheric L-shells, near the poleward edge of the region of trapped particles. The location and time for the substorm injection are confirmed by geostationary spacecraft together with magnetometers, all-sky cameras and radar on the ground. The authors believe that the substorm onset may be triggered by modification of the oxygen content of the inner magnetosphere during the growth-phase caused by ionospheric ion outflow }, keywords={ atmospheric elementary particle precipitation aurora ionospheric disturbances magnetic storms near-Earth substorm onset southward drifting arcs expanding substorm aurora particle precipitation Freja data brightening onset topside ionosphere Alfven wave field aligned current O ion outflow low magnetospheric L-shells trapped particles substorm injection growth-phase ionospheric ion outflow AD 1993 03 02 O }, mynotes={UNREAD}, } @ARTICLE{NakamuraJan94, author={Nakamura, R. and Baker, D.N. and Yamamoto, T. and Belian, R.D. and Bering, E.A. and III, Benbrook and J.R. and Theall, J.R.}, title={ Particle and field signatures during pseudobreakup and major expansion onset }, journal={Journal of Geophysical Research}, volume={99}, number={A1}, year={1994}, month={Jan}, pages={207-21}, abstract={ The temporal and spatial scales of the onset of two types of substorm events are investigated. These substorms were cases where the expansion onset had precursor localized auroral activation without significant negative bay enhancement, that is, "pseudobreakup". High-resolution energetic particle and magnetic field data at synchronous orbit are used for the analysis together with auroral and magnetic field data simultaneously taken from ground-based instrumentation. The auroral structure following the pseudobreakup significantly resembled the major expansion aurora, except in its spatial scale. Typical magnetospheric onset signatures such as tail current diversion, dipolarization, and injection were observed associated with some of the pseudobreakups. The major expansion, on the other hand, consisted of a number of rather localized injections and expansions, each of which had timescales of 2-8 min, a comparable timescale to that of pseudobreakups. This study shows that there does not appear to be any phenomenological differences between pseudobreakups and major expansion onsets. The major difference between pseudobreakups and major expansion onsets would be the number of occurrences, as well as the intensity and the scale size of the magnetospheric source }, keywords={ magnetic storms magnetosphere magnetic storm field signature pseudobreakup breakup major expansion onset spatial scale substorm precursor localized auroral activation negative bay enhancement particle signature auroral structure aurora tail current diversion dipolarization }, mynotes={UNREAD}, } @ARTICLE{OhtaniNov93, author={Ohtani, S. and Anderson, B.J. and Sibeck, D.G. and Newell, P.T. and Zanetti, L.J. and Potemra, T.A. and Takahashi, K. and Lopez, R.E. and Angelopoulos, V. and Nakamura, R. and Klumpar, D.M. and Russell, C.T.}, title={ A multisatellite study of a pseudo-substorm onset in the near-Earth magnetotail }, journal={Journal of Geophysical Research}, volume={98}, number={A11}, year={1993}, month={Nov}, pages={19355-67}, abstract={ The paper reports multisatellite and ground observations of two pseudo-substorm onset events that occurred successively at 0747 UT and 0811 UT, May 30, 1985, paying more attention to the 0747 UT onset. The distinguishing features of the 0747 UT event are as follows. (1) The substorm-associated tail reconfiguration started in a very localized region in the near-Earth magnetotail. (2) The magnitude of the current disruption decreased markedly as the disruption region expanded tailward. (3) On the ground the onset of a very small negative bay ( approximately 40 nT) was observed simultaneously with the onset of the current disruption, but over a much wider local time sector than the near-Earth tail reconfiguration. Positive bay onsets at mid-latitudes also had a longitudinally wide distribution. From these features the authors infer that in the present event the current disruption took place filamentarily near AMPTE/CCE at approximately 8.8 R/sub E/. It is also inferred that pseudo-substorm onsets are distinguished from standard substorm onsets by the absence of a global expansion of the current disruption, and that the spatial scale of the onset region in the magnetosphere is not a major difference between the two. The present study suggests that the spatial distribution of the magnetic distortion before onsets is an important factor to determine the expansion scale of the current disruption. It is also suggested that the current disruption is basically an internal process of the magnetosphere }, keywords={ atmospheric electricity magnetic storms magnetosphere multisatellite study pseudosubstorm onset near-Earth magnetotail May 30 1985 substorm current disruption negative bay global expansion magnetosphere spatial distribution magnetic distortion AD 1985 05 30 8.8 Earthradii }, mynotes={UNREAD}, } @ARTICLE{LyonsNov92, author={Lyons, L.R. and Samson, J.C.}, title={ Formation of the stable auroral arc that intensifies at substorm onset }, journal={Geophysical Research Letters}, volume={19}, number={21}, year={1992}, month={Nov}, pages={2171-4}, abstract={ A companion paper, Samson et al. (1992b), presents observational evidence that the stable, growth-phase auroral arc that intensifies at substorm expansion phase onset often forms on magnetic field lines that map to within approximately 1 to 2 R/sub e/ of synchronous. The equatorial plasma pressure is 1 to 10 nPa in this region, which can give a cross-tail current >0.1 A/m. In this paper, the authors propose that the arc is formed by a perpendicular magnetospheric-current divergence that results from a strong dawn-to-dusk directed pressure gradient in the vicinity of magnetic midnight. They estimate that the current divergence is sufficiently strong that a >1 kV field-aligned potential drop is required to maintain ionospheric-current continuity. It is suggested that the azimuthal pressure gradient results from proton drifts in the vicinity of synchronous orbit that are directed nearly parallel to the cross-tail electric field }, keywords={ aurora ionosphere magnetosphere aurora intensification formation magnetosphere ionosphere stable auroral arc substorm onset growth-phase auroral arc expansion phase onset perpendicular magnetospheric-current divergence dawn-to-dusk pressure gradient magnetic midnight field-aligned potential drop }, mynotes={UNREAD}, } @ARTICLE{LyonsSep92, author={Lyons, L.R. and Huang, C.Y.}, title={ Observations of plasma sheet expansion at substorm onset, R=15 to 22 R/sub e/ }, journal={Geophysical Research Letters}, volume={19}, number={18}, year={1992}, month={Sep}, pages={1807-10}, abstract={ The authors have used a large number of auroral magnetograms to identify four isolated substorms and estimate their onset times. At the onsets, ISEE-1 was in the vicinity of magnetic midnight at radial distances of 15.6 to 21.8 R/sub e/ and very near the outer boundary of the plasma sheet. The authors find that, for each event, the plasma sheet expanded, and the magnetic field dipolarized at the inferred onset time. Their most definitive event occurred while ISEE was at a geocentric radial distance of 21.8 R/sub e/. This result conflicts with previous understanding, though further verification of the result is required. Their observations show very similar characteristics to those observed at synchronous orbit, and they are consistent with an extension of a portion of the substorm current wedge to the radial distance of the satellite. If this explanation is correct, ISEE must have been within the longitude range of the substorm current wedge at the onsets }, keywords={ magnetic storms magnetosphere magnetic field depolarization magnetosphere plasma sheet expansion substorm onset auroral magnetograms ISEE-1 substorm current wedge 15.6 to 21.8 Earthradii }, mynotes={UNREAD}, } @ARTICLE{OhtaniMar92, author={Ohtani, S. and Kokubun, S. and Russell, C.T.}, title={ Radial expansion of the tail current disruption during substorms: a new approach to the substorm onset region }, journal={Journal of Geophysical Research}, volume={97}, number={A3}, year={1992}, month={Mar}, pages={3129-36}, abstract={ The substorm onset region and the radial development of the tail current disruption are examined from a new viewpoint. The reconfiguration of the magnetotail field at substorm onset can be understood in terms of a sudden decrease (disruption) in tail current intensity. The north-south component (B/sub Z/) is very sensitive to whether the spacecraft position is earthward or tailward of the disruption region, while the change in the Sun-Earth component (B/sub X/) is most sensitive to the change in tail current intensity near the spacecraft. If the current disruption starts in a localized range of radial distance and expands radially, a distinctive phase relationship between the changes in B/sub X/ and B/sub Z/ is expected to be observed. This phase relationship depends on whether the current disruption starts on the earthward side or the tailward side of the spacecraft. Thus it is possible to infer the direction of the radial expansion of the current disruption from magnetic field data of a single spacecraft }, keywords={ magnetic storms magnetosphere magnetosphere magnetotail radial expansion electric current disruption magnetic storm AD 1979 03 06 tail current disruption substorm onset region sudden decrease }, mynotes={UNREAD}, } @ARTICLE{LewisAug91, title={ On the apparent randomness of substorm onset }, journal={Geophysical Research Letters}, volume={18}, number={8}, year={1991}, month={Aug}, pages={1627-30}, abstract={ The onset of the expansion phase of substorms is currently unpredictable, that unpredictability being related to the nonlinear nature of the solar wind-magnetosphere interaction. Using the mathematics of catastrophe theory it is possible to describe the substorm phenomenon in terms of a fundamental singularity of the solar wind-magnetosphere interaction. The apparently random nature of substorm onset can then be explained as the result of an unfolding of the singularity of the cusp catastrophe which is in principle predictable. Substorm expansions are triggered when two features of the solar wind-magnetosphere interaction are critically functionally related }, keywords={ magnetic storms magnetic storm random onset apparent randomness substorm onset expansion phase catastrophe theory solar wind-magnetosphere interaction unfolding singularity cusp catastrophe }, mynotes={UNREAD}, } @ARTICLE{KanJan91, title={ Dipolarization: a consequence of substorm expansion onset }, journal={Geophysical Research Letters}, volume={18}, number={1}, year={1991}, month={Jan}, pages={57-60}, abstract={ Dipolarization observed in the near-Earth plasma sheet can be initiated by the substorm expansion onset. Field-aligned currents at the substorm expansion onset are enhanced first in the ionosphere in response to an enhanced magnetospheric convection. Closure of substorm field-aligned currents through the plasma sheet can disrupt the cross-tail current to cause dipolarization in the plasma sheet. The electric field induced by the current disruption can launch a fast-mode compression wave to result in the plasma injection event. A new X line can form tailward of the dipolarization region during the substorm expansion phase. A timing sequence of substorm events is inferred from the proposed conceptual model of substorms based on the magnetosphere-ionosphere coupling process on the Alfven bounce time scale }, keywords={ magnetic storms magnetosphere dipolarization magnetosphere magnetic storm dipole substorm expansion onset near-Earth plasma sheet }, mynotes={UNREAD}, } @ARTICLE{WilliamsApr90, author={Williams, D.J. and Mitchell, D.G. and Huang, C.Y. and Frank, L.A. and Russell, C.T.}, title={ Particle acceleration during substorm growth and onset }, journal={Geophysical Research Letters}, volume={17}, number={5}, year={1990}, month={Apr}, pages={587-90}, abstract={ Presents ISEE-1 observations of ion and electron energization made at approximately 11 R/sub E/ during a substorm event occurring on 2 April 1978. An analysis of the dominant cross-tail current systems in this event (Mitchell et al., 1990) has allowed the authors to uniquely associate particle energization processes with the development and/or disruption of the cross-tail currents. They find that significant ion acceleration occurs as the ions participate in serpentine cross-tail motion (Speiser, 1965), establishing the dominant plasma sheet current system just prior to onset. As this current disrupts, the magnetic field configuration dipolarizes and further ion energization and the bulk of the electron energization occurs. During dipolarization energization is due primarily to the inductive electric field, including betatron and Fermi acceleration processes }, keywords={ magnetic storms magnetosphere trapped particle acceleration ion acceleration magnetosphere magnetotail AD 1978 04 02 substorm growth onset electron energization disruption cross-tail currents ion acceleration serpentine cross-tail motion }, mynotes={UNREAD}, } @ARTICLE{KanJun88, author={Kan, J.R. and Zhu, L. and Akasofu, S.-I.}, title={ A theory of substorms: onset and subsidence }, journal={Journal of Geophysical Research}, volume={93}, number={A6}, year={1988}, month={Jun}, pages={5624-40}, abstract={ It is shown by a computer simulation study of the magnetosphere-ionosphere (M-I) coupling that an enhanced magnetospheric convection can lead to auroral substorm onset in about 40 min after a southward turning of the IMF. The simulation results show that the enhanced M-I coupling can produce intense upward field-aligned currents in the midnight sector near the poleward boundary of a high-conductance belt associated with the diffuse auroral precipitation. Two necessary conditions for substorm onset are that: (1) the polar cap potential must exceed a certain value (about 70 kV in our model), and (2) the convection reversal region must overlap with the poleward gradient of the diffuse auroral conductance in the ionosphere in the midnight sector. The matching ensures that the divergence of the Pedersen current collocates with the divergence of the Hall current to maximize the upward field-aligned current near the poleward boundary of the diffuse aurora in the midnight sector for substorm onset. Without the matching, the auroral brightening would not occur. Substorms subside when one of the two necessary conditions is no longer satisfied }, keywords={ atmospheric electricity aurora ionosphere magnetic storms magnetosphere plasma magnetosphere ionosphere coupling atmosphere magnetic storm substorms onset subsidence computer simulation convection upward field-aligned currents midnight sector high-conductance belt diffuse auroral precipitation polar cap potential reversal region divergence Pedersen current Hall current diffuse aurora }, mynotes={UNREAD}, } @ARTICLE{de-Groot-HedlinJun87, author={de Groot-Hedlin, C.D. and Rostoker, G.}, title={ Magnetic signatures of precursors to substorm expansive phase onset }, journal={Journal of Geophysical Research}, volume={92}, number={A6}, year={1987}, month={Jun}, pages={5845-56}, abstract={ The expansive phase of magnetospheric substorms involves the development of auroral loops and surges with particular emphasis on the westward travelling surge which is identified with the western edge of the substorm current wedge. The authors use as a working hypothesis the contention that the wavelike auroral structures associated with the current wedge are a manifestation of the action of Kelvin-Helmholtz instability at the interface between the central plasma sheet (CPS) and the adjacent boundary layer plasmas in the deep magnetotail. Based on this concept, the authors used ground-based magnetometer data in an attempt to identify the growth of ionospheric current systems which might be associated with the growth of the Kelvin-Helmholtz instability. The authors found that the expansive phase is preceded by the growth of a weak substorm current wedge which strengthens explosively at the time of onset. The authors suggest that field-aligned current flows out of the ionosphere as part of a process damping a growing wave at the CPS/boundary layer interface }, keywords={ magnetic fields magnetic storms magnetosphere magnetic signatures precursors substorm expansive phase onset magnetospheric substorms auroral loops surges westward travelling surge wavelike auroral structures Kelvin-Helmholtz instability central plasma sheet boundary layer plasmas magnetotail ground-based magnetometer data ionospheric current systems current wedge field-aligned current flows }, mynotes={UNREAD}, } @ARTICLE{EsareyApr87, author={Esarey, E. and Molvig, K.}, title={ A turbulent mechanism for substorm onset in the Earth's magnetotail }, journal={Geophysical Research Letters}, volume={14}, number={4}, year={1987}, month={Apr}, pages={367-70}, abstract={ Turbulence within the plasma sheet of the magnetotail is shown to destabilize the tearing mode even for cases where the equilibrium magnetic field has a normal component within the sheet. In the absence of turbulence, a finite normal magnetic field suppresses the electron wave-particle resonance and stabilizes the tearing mode. Turbulence leads to spatial diffusion of the electron orbits, thus allowing for resonance between the electrons and the tearing perturbation. This provides the dissipation necessary for instability and hence, magnetic field line reconnection. Furthermore, by accounting for the finite extent of the tearing perturbation in the cross-tail direction, the existence of a threshold for instability is derived. This threshold predicts instability for sufficiently small values of the normal magnetic field. Hence, substorm onset proceeds when the turbulent plasma sheet becomes sufficiently elongated }, keywords={ magnetic storms magnetosphere magnetic storm plasma instability turbulent mechanism substorm onset magnetotail plasma sheet destabilize tearing mode turbulence spatial diffusion electron orbits dissipation magnetic field line reconnection }, mynotes={UNREAD}, } @ARTICLE{SmitsJan86, author={Smits, D.P. and Hughes, W.J. and Cattell, C.A. and Russell, C.T.}, title={ Observations of field-aligned currents, waves, and electric fields at substorm onset }, journal={Journal of Geophysical Research}, volume={91}, number={A1}, year={1986}, month={Jan}, pages={121-34}, abstract={ Substorm onsets, identified by Pi 2 pulsations, are studied using magnetometer and electric field data from ISEE 1 and magnetometer data from the geosynchronous satellites GOES 2 and 3. The mid-latitude magnetometer data provide the means of both timing and locating the substorm onset so that the spacecraft locations with respect to the substorm current systems are known. During two intervals, each containing several onsets or intensifications, ISEE 1 observed field-aligned current signatures beginning simultaneously with the mid-latitude Pi 2 pulsation. Close to the Earth broadband bursts of wave noise were observed in the electric field data whenever field-aligned currents were detected. Plasma data confirm that the plasma sheet thinned and subsequently expanded at onset. Electric field data show that the plasma moved in the opposite direction to the plasma sheet boundary as the boundary expanded. The plasma motion was towards the center of the plasma sheet and Earthwards }, keywords={ atmospheric electricity atmospherics magnetic storms magnetosphere micropulsations plasma magnetosphere magnetic storm onset phase GOES 3 atmospheric electricity ULF atmospherics AD 1980 04 15 micropulsations electrostatic waves AD 1979 07 01 plasma sheet thinning plasma sheet expansion plasma Earthward flow Earth radii 006.6 westward auroral electrojets field-aligned currents electric fields substorm onset Pi 2 pulsations electric field data ISEE 1 geosynchronous satellites GOES 2 mid-latitude magnetometer data spacecraft locations substorm current systems broadband bursts wave noise plasma sheet boundary plasma motion }, mynotes={UNREAD}, } @ARTICLE{SauvaudMay84, author={Sauvaud, J.A. and Saint-Marc, A. and Dandouras, J. and Reme, H. and Korth, A. and Kremser, G. and Parks, G.K.}, title={ A multisatellite study of the plasma sheet dynamics at substorm onset }, journal={Geophysical Research Letters}, volume={11}, number={5}, year={1984}, month={May}, pages={500-3}, abstract={ A multi-satellite study has been conducted on the temporal relationship between energetic particle injections observed at the geostationary orbit onboard GEOS-2 and decreases of thermal plasma sheet particle fluxes ('plasma sheet thinnings') observed in the more distant geomagnetic tail onboard the ISEE-1 and -2 spacecraft. A case by case analysis as well as a statistical study of 100 events recorded from February to May 1979 and 1980 show that particle injection and particle flux decrease are detected to within less than 5 minutes of each other, for an average intersatellite distance of 15.7 R/sub E/. The observed spread in Delta t corresponds best to Alfven wave transit times. These particle phenomena are observed at the onset of the auroral zone magnetic bays. The results reported suggest that the dynamics of the inner and outer boundaries of the plasma sheet are closely related to each other and controlled by large scale processes that develop at substorm onset inside the magnetospheric tail and result in a cross-tail current disruption }, keywords={ magnetic storms magnetosphere ISEE-2 multisatellite study plasma sheet dynamics substorm onset energetic particle injections GEOS-2 particle fluxes geomagnetic tail ISEE-1 February to May 1979 Alfven wave auroral zone magnetic bays magnetospheric tail cross-tail current disruption }, mynotes={UNREAD}, } @ARTICLE{NishidaSep83, author={Nishida, A. and Kamide, Y.}, title={ Magnetospheric processes preceding the onset of an isolated substorm: a case study of the March 31, 1978, substorm }, journal={Journal of Geophysical Research}, volume={88}, number={A9}, year={1983}, month={Sep}, pages={7005-14}, abstract={ Examines in detail the effect of a southward turning of the interplanetary magnetic field (IMF) on the state of the magnetosphere, taking advantage of the availability of the data from IMS magnetometer meridian chains and from several spacecraft. A clear onset substorm occurred on March 31, 1978, when the magnetometer stations were located in the midnight to morning sector and the spacecraft were near the equatorial plane of the nightside magnetosphere. The onset time of the substorm expansion phase could be determined unambiguously in terms of both ground-based magnetic and auroral signatures, and there was an interval lasting about 1 hour between the IMF southward turning and this onset. In this intervening interval the ionospheric current system of the DP 2 type developed }, keywords={ interplanetary magnetic fields magnetic storms solar wind magnetic storm AD 1978 03 31 IMF polarity change electric current solar wind preceding onset isolated substorm southward turning interplanetary magnetic field magnetosphere expansion phase ionospheric current }, mynotes={UNREAD}, } @ARTICLE{NagaiSep83, author={Nagai, T. and Baker, D.N. and Higbie, P.R.}, title={ Development of substorm activity in multiple-onset substorms at synchronous orbit }, journal={Journal of Geophysical Research}, volume={88}, number={A9}, year={1983}, month={Sep}, pages={6994-7004}, abstract={ The development of substorm activity at synchronous orbit (6.6 R/sub E/) for multiple-onset substorms was studied by using the energetic particle and magnetic field data in three local time groups (the afternoon region, the premidnight region, and the postmidnight region). The geostationary spacecraft 1976-059 and 1977-007 provided the measurements of 30- to 2000-keV electrons and 145- to 560-keV protons, GMS the measurements of >2000 keV electrons, and GOES 1 and GOES 2 the measurements of the magnetic field. The ground magnetic variations in a wide area were examined to determine the general characteristics of substorm activity and the timing of various phenomena. The substorm evolutions showed a variety of forms at synchronous orbit }, keywords={ magnetic storms magnetosphere magnetic storm substorm activity multiple-onset development }, mynotes={UNREAD}, } @ARTICLE{AggsonMay83, author={Aggson, T.L. and Heppner, J.P. and Maynard, N.C.}, title={ Observations of large magnetospheric electric fields during the onset phase of a substorm }, journal={Journal of Geophysical Research}, volume={88}, number={A5}, year={1983}, month={May}, pages={3981-90}, abstract={ A large impulsive westward electric field was observed in the mid-night, low latitude, dipole L=7.5 region of the magnetospheric tail at the onset of a large substorm. The measurements were made with the electric field probes carried by ISEE 1. The electric field impulse was coincident with a sharp 60 nT steplike change in the x component of the magnetic field at the satellite and the onset of a sharp 60 nT decrease in the H component of the field at a magnetic observatory near the subconjugate point. The 2-min envelope of the westward E/sub y/ field correlates with the time derivative delta B/sub x// delta t of the collapsing magnetic field attributed to the decrease in the cross-tail current. Associated with this inductive impulse, large electric field variations are also observed on time scales of tens of seconds to tens of milliseconds. The low-frequency (10 s) wave variations show a coherent phase relationship between the electric and magnetic field that changes from correlative to anti-correlative during the event. These large time-dependent electric fields seem to have the proper amplitude, duration, and timing relative to the auroral substorm sequence to explain the energetic proton enhancements frequently observed near midnight both at synchronous orbit and in the magnetotail at times of substorm onsets }, keywords={ magnetic storms magnetosphere magnetic storm magnetosphere night magnetotail magnetic tail AD 1978 04 19 large onset phase substorm impulsive electric field low latitude inductive }, mynotes={UNREAD}, } @ARTICLE{ImhofOct82, author={Imhof, W.L. and Stadsnes, J. and Reagan, J.B. and Kilner, J.R. and Gaines, E.E. and Datlowe, D.W. and Mobilia, J. and Nakano, G.H.}, title={ Satellite bremsstrahlung X-ray measurements at the onset of a magnetospheric substorm }, journal={Journal of Geophysical Research}, volume={87}, number={A10}, year={1982}, month={Oct}, pages={8149-56}, abstract={ Bremsstrahlung X-ray (>21 keV) mappings and direct electron (>68 keV) measurements from the low-altitude polar-orbiting satellite P78-1 were performed at critical times and locations near the onset of a magnetospheric substorm on July 3, 1979 at approximately 2149 UT. The bremsstrahlung X-ray intensities emitted from the atmosphere over a wide range of longitudes and L shells were negligible just before the substorm onset, then rose to a maximum within about a minute or less, and remained at an enhanced level for the next nine minutes. The simultaneous X-ray measurements from the SBARMO-79 balloons and the P78-1 satellite indicate that the electron precipitation started at L=5-5.5 without a significant precipitation from higher L shells. A relatively sharp longitude decrease was observed in electron precipitation at positions east of approximately 30 degrees E or at magnetic local times after approximately 1.5 hours }, keywords={ atmospheric electron precipitation magnetic storms X-rays magnetosphere magnetic storm AD 1979 07 03 electron precipitation bremsstrahlung onset substorm atmosphere electron precipitation }, mynotes={UNREAD}, } @ARTICLE{KremserJun82, author={Kremser, G. and Bjordal, J. and Block, L.P. and Bronstad, K. and Havag, M. and Iversen, I.B. and Kangas, J. and Korth, A. and Madsen, M.M. and Niskanen, J. and Riedler, W. and Stadsnes, J. and Tanskanen, P. and Torkar, K.M. and Ullaland, S.L.}, title={ Coordinated balloon-satellite observations of energetic particles at the onset of a magnetospheric substorm }, journal={Journal of Geophysical Research}, volume={87}, number={A6}, year={1982}, month={Jun}, pages={4445-53}, abstract={ Coordinated observations of electron precipitation via X-ray measurements from three simultaneously flown balloons, and of energetic particles at the geosynchronous satellite GEOS 2, were used to investigate variations of the distribution of energetic charged particles at the onset of a magnetospheric substorm on July 3, 1979. It is concluded that the electron precipitation was directly related to the injection of electrons and that the injection took place well earthward of the near-Earth reconnection region postulated in some substorm models. A possible mechanism that would connect injection to reconnection is proposed. The influence of parallel electric fields on the particle distribution is discussed }, keywords={ atmospheric electron precipitation magnetic storms magnetosphere trapped particle magnetosphere magnetic storm AD 1979 07 03 energetic particles onset substorm electron precipitation variations injection reconnection }, mynotes={UNREAD}, } @ARTICLE{HonesMar82, author={Hones, E.W. and JR., Birn and J., Bame and S.J., Paschmann and G. and Russell, C.T.}, title={ On the three-dimensional magnetic structure of the plasmoid created in the magnetotail at substorm onset }, journal={Geophysical Research Letters}, volume={9}, number={3}, year={1982}, month={Mar}, pages={203-6}, abstract={ Reconnection of magnetic field lines at a neutral line that forms in the near-Earth region of the plasma sheet at substorm onset creates, from some longitudinal sector of the plasma sheet, a plasmoid that is then free to flow out of the magnetotail into the magnetosphere's wake. The magnetic field in the departing plasmoid frequently displays a strong positive or negative Y/sub SM/ component that has been difficult to reconcile with the reconnection geometry as it is traditionally depicted in two dimensions. The authors show that this deviation of the magnetic field is a manifestation of a draping of the newly reconnected field line loops toward the tail's central (midnight) meridian and that the draping is a consequence of the three-dimensional plasma flow associated with the reconnection process }, keywords={ magnetic storms magnetosphere magnetosphere magnetic storm disconnected three-dimensional magnetic structure plasmoid magnetotail substorm onset plasma sheet wake reconnected field line draping }, mynotes={UNREAD}, } @ARTICLE{KawasakiDec79, author={Kawasaki, K. and Rostoker, G.}, title={ Auroral motions and magnetic variations associated with the onset of auroral substorms }, journal={Journal of Geophysical Research}, volume={84}, number={A12}, year={1979}, month={Dec}, pages={7113-22}, abstract={ Observations of the aurora borealis were undertaken during the period August 10-20, 1976, from Fort Smith, Northwest Territories, Canada. Two auroral substorm 'breakup' events which occurred in the Alberta sector during this period were photographically documented and have been studied together with the associated polar magnetic substorm events. It is found that significant westward-directed ionospheric current flow occurs for perhaps 2 or 3 minutes prior to the appearance of the auroral breakup surge form. This current appears to lie parallel to the bright arc which forms before onset of the breakup phase. Such an observation is important relative to the timing of the onsets both of auroral and polar magnetic substorms }, keywords={ atmospheric electricity aurora ionosphere magnetic storms magnetic variation auroral substorm aurora borealis polar magnetic substorm ionosphere current AD 1976 08 10 to 20 breakup event atmosphere electricity }, mynotes={UNREAD}, } @ARTICLE{RantaAug78, title={ The onset of an auroral absorption substorm }, journal={Journal of Geophysical Research}, volume={83}, number={A8}, year={1978}, month={Aug}, pages={3893-9}, abstract={ The features of the breakup of an auroral absorption substorm are discussed. In the longitudinal sector where the substorm breaks up, a sharp onset is preceded by weak absorption which intensifies as it moves equatorward. The maximum value of absorption after the onset depends on the intensification of the equatorward-moving absorption preceding the breakup. On the basis of the studied substorms it seems that before the onset the weak absorption decreases having a minimum just before the onset and that at longitudes near the breakup a sharp onset can be seen without any preceding absorption, or the minimum of the absorption preceding the onset lasts longer }, keywords={ atmospheric movements aurora electromagnetic wave absorption magnetic storms magnetosphere magnetospheric electromagnetic wave propagation auroral absorption substorm longitudinal sector sharp onset weak absorption substorm breakup riometer data magnetic storms absorption maximum value absorption minimum equatorward moving absorption intensification ionospheric disturbance }, mynotes={UNREAD}, } @ARTICLE{ChangNov75, author={Chang, R.P.H. and Lanzerotti, L.J.}, title={ On the generation of magnetohydrodynamic waves at the onset of a substorm }, journal={Geophysical Research Letters}, volume={2}, number={11}, year={1975}, month={Nov}, pages={489-91}, abstract={ Theoretical analysis of magnetoacoustic waves driven unstable by a neutral charged-particle beam suggests that such waves can be generated in the plasma sheet at the onset of a substorm. It is further suggested that the magnetohydrodynamic waves observed to occur at the onset of substorms (often called Pi2 pulsations) may be attributed to the coupling of resonant field lines on the nightside of the Earth. Experimental determinations of the distribution of resonant field lines for various frequency components of the waves, together with the theoretical concepts, can ultimately yield information on the inward velocity of hot plasma particles at substorm onsets }, keywords={ magnetic storms magnetohydrodynamic waves magnetosphere micropulsations plasma magnetoacoustic waves plasma sheet Pi2 pulsations hot plasma particles substorm onsets magnetohydrodynamic waves generation neutral charged particle beam Earth nightside locally resonant field lines inward velocity field lines distribution field line reconnection magnetotail }, mynotes={UNREAD}, } @ARTICLE{KamideNov74, author={Kamide, Y. and McIlwain, C.E.}, title={ The onset time of magnetospheric substorms determined from ground and synchronous satellite records }, journal={Journal of Geophysical Research}, volume={79}, number={31}, year={1974}, month={Nov}, pages={4787-90}, abstract={ The result of the test to determine the onset time of magnetospheric substorms by examining the simultaneous ATS 5 particle and ground magnetic data is reported. It is found that for substorms of great intensity, their onset times inferred from the ground magnetic perturbations and from proton injections into the synchronous orbit coincide within an accuracy of 10 min. For weak and localized substorms, however, there is sometimes no particle injection into the ATS distance. It is suggested that the location of substorm origin in the magnetotail is at a greater geocentric distance for such weak substorms than it is for intense ones }, keywords={ magnetic storms magnetosphere onset time magnetospheric substorms ATS 5 ground magnetic perturbations: proton injections magnetotail }, mynotes={UNREAD}, } @ARTICLE{MaMay97, author={Ma, T.-Z. and Schunk, R.W.}, title={ Effect of sun-aligned arcs on the polar thermosphere }, journal={Journal of Geophysical Research}, volume={102}, number={A5}, year={1997}, month={May}, pages={9729-35}, abstract={ Sun-aligned polar cap arcs cause regions of enhanced ionization that often appear when the interplanetary magnetic field is near zero or northward. They are typically associated with a shear in the convection electric field, which leads to electron precipitation and plasma density enhancements that can be up to 10 times background plasma densities. The sun-aligned arcs are 100-300 km in width and 1000 km in length. Because the arcs offer resistance to the basically antisunward thermospheric flow, they could cause an appreciable thermospheric perturbation. To determine their effect, a time-dependent, three-dimensional, high-resolution model of the global thermosphere was used to calculate the thermospheric response to "representative" sun-aligned arcs. The model predicts that the largest perturbations occur when the arcs are associated with a sheared electric field and when multiple arcs are present. In this case, there are both density and temperature enhancements on the upstream side of the arcs and depressions on the downstream side. There is about a 20% neutral density variation and about a 100 K neutral temperature variation across the arcs }, keywords={ atmospheric electricity atmospheric movements aurora electron density interplanetary magnetic fields ionospheric disturbances solar wind thermosphere sun-aligned arcs polar thermosphere enhanced ionization interplanetary magnetic field polar cap arcs convection electric field electron precipitation plasma density enhancements antisunward thermospheric flow perturbation sheared electric field density temperature depressions enhancements upstream downstream }, mynotes={UNREAD}, } @ARTICLE{SinghJan97, author={Singh, N. and Leung, W.C. and Vashi, B.I.}, title={ Potential structure near a probe in a flowing magnetoplasma and current collection }, journal={Journal of Geophysical Research}, volume={102}, number={A1}, year={1997}, month={Jan}, pages={195-208}, abstract={ The distributions of plasma and potential near an electric probe in a relative motion with respect to a magnetized plasma are studied by means of three-dimensional (3D) numerical simulations. The relative motion is simulated by a plasma flowing past the probe across the ambient magnetic field. The plasma flow is imposed by a convection electric field E_/sub 0/. A probe with a positive potential bias is considered. The prominent features of the potential distribution include (1) wings of positive potential perturbations extending along the magnetic field and swept forward in the direction of the plasma flow and (2) a "fan" shaped structure in planes transverse to the magnetic field in the region where the convection electric field E_/sub 0/ is opposed by space charge electric fields. The wing-like structure can be interpreted in terms of electrostatic plasma waves belonging to the oblique resonance cone in a magnetized plasma. The relative flow causes the formation of a "bow shock" in front of the probe, where plasma density is enhanced due to the combined effect of the retardation of the flowing ions and the modification in the E_*B_ drift of the electrons in the sheath of a positive probe. The electron collection by the probe is significantly enhanced above the theoretical upper bound current obtained from the conservation of energy and the canonical angular momentum for the case without the relative motion. The current in the plasma, contributing to the collection of electrons by the probe, flows in a magnetic field-aligned channel in the vicinity of the probe where electric fields parallel to the magnetic field are relatively strong. Electron flux is fed into the channel all along its length by the E_*B_ drift in the self-consistent electric field, considerably enhancing the current collected by the probe. The field-aligned current channel is localized near the probe where parallel electric fields dominate; it does not extend to infinity along the probe's magneti }, keywords={ atmospheric measuring apparatus atmospheric techniques ionospheric measuring apparatus ionospheric techniques plasma probes ionosphere magnetosphere measurement technique plasma probe potential structure electric field flowing magnetoplasma electric current collection electric probe magnetized plasma three dimensional numerical simulation fan shaped structure wing-like structure electrostatic plasma wave field-aligned channel }, mynotes={UNREAD}, } @ARTICLE{KikuchiAug96, author={Kikuchi, T. and Luhr, H. and Kitamura, T. and Saka, O. and Schlegel, K.}, title={ Direct penetration of the polar electric field to the equator during a DP 2 event as detected by the auroral and equatorial magnetometer chains and the EISCAT radar }, journal={Journal of Geophysical Research}, volume={101}, number={A8}, year={1996}, month={Aug}, pages={17161-73}, abstract={ The quasi-periodic DP 2 magnetic fluctuations (period of 30-40 min) appearing coherently at the auroral and equatorial latitudes during the day are analyzed based on the high time resolution magnetometer data recorded at the International Monitor for Auroral Geomagnetic Effects (IMAGE) stations in Scandinavia and at the Brazilian and African equatorial stations. It is shown that the correlation between the DP 2 magnetic fluctuations at both latitudes is excellent (correlation coefficient of 0.9). No discernible time shift has been found within the resolution of 25 s. The European incoherent scatter (EISCAT) radar observations in Scandinavia show that the DP 2 fluctuations at auroral latitudes are caused by an ionospheric Hall current. At the equator, the DP 2 fluctuations are caused by a Pedersen current enhanced by the Cowling effect. Both of these effects are controlled by the convection electric field observed by the EISCAT radar }, keywords={ electric fields ionospheric disturbances magnetic storms polar electric field penetration DP 2 event quasiperiodic DP 2 magnetic fluctuations auroral magnetometer chains equatorial magnetometer chains EISCAT radar International Monitor for Auroral Geomagnetic Effects IMAGE stations Scandinavia Brazilian equatorial stations African equatorial stations European incoherent scatter radar observations auroral latitudes ionospheric Hall current Pedersen current Cowling effect convection electric field }, mynotes={UNREAD}, } @ARTICLE{KanMay96, author={Kan, J.R. and Deehr, C.S. and Lyu, L.H. and Newell, P.T.}, title={ Ionospheric signatures of patchy-intermittent reconnection at dayside magnetopause }, journal={Journal of Geophysical Research}, volume={101}, number={A5}, year={1996}, month={May}, pages={10939-45}, abstract={ Ionospheric signatures predicted by the patchy-intermittent (P-I) dayside reconnection model during southward interplanetary magnetic field are discussed. The P-I reconnection can lead to spiky convection electric fields. The spiky convection electric fields in turn drives enhanced convection channels on closed field lines in the dayside ionosphere. The observed convection speed in the enhanced convection channel ranges from À0.5 to À2 km/s. The P-I reconnection model also predicts that the dayside auroral forms should move noonward along enhanced convection channels. Poleward shift of dayside auroral forms occurs as the enhanced convection channels shift poleward due to reconfiguration of magnetic field following enhanced dayside reconnection. Multiple brightenings of dayside auroral forms should occur on a timescale of À2 to 4 min, equal to twice the Alfven bounce period between the ionosphere and the equatorial plane. Patchy reconnection is intrinsically intermittent due to the reconnection of elbow-shaped open flux tubes. The resulting reclosed flux tubes should contain a mixture of magnetosheath-magnetospheric plasmas as observed in the low-latitude boundary layer }, keywords={ ionosphere ionospheric disturbances magnetosphere solar wind solar wind magnetosphere interaction magnetosphere ionosphere coupling ionospheric signature patchy-intermittent reconnection dayside magnetopause dayside reconnection model southward interplanetary magnetic field IMF direction spiky convection electric field enhanced convection channel dayside ionosphere dayside auroral form poleward shift low-latitude boundary layer magnetosheath }, mynotes={UNREAD}, } @ARTICLE{MaynardApr96, author={Maynard, N.C. and Burke, W.J. and Basinska, E.M. and Erickson, G.M. and Hughes, W.J. and Singer, H.J. and Yahnin, A.G. and Hardy, D.A. and Mozer, F.S.}, title={ Dynamics of the inner magnetosphere near times of substorm onsets }, journal={Journal of Geophysical Research}, volume={101}, number={A4}, year={1996}, month={Apr}, pages={7705-36}, abstract={ The electrodynamics of the inner magnetosphere near times of substorm onsets have been investigated using CRRES measurements of magnetic and electric fields, energetic electron fluxes, in conjunction with ground-based observations. Six events were studied in detail, spanning the 2100 to 0000 MLT sector and L values from 5 to 7. In each case the dawn-dusk electric field was enhanced over typical background electric fields, and significant, low-frequency pulsation activity was observed. The amplitudes of the pulsations were larger than the background electric fields. Dusk-dawn excursions of the cross-tail electric field often correlated with changes in currents and particle energies at CRRES and with ULF wave activity observed on the ground. Variations of the electric field and Poynting vectors with periods in the Pi 2 range are consistent with bouncing Alfven waves that provide electromagnetic communication between the ionosphere and plasma sheet. Magnetic signatures of field-aligned current filaments directed away from the ionosphere, presumably associated with the substorm current wedge, were observed during three orbits. In all cases, ground signatures of substorm expansion were observed at least 5 min before the injection of electrons at CRRES. Field-aligned fluxes of counter-streaming, low-energy electrons were detected after three of the injections. The authors develop an empirical scenario for substorm onset. The process grows from ripples at the inner edge of the plasma sheet associated with dusk-dawn excursions of the electric field, prior to the beginning of dipolarization. Energy derived from the braking of the inward plasma convection flows into the ionosphere in the form of Poynting flux. Subsequently reflected Poynting flux plays a crucial role in the magnetosphere-ionosphere coupling. Substorms develop when significant energy (positive feedback?) flows in both directions, with the second cycle stronger than the initial. Pseudobreakups occur when energy }, keywords={ magnetic storms magnetosphere micropulsations inner magnetosphere substorm onset magnetic storm dynamics electrodynamics electric field magnetic field low-frequency pulsation activity cross-tail electric field magnetotail Poynting vector Pi 2 micropulsation bouncing Alfven wave ionosphere magnetosphere interaction plasma sheet ripples magnetosphere-ionosphere coupling pseudobreakup breakup explosive-growth-phase }, mynotes={UNREAD}, } @ARTICLE{AggsonMar96, author={Aggson, T.L. and Leakso, H. and Maynard, N.C. and Pfaff, R.F.}, title={ In situ observations of bifurcation of equatorial ionospheric plasma depletions }, journal={Journal of Geophysical Research}, volume={101}, number={A3}, year={1996}, month={Mar}, pages={5125-32}, abstract={ Vector electric field measurements from the San Marco D satellite are utilized to investigate the bifurcation of ionospheric plasma depletions (sometimes called "bubbles") associated with nightside equatorial spread F. These depletions are identified by enhanced upward E*B convection in depleted plasma density channels in the nighttime equatorial ionosphere. The in situ determination of the bifurcation process is based on dc electric field measurements of the bipolar variation in the zonal flow, westward and eastward, as the eastbound satellite crosses isolated signatures of updrafting plasma depletion regions. We also present data in which more complicated regions of zonal velocity variations appear as the possible result of multiple bifurcations of updrafting equatorial plasma bubbles }, keywords={ atmospheric electricity atmospheric movements F-region ionospheric disturbances bifurcation equatorial ionospheric plasma depletions electric field bubbles nightside equatorial spread F enhanced upward E*B convection depleted plasma density channels nighttime equatorial ionosphere zonal flow updrafting equatorial plasma bubbles }, mynotes={UNREAD}, } @ARTICLE{PinnockMay95, author={Pinnock, M. and Rodger, A.S. and Berkey, F.T.}, title={ High-latitude F region electron concentration measurements near noon: a case study }, journal={Journal of Geophysical Research}, volume={100}, number={A5}, year={1995}, month={May}, pages={7723-9}, abstract={ A case study is presented of a ridge of enhanced F region plasma in the afternoon sector near the equatorward edge of the auroral oval. The study for September 26, 1982, principally exploits data from three ionosondes near 62 degrees invariant latitude in the southern hemisphere separated by 5 1/2 hours of local time but only 3 1/2 hours of magnetic time. These observations demonstrate that the ridge structure is better ordered in magnetic time than in local time. Each station observes the ridge for about 4 hours. The poleward part of the ridge is rich in small-scale (1-10 km) ionospheric irregularities. It is suggested that the entire ridge is formed by the mechanism described by Foster (1993) in which plasma initially corotates past noon at lower latitudes, before being entrained in the convection pattern in the afternoon sector, and brought back toward noon. The plasma thus has an extended trajectory in sunlight leading to high concentrations. The irregularities probably result from the combined effects of high electric fields and energetic particle precipitation. The contribution which this plasma is likely to make to plasma structures in the polar cap is discussed briefly }, keywords={ F-region AD 1982 09 26 ionosphere F-region high latitude electron concentration noon midday ridge enhanced plasma afternoon sector equatorward edge auroral oval ridge structure ionospheric irregularities formation mechanism electric field energetic particle precipitation }, mynotes={UNREAD}, } @ARTICLE{WeissMay95, author={Weiss, L.A. and Reiff, P.H. and Weber, E.J. and Carlson, H.C. and Lockwood, M. and Peterson, W.K.}, title={ Flow-aligned jets in the magnetospheric cusp: results from the Geospace Environment Modeling Pilot program }, journal={Journal of Geophysical Research}, volume={100}, number={A5}, year={1995}, month={May}, pages={7649-59}, abstract={ Presents observations showing transient dayside auroral jets, associated with plasma flow enhancements, which behave in the same manner as that suggested for newly opened flux tubes; i.e., flow jets appear when mod B/sub y/ mod >B/sub z/ and are directed opposite to the direction of B/sub y/. A simple model of why the high-flow regions appear as elongated optical rays is suggested: under high-flow conditions (i.e., enhanced reconnection electric fields) ions injected at the merging point have a longer ground track V dt than those injected under slow-flow (background) conditions; due to the requirement of quasi-neutrality, the region of precipitating electron flux and thus 630.0-nm emission is also longer. It is significant that the flow jets are intermittent and transient, with durations of tens of minutes. The optical jets are interpreted as evidence of enhanced reconnection which, under northward IMF conditions, occurs predominantly when mod B/sub y/ mod >B/sub z/. The authors present a possible convection pattern, involving both dayside and lobe reconnection, which accounts for the reversed ion dispersion seen by DE 1 in conjunction with the strong westerly flow. It is suggested that if periods of enhanced reconnection occur at these locations, the duration of the reconnection is less than the duration of the flow-aligned jets, which varies between 5 and 25 min. Given that the precipitation within the jets lasts for >or=8 min, the authors conclude that the reconnection pulses last for approximately 0-17 min. One must keep in mind, however, that little direct evidence exists which links the transient dayside ionospheric phenomena discussed }, keywords={ airglow atmospheric elementary particle precipitation atmospheric movements ionosphere magnetosphere plasma magnetospheric cusp Geospace Environment Modeling Pilot program flow-aligned jets transient dayside auroral jets plasma flow enhancements newly opened flux tubes high-flow regions elongated optical rays enhanced reconnection electric fields merging point slow-flow conditions quasi-neutrality precipitating electron flux convection pattern dayside reconnection lobe reconnection reversed ion dispersion strong westerly flow transient dayside ionospheric phenomena 630.0-nm emission 630.0 nm }, mynotes={UNREAD}, } @ARTICLE{Xiaoming-ZhuFeb95, title={ How the magnetosphere is driven into the substorm }, journal={Journal of Geophysical Research}, volume={100}, number={A2}, year={1995}, month={Feb}, pages={1847-56}, abstract={ This paper puts together several aspects of the substorm phenomena into a scenario subject to quantitative analysis, based on Ampere's law, magnetic stresses, and the effect of the parallel electric field. As the magnetospheric convection continuously shears the magnetic field, the parallel electric field suddenly switches on when the shear reaches a critical value. The parallel electric field not only accelerates the charged particles to cause the auroral display but also partially decouples the ionosphere from the magnetosphere so that the magnetospheric convection is enhanced significantly, causing the substorm expansion phase. Pi 2 pulsations are excited by the change of the magnetosphere-ionosphere coupling. The authors show a direct relationship between the parallel potential drop, the enhanced convection rate, and the amplitude of the Pi 2 pulsations. With no adjustable parameter, the relationship shows quantitative agreement with the diverse observations }, keywords={ ionosphere magnetic storms micropulsations magnetosphere magnetic substorm magnetic storm initiation generation formation model scenario quantitative analysis Ampere's law magnetic stress parallel electric field plasma convection magnetic field shear substorm expansion phase Pi 2 magnetosphere-ionosphere coupling magnetic pulsation micropulsation }, mynotes={UNREAD}, } @ARTICLE{NilssonAug94, author={Nilsson, H. and Kirkwood, S. and Eliasson, L. and Norberg, O. and Clemmons, J. and Boehm, M.}, title={ The ionospheric signature of the cusp: a case study using Freja and the Sondrestrom radar }, journal={Geophysical Research Letters}, volume={21}, number={17}, year={1994}, month={Aug}, pages={1923-6}, abstract={ Radar measurements in the cusp region, in close conjunction with the Freja satellite, show evidence of the ionospheric signature of the cusp. The intense low-energy fluxes of ions and electrons associated with the cusp, and seen with the satellite, produce a distinct region of enhanced electron density and electron temperature in the ionospheric F-region. The ionization due to the precipitating ions is rather weak, of the same order of magnitude, and maximizing at the same altitude, as the solar EUV ionization. That due to the electrons is much stronger, maximizes at higher altitude and is clearly identifiable in this case. This is partly because of the unusually high altitude of the cold, EUV and convection controlled F-region, creating a distinct height difference as compared to the precipitation region, and partly because ion outflow prevents the cold daytime plasma from convecting into the precipitation region. A narrow region of high ion temperatures most likely indicating strong electric fields is seen within the precipitation region but is not coincident with the most intense precipitation. The equatorward boundary of the precipitation region is seen to move equatorward, while the convection of the plasma within the region is poleward }, keywords={ atmospheric ion precipitation ionosphere remote sensing by radar ionospheric signature polar cusp region Sondrestrom radar measurements Freja satellite observations ion fluxes electron fluxes enhanced electron density electron temperature ionospheric F-region precipitating ions solar EUV ionization convection controlled F-region ion outflow cold daytime plasma precipitation region equatorward boundary ion temperatures plasma convection }, mynotes={UNREAD}, } @ARTICLE{SchunkAug94, author={Schunk, R.W. and Zhu, L. and Sojka, J.J.}, title={ Ionospheric response to traveling convection twin vortices }, journal={Geophysical Research Letters}, volume={21}, number={17}, year={1994}, month={Aug}, pages={1759-62}, abstract={ Traveling convection twin vortices have been observed for several years. At ionospheric altitudes, the twin vortices correspond to spatially localized, transient structures embedded in a large-scale background convection pattern. The convection vortices are typically observed in the morning and evening regions. They are aligned predominantly in the east-west direction and have a horizontal extent of from 500-1000 km. Associated with the twin vortices are enhanced electric fields, particle precipitation, and an upward/downward field-aligned current pair. Once formed, the twin vortex structures propagate in the tailward direction at speeds of several km/s, but they weaken as they propagate and only last for about 10-20 minutes. Because these convection structures might have a significant effect on the localized ionosphere, the USU ionospheric model was used to calculate the response of the ionosphere to "representative" traveling convection twin vortices for a range of background conditions. The ionospheric response includes localized temperature enhancements, ion composition changes, non-Maxwellian ion distributions, and plasma upwelling events. The response is transient and the magnitude of the response depends on the background ionospheric conditions and on the characteristics of the twin vortices }, keywords={ atmospheric electricity atmospheric elementary particle precipitation ionosphere magnetosphere traveling convection twin vortices spatially localized transient structures large-scale background convection pattern morning evening electric fields particle precipitation upward/downward field-aligned current pair response temperature enhancements ion composition nonMaxwellian ion distributions plasma upwelling }, mynotes={UNREAD}, } @ARTICLE{RodgerApr94, author={Rodger, A.S. and Pinnock, M. and Dudeney, J.R. and Baker, K.B. and Greenwald, R.A.}, title={ A new mechanism for polar patch formation }, journal={Journal of Geophysical Research}, volume={99}, number={A4}, year={1994}, month={Apr}, pages={6425-36}, abstract={ Polar patches are regions within the polar cap where the F-region electron concentration and airglow emission at 630 nm are enhanced above a background level. Polar patches can be readily identified in Polar Angle-American Conjugate Experiment (PACE) data. PACE data and those from complementary instruments are used to show that some polar patches form in the dayside cusp within a few minutes of the simultaneous occurrence of a flow channel event and azimuthal flow changes in the ionospheric convection pattern. The latter are caused by variations of the IMF y-component. The physical processes by which these phenomena cause plasma enhancements and depletions in the vicinity of the dayside cusp and cleft are discussed. Subsequently, these features are transported into the polar cap where they continue to evolve. The spatial scale of patches when formed is usually 200-1000 km in longitude and 2 degrees -3 degrees wide in latitude. Their motion after formation and the velocity of the plasma within the patches are the same, indicating that they are drifting under the action of an electric field. Occasionally, patches are observed to occur simultaneously in geomagnetic conjugate regions. Since some of these observations are incompatible with the presently-accepted model for patch formation involving the expansion of the high latitude convection pattern entraining solar-produced plasma, further modeling of the effects of energetic particle precipitation in the cusp, the consequences of flow channel events on the plasma concentrations, and the time dependence of plasma convection as a result of interplanetary magnetic field by changes is recommended }, keywords={ atmospheric structure F-region plasma polar patch formation F-region electron concentration airglow emission polar cap Polar Angle-American Conjugate Experiment PACE dayside cusp flow channel azimuthal flow changes IMF y-component cleft spatial scale electric field energetic particle precipitation time dependence interplanetary magnetic field 630 nm }, mynotes={UNREAD}, } @ARTICLE{GonzalezApr94, author={Gonzalez, W.D. and Joselyn, J.A. and Kamide, Y. and Kroehl, H.W. and Rostoker, G. and Tsurutani, B.T. and Vasyliunas, V.M.}, title={ What is a geomagnetic storm? }, journal={Journal of Geophysical Research}, volume={99}, number={A4}, year={1994}, month={Apr}, pages={5771-92}, abstract={ After a brief review of magnetospheric and interplanetary phenomena for intervals with enhanced solar wind-magnetosphere interaction, an attempt is made to define a geomagnetic storm as an interval of time when a sufficiently intense and long-lasting interplanetary convection electric field leads, through a substantial energization in the magnetosphere-ionosphere system, to an intensified ring current sufficiently strong to exceed some key threshold of the quantifying storm time Dst index. The associated storm/substorm relationship problem is also reviewed. Although the physics of this relationship does not seem to be fully understood at this time, basic and fairly well established mechanisms of this relationship are presented and discussed. Finally, toward the advancement of geomagnetic storm research, some recommendations are given concerning future improvements in monitoring existing geomagnetic indices as well as the solar wind near Earth }, keywords={ magnetic storms solar wind solar wind magnetosphere interaction substorm magnetic storm definition geomagnetic storm interplanetary convection electric field intensified ring current Dst index }, mynotes={UNREAD}, } @ARTICLE{EgelandFeb94, author={Egeland, A. and Burke, W.J. and Maynard, N.C. and Basinska, E.M. and Winningham, J.D. and Deehr, C.S.}, title={ Ground and satellite observations of postdawn aurorae near the time of a sudden storm commencement }, journal={Journal of Geophysical Research}, volume={99}, number={A2}, year={1994}, month={Feb}, pages={2095-108}, abstract={ Meridian scanning photometer measurements taken in the magnetic postdawn sector at Longyearbyen, Svalbard, between 0300 and 0630 UT on December 29, 1981, are analyzed in conjunction with particle and field data retrieved during two near passes of the DE 2 satellite. The interval included a sudden storm commencement (SSC). Pre-SSC optical and particle measurements showed a system of arcs that are spaced at approximately 1.1 degrees intervals in magnetic latitude, embedded within the region 1 current system and span the convection reversal. The softer particle precipitation appears to have a source near the flanks of the magnetotail while the harder, more equatorward precipitation originates closer to Earth. During the SSC period the entire sky brightened, with enhanced 630.0-nm emissions extending from the northern horizon to south of magnetic zenith; intense but spatially separated 557.7-nm emissions dominated the southern horizon. DE 2 detected a more than an order of magnitude increase and near isotropization of ring current electron fluxes, enhanced precipitation from the plasma sheet and significantly decreased auroral zone convection. Region 1/region 2 currents remained, with wavelike structures superposed. On few minute travel timescales for hydromagnetic waves to pass through the system, magnetospheric particles accelerate and precipitate to increase the ionospheric conductivity. Global, field-aligned currents change more slowly. To maintain similar field-aligned currents with higher ionospheric conductances requires reduced electric fields. After 0520 UT the optical emissions settled into stable, but latitudinally separated, bands of 630.0- and 557.7-nm emissions }, keywords={ atmospheric electricity atmospheric elementary particle precipitation aurora magnetic storms magnetosphere postdawn aurorae sudden storm commencement satellite observations meridian scanning photometer measurements magnetic postdawn sector DE 2 satellite arcs region 1 current system convection reversal particle precipitation magnetotail ring current electron fluxes plasma sheet auroral zone convection region 2 currents wavelike structures hydromagnetic waves magnetospheric particles ionospheric conductivity field-aligned currents optical emissions AD 1981 12 29 557.7 nm 630.0 nm }, mynotes={UNREAD}, } @ARTICLE{SojkaSep93, author={Sojka, J.J. and Bowline, M.D. and Schunk, R.W. and Decker, D.T. and Valladares, C.E. and Sheehan, R. and Anderson, D.N. and Heelis, R.A.}, title={ Modeling polar cap F-region patches using time varying convection }, journal={Geophysical Research Letters}, volume={20}, number={17}, year={1993}, month={Sep}, pages={1783-6}, abstract={ The creation of polar cap F-region patches is simulated using two independent physical models of the high-latitude ionosphere. The patch formation is achieved by temporally varying the magnetospheric electric field (ionospheric convection) input to the models. The imposed convection variations are comparable to the changes in the convection that result from changes in the B/sub y/ IMF component for southward interplanetary magnetic field (IMF). Solar maximum-winter simulations show that simple changes in the convection pattern lead to significant changes in the polar cap plasma structuring. Specifically, in winter, as enhanced dayside plasma convects into the polar cap to form the classic tongue-of-ionization (TOI), the convection changes produce density structures that are indistinguishable from the observed patches }, keywords={ atmospheric electricity atmospheric ionisation atmospheric movements F-region interplanetary magnetic fields ionosphere magnetosphere plasma dayside plasma poleward convection aeronomy enhanced ionisation patches antisunward drift solar wind-magnetosphere coupling plasma density structures magnetosphere-ionosphere coupling plasma flow changes interplanetary magnetic field B/sub y/-component solar maximum winter simulations polar cap F-region patches time varying convection high-latitude ionosphere magnetospheric electric field ionospheric convection southward interplanetary magnetic field polar cap plasma structuring tongue-of-ionization }, mynotes={UNREAD}, } @ARTICLE{ShueJan94, author={Shue, J.-H. and Weimer, D.R.}, title={ The relationship between ionospheric convection and magnetic activity }, journal={Journal of Geophysical Research}, volume={99}, number={A1}, year={1994}, month={Jan}, pages={401-15}, abstract={ It is shown that there is a significant relationship between magnetic activity and high-latitude ionospheric convection electric fields. In particular, when the westward electrojet is much stronger than the eastward electrojet, as occurs during magnetospheric substorms, the electric field patterns show subtle, but important, changes from the configurations that are obtained under more quiet conditions. The substorm differences are detected primarily near midnight, where there is an enhanced westward electric field associated with a penetration of the positive-potential, dawn convection cell into the negative, dusk convection cell. The peak value of the positive potential also increases during substorms and its location shifts closer to midnight, while the negative cell remains relatively constant. These results were obtained through the use of a procedure that uses electric field measurements from the DE 2 satellite to derive maps of the locations of the convection reversal boundaries, and functions for the distribution of the electric potential around these boundaries. This was accomplished for several sets of data that were grouped according to the IMF and geomagnetic activity. Distortions of the electric field patterns near midnight are simply the result of polarization electric fields around conductivity enhancements. The distorted electric fields satisfy the condition that the ionospheric Hall current be divergence-free }, keywords={ ionosphere ionosphere plasma flow westward electrojet magnetic activity high-latitude convection electric field eastward electrojet electric field pattern substorm magnetic storm disturbance westward electric field dawn convection cell dusk convection cell Hall current divergence-free }, mynotes={UNREAD}, } @ARTICLE{FosterFeb93, title={ Storm time plasma transport at middle and high latitudes }, journal={Journal of Geophysical Research}, volume={98}, number={A2}, year={1993}, month={Feb}, pages={1675-89}, abstract={ The author presents observations which locate and identify the ionospheric feature which constitutes the storm time ionospheric dusk effect in both latitude and local time and show its clear relationship to sunward E*B convection. Simultaneous two-dimensional mapping of the convection pattern and ionospheric density shows the continuity of this convecting plasma feature between its mid- or low-latitude source region and the cleft and polar cap at high latitude. It is shown that the latitude of occurrence of this feature has a clear and repeatable dependence on the storm time disturbance level, as measured by Kp, that can be explained by the equatorward expansion of the region of sunward convection electric field during storms. The offset of the geomagnetic and geographic poles combines with the shape of the convection pattern in magnetic coordinates and the Earth's rotation to create the storm time dusk effect at mid-latitudes and a low-latitude source for the enhanced plasma found in the polar cap and at nightside auroral latitudes during disturbed magnetic conditions }, keywords={ atmospheric electricity F-region ionosphere plasma plasma transport high latitudes storm time ionospheric dusk effect sunward E*B convection two-dimensional mapping convection pattern density cleft polar cap equatorward expansion electric field mid-latitudes }, mynotes={UNREAD}, } @ARTICLE{DelcourtNov92, author={Delcourt, D.C. and Moore, T.E. and Sauvaud, J.A. and Chappell, C.R.}, title={ Nonadiabatic transport features in the outer cusp region }, journal={Journal of Geophysical Research}, volume={97}, number={A11}, year={1992}, month={Nov}, pages={16833-42}, abstract={ The dayside to nightside circulation of plasma along the magnetopause inside the magnetosphere is examined by means of three-dimensional single-particle codes. It is demonstrated that particles incident upon the outer cusp region experience transient non-adiabatic motions, owing to a localized minimum in the field magnitude. Here, possibly large magnetic moment changes yield injection into the loss cone of fractions of the incoming population or, alternatively, enhanced bouncing motions at high altitudes. It is shown that particles gaining access to the magnetotail over the polar cap are progressively extracted from the weak field region by the large-scale convection electric field. In this latter case, the trajectory simulations suggest an implicit 'entry boundary' into the nightside magnetosphere }, keywords={ magnetosphere nonadiabatic transport plasma flow magnetosphere 3D model trapped particle motion outer cusp region dayside to nightside circulation magnetopause three-dimensional single-particle codes magnetotail trajectory simulations }, mynotes={UNREAD}, } @ARTICLE{NemzekJul91, author={Nemzek, R.J. and Winckler, J.R.}, title={ Parallel electric fields detected via conjugate electron echoes during the Echo 7 sounding rocket flight }, journal={Journal of Geophysical Research}, volume={96}, number={A7}, year={1991}, month={Jul}, pages={11475-83}, abstract={ Electron detectors on the Echo 7 active sounding rocket experiment measured 'conjugate echoes' resulting from artificial electron beam injections. Analysis of the electron drift motion after a complete bounce led to measurements of the magnetospheric convection electric field mapped to ionospheric altitudes. The magnetospheric field was highly variable, changing by tens of millivolts per meter on time scales of as little as hundreds of milliseconds. Sets of double probes on the payload measured the ionospheric electric field directly. While the smallest-scale magnetospheric field irregularities were damped out by ionospheric conductivity, larger-scale features were enhanced by up to 50 mV/m in the ionosphere. The mismatch between magnetospheric and ionospheric convection fields indicates a violation of the equipotential field line condition }, keywords={ ionosphere magnetosphere radiation belts magnetosphere parallel electric field ionosphere radiation belt trapped electrons conjugate electron echoes artificial electron beam injections electron drift motion convection electric field }, mynotes={UNREAD}, } @ARTICLE{KanJan91, title={ Dipolarization: a consequence of substorm expansion onset }, journal={Geophysical Research Letters}, volume={18}, number={1}, year={1991}, month={Jan}, pages={57-60}, abstract={ Dipolarization observed in the near-Earth plasma sheet can be initiated by the substorm expansion onset. Field-aligned currents at the substorm expansion onset are enhanced first in the ionosphere in response to an enhanced magnetospheric convection. Closure of substorm field-aligned currents through the plasma sheet can disrupt the cross-tail current to cause dipolarization in the plasma sheet. The electric field induced by the current disruption can launch a fast-mode compression wave to result in the plasma injection event. A new X line can form tailward of the dipolarization region during the substorm expansion phase. A timing sequence of substorm events is inferred from the proposed conceptual model of substorms based on the magnetosphere-ionosphere coupling process on the Alfven bounce time scale }, keywords={ magnetic storms magnetosphere dipolarization magnetosphere magnetic storm dipole substorm expansion onset near-Earth plasma sheet }, mynotes={UNREAD}, } @ARTICLE{ReddyDec90, author={Reddy, C.A. and Nishida, A. and Fukao, S. and Somayajulu, V.V.}, title={ Magnetospheric substorm-related electric fields in the ionosphere: discrepancy of an observation with model predictions }, journal={Geophysical Research Letters}, volume={17}, number={13}, year={1990}, month={Dec}, pages={2333-6}, abstract={ Theoretical models of disturbance electric fields in the middle and low latitude ionosphere have successfully explained several observed characteristics of the above electric fields. The models generally predict a large westward electric field in the 2300-0400 LT sector; but a recent study (Kamide and Baumjohann, 1985) of a major F-region disturbance at mid-latitudes revealed a large eastward electric field in the midnight-to-morning sector, during a magnetospheric substorm. This discrepancy indicates that processes additional to those considered in the models so far are playing an important role during substorms. One possible process is the generation of large, secondary ionospheric electric fields in and around the auroral zone due to the interplay of the spatially varying and time-varying enhanced conductivities, currents and electric fields during substorms. A second process may be the generation of large secondary electric fields in the inner magnetosphere due to the large spatial gradients of particle drifts during the substorm-time unsteady convection }, keywords={ atmospheric electricity ionosphere magnetic storms magnetosphere atmosphere electric fields ionosphere F-region disturbance magnetospheric substorm conductivities currents spatial gradients particle drifts unsteady convection }, mynotes={UNREAD}, } @ARTICLE{KanDec90, author={Kan, J.R. and Iijima, T. and Akasofu, S.-I.}, title={ A model of coupled radial and azimuthal current loops associated with substorms }, journal={Journal of Geophysical Research}, volume={95}, number={A12}, year={1990}, month={Dec}, pages={21291-5}, abstract={ The authors propose a model of the substorm current system in terms of coupled radial and azimuthal current loops. The polarization electric field is shown to be greater than the Cowling field, indicating that the net current in the radial current loop must be driven by the azimuthal pressure gradient in the central plasma sheet. The current in the radial current loop is shown to decrease or unchanged by an enhanced magnetospheric convection. On the other hand, the current in the azimuthal current loop is shown to increases with the enhanced convection. The decrease of the current in the radial current loop combined with the increase of the current in the azimuthal current loop associated with an enhanced magnetospheric convection can lead to the formation of the substorm current wedge which is known to occur during the expansion phase of substorms }, keywords={ atmospheric electricity magnetic storms magnetic substorm azimuthal current loops substorm current system polarization electric field Cowling field radial current loop azimuthal pressure gradient central plasma sheet magnetospheric convection current wedge expansion phase }, mynotes={UNREAD}, } @ARTICLE{DelcourtDec90, author={Delcourt, D.C. and Sauvaud, J.A. and Pedersen, A.}, title={ Dynamics of single-particle orbits during substorm expansion phase }, journal={Journal of Geophysical Research}, volume={95}, number={A12}, year={1990}, month={Dec}, pages={20853-65}, abstract={ Features of ion trajectories during 'taillike' to 'dipolelike' magnetic transitions are examined by means of three-dimensional particle codes. It is demonstrated that the large electric fields induced by the 'collapse' of the geomagnetic tail result in enhanced earthward convection of the midtail ( approximately 10 R/sub E/) magnetospheric populations. It is shown that the particle motion is controlled, to a major extent, by drifts that are negligible in steady state, namely, (1) in the direction parallel to the magnetic field, a centrifugal acceleration related to the rapid E*B transport, which can account for creation of new high-altitude mirror points, (2) perpendicularly to the magnetic field, a drift of polarization which possibly yields 'frozen-in' violation and transient breaking of the first adiabatic invariant }, keywords={ magnetic storms magnetosphere radiation belts magnetosphere trapped particle dynamics radiation belt taillike to dipolelike magnetic transition magnetotail collapse single-particle orbits substorm expansion phase ion trajectories three-dimensional particle codes large electric fields enhanced earthward convection particle motion centrifugal acceleration high-altitude mirror points }, mynotes={UNREAD}, } @ARTICLE{FosterOct88, author={Foster, J.C. and Aarons, J.}, title={ Enhanced antisunward convection and F region scintillations at mid-latitudes during storm onset }, journal={Journal of Geophysical Research}, volume={93}, number={A10}, year={1988}, month={Oct}, pages={11537-42}, abstract={ Millstone Hill radar observations over a wide span of latitudes detail the onset of 300 m/s antisunward (westward) convection at mid and low latitudes in the morning sector as a region of storm-enhanced sunward convection retreats poleward. Ring current observations reported by Lui et al. (1987) suggest that the magnetospheric shielding layer was coincident with the observed reversal between sunward and antisunward convection. A strong southward component of the F region neutral wind is observed at latitudes equatorward of the convection reversal. The authors' observations show the growth of the subauroral electric field as the shielding boundary moves poleward. They observed 136-MHz scintillations in both the auroral sunward convection region and the region of subauroral antisunward convection when the convection electric fields exceed 5 mV/m }, keywords={ F-region ionospheric electromagnetic wave propagation magnetic storms magnetosphere radiowave propagation magnetosphere ionosphere scintillation magnetic storm disturbance radiowave propagation F-region middle latitude enhanced antisunward convection plasma flow VHF during storm onset onset low latitudes morning sector storm-enhanced shielding boundary 136-MHz 136 MHz }, mynotes={UNREAD}, } @ARTICLE{KanJun88, title={ A theory of patchy and intermittent reconnections for magnetospheric flux transfer events }, journal={Journal of Geophysical Research}, volume={93}, number={A6}, year={1988}, month={Jun}, pages={5613-23}, abstract={ Proposes that the elbow-shaped flux transfer events (FTEs) of Russell and Elphic (1979) are initiated by a specific normal mode of three-dimensional tearing of the magnetopause current sheet, resulting in a three-dimensional component reconnection driven by the solar wind. The patchy nature of the proposed three-dimensional tearing on the dayside magnetopause, leading to isolated reconnection sites. Magnetic field signatures of the 3DT reconnection, and electric fields associated with the elbow-shaped FTEs are discussed. The electric field is expected to produce channels of enhanced magnetospheric convection. The observed multiple field-aligned current sheets and auroral arcs fanning out from the cusp region along enhanced convection channels are also considered together with the polar cap potential due to the elbow-shaped FTEs }, keywords={ interplanetary magnetic fields magnetosphere solar wind atmosphere interplanetary patchy reconnection intermittent reconnection magnetospheric flux transfer events elbow-shaped flux transfer events three-dimensional tearing magnetopause current sheet three-dimensional component reconnection solar wind dayside electric fields convection field-aligned current sheets auroral arcs cusp region polar cap potential }, mynotes={UNREAD}, } @ARTICLE{FosterOct84, author={Foster, J.C. and Doupnik, J.R.}, title={ Plasma convection in the vicinity of the dayside cleft }, journal={Journal of Geophysical Research}, volume={89}, number={A10}, year={1984}, month={Oct}, pages={9107-13}, abstract={ The Chatanika, Alaska, incoherent scatter radar has observed the ionospheric convection pattern equatorward of the noontime cleft. There plasma transport is characterized by low-speed convergence toward a meridian centered somewhat before noon and rotation of the flow into a poleward direction at higher latitudes. For undisturbed conditions there is only weak convection at noon at these latitudes, but the eastward electric field reaches a maximum of 15 mV/m 2-4 hours before and after noon at latitudes between 70 degrees Lambda and 74 degrees Lambda . During active conditions at the peak of the solar cycle poleward flow occurred over a 3-4 hour spread of local time. For disturbed conditions, the prenoon and postnoon regions of plasma entry into the polar cap were enhanced, and an eastward electric field of 25 mV/m was seen across the 2 hours of local time around noon }, keywords={ atmospheric electricity atmospheric movements atmospheric structure ionosphere plasma solar-terrestrial relationships transport processes ionosphere plasma convection high latitude ionosphere polar cap atmospheric movements prenoon entry region atmospheric electricity plasma flow poleward rotation Chatanika incoherent scatter radar postnoon region disturbed geomagnetic conditions solar maximum solar-terrestrial relationships AD 1977 to 1981 F-region plasma atmospheric structure dayside cleft Alaska ionospheric convection pattern noontime cleft plasma transport low-speed convergence undisturbed conditions weak convection eastward electric field solar cycle poleward flow local time noon }, mynotes={UNREAD}, } @ARTICLE{BarbosaFeb84, title={ Fourier analysis of polar cap electric field and current distributions }, journal={Journal of Geophysical Research}, volume={89}, number={A2}, year={1984}, month={Feb}, pages={867-75}, abstract={ A theoretical study of high-latitude electric fields and currents, using analytic fourier analysis methods, is conducted. A two-dimensional planar model of the ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. Two separate topics are treated. A field-aligned current element near the cusp region of the polar cap is included to investigate the modifications to the convection pattern by the east-west component of the interplanetary magnetic field. The second topic is concerned with the electric field configuration obtained in the limit of perfect shielding, where the field is totally excluded equatorward of the auroral oval }, keywords={ atmospheric electricity atmospheric movements interplanetary magnetic fields ionosphere magnetosphere plasma solar wind magnetosphere solar wind atmosphere movement plasma Fourier analysis polar cap electric field current distributions high-latitude two-dimensional planar model ionosphere enhanced conductivity auroral belt field-aligned currents cusp region interplanetary magnetic field auroral oval }, mynotes={UNREAD}, } @ARTICLE{KanApr84, author={Kan, J.R. and Williams, R.L. and Akasofu, S.-I.}, title={ A mechanism for the westward traveling surge during substorms }, journal={Journal of Geophysical Research}, volume={89}, number={A4}, year={1984}, month={Apr}, pages={2211-16}, abstract={ It is proposed that the westward traveling surge is formed as a result of a partial blockage of the substorm-enhanced Hall current from closure in the magnetosphere. The partial blockage of the enhanced Hall current leads to a buildup of 'excess' charge in the ionosphere that in turn produces a polarization electric field. The authors show that the resulting ionospheric electric field exhibits the characteristic distortion of the convection pattern associated with substorms. The distortion of the convection streamlines intrudes westward; the westward traveling surge is an optical manifestation of this intrusion. The speed of the westward traveling surge is identified with the speed of the charge spread }, keywords={ atmospheric electricity atmospheric movements ionosphere magnetic storms magnetosphere atmosphere movement plasma westward traveling surge substorms substorm-enhanced Hall current magnetosphere ionosphere polarization electric field convection pattern charge spread }, mynotes={UNREAD}, } @ARTICLE{LuhmannDec83, author={Luhmann, J.G. and Johnson, R.M. and Baron, M.J. and Balsley, B.B. and Riddle, A.C.}, title={ Observations of the high-latitude ionosphere with the Poker Flat MST radar: analyses using simultaneous Chatanika radar measurements }, journal={Journal of Geophysical Research}, volume={88}, number={A12}, year={1983}, month={Dec}, pages={10239-45}, abstract={ The NOAA MST (mesosphere-stratosphere-troposphere) VHF radar at Poker Flat, Alaska, provides nearly continuous high time resolution measurements of the velocity of 3-m scale plasma density irregularities at altitudes approximately 85 km during the summer and less continuous but lower ( approximately 65 km) altitude observations during the winter. However, incomplete knowledge of the origin and behavior of the VHF scatterers limits the applications of these data. Observations from the nearby Chatanika incoherent scatter radar are used to investigate the effects of electron precipitation and magnetospheric convection electric fields on the VHF observations. It is shown that the backscattered VHF signal is usually enhanced when auroral particles increase the D region ionization }, keywords={ ionosphere ionospheric electromagnetic wave propagation ionospheric techniques ionosphere plasma dynamics flow technique D-region radiowave high-latitude Poker Flat MST radar Chatanika radar measurements VHF radar Alaska velocity 3-m scale plasma density irregularities incoherent scatter radar backscattered }, mynotes={UNREAD}, } @ARTICLE{SchunkSep82, author={Schunk, R.W. and Sojka, J.J.}, title={ Ionospheric hot spot at high latitudes }, journal={Geophysical Research Letters}, volume={9}, number={9}, year={1982}, month={Sep}, pages={1045-8}, abstract={ A hot spot (or spots) can occur in the high-latitude ionosphere depending on the plasma convection pattern. The hot spot corresponds to a small magnetic local time-magnetic latitude region of elevated ion temperatures located near the dusk and/or dawn meridians. For asymmetric convection electric field patterns, with enhanced flow in either the dusk or dawn sector of the polar cap, a single hot spot should occur in association with the strong convection cell. However, on geomagnetically disturbed days, two strong convection cells can occur and, hence, two hot spots should exist. The hot spot should be detectable when the electric field in the strong convection cell exceeds about 40 mV m/sup -/1. For electric fields of the order of 100 mV m/sup -1/ in the convection cell, the ion temperature in the hot spot is greatest at low altitudes, reaching 4000K at 160 km, and decreases with altitude in the F-region. An ionospheric hot spot (or spots) can be expected at all seasons and for a wide range of solar cycle conditions }, keywords={ atmospheric movements F-region ionosphere high latitude ionosphere plasma convection three dimensional model F-region hot spot elevated ion temperatures flow }, mynotes={UNREAD}, } @ARTICLE{KanSep82, author={Kan, J.R. and Longenecker, D.U. and Olson, J.V.}, title={ A transient response model of Pi 2 pulsations }, journal={Journal of Geophysical Research}, volume={87}, number={A9}, year={1982}, month={Sep}, pages={7483-8}, abstract={ A transient response model of Pi 2 pulsations due to an enhanced convection in the plasma sheet is presented. A nonlinear Alfven wave is launched by the enhanced convection electric field. The reflection coefficient at the ionosphere is derived by matching the field-aligned current of the Alfven wave to the field-aligned current from the divergence of the ionospheric Hall and Pedersen currents. The resulting transient magnetic perturbation on the ground exhibits the characteristics of the Pi 2 pulsation signature accompanying a substorm onset. The predicted fundamental period of the magnetic perturbation is 4 times the one-way Alfven travel time which increases toward higher latitude. The predicted Pi 2 source regions in the ionosphere are in reasonable agreement with observations }, keywords={ micropulsations magnetic pulsation micropulsation generation transient response model Pi 2 enhanced convection plasma sheet nonlinear Alfven wave }, mynotes={UNREAD}, } @ARTICLE{BanksAug81, author={Banks, P.M. and Foster, J.C. and Doupnik, J.R.}, title={ Chatanika radar observations relating to the latitudinal and local time variations of Joule heating }, journal={Journal of Geophysical Research}, volume={86}, number={A8}, year={1981}, month={Aug}, pages={6869-78}, abstract={ Observations of plasma convection made with the Chatanika incoherent scatter radar have been analyzed to give latitude/local time plots of the electric field contribution (E/sup 2/) to thermospheric Joule heating. The data, which span the latitude range 56 degrees to 75 degrees Lambda , show the presence of strong heating throughout the auroral regions. Of special interest are brief interludes of intense heating (>50 mW m/sup -2/) that are observed at nearly all local times and latitudes in response to magnetospheric disturbances. Further, there seem to be particular regions of the auroral oval where Joule heating seems to be continually enhanced above the broad background. The results of six 24 hour experiments are presented to illustrate summer and winter conditions }, keywords={ atmospheric electricity atmospheric thermodynamics ionosphere plasma thermosphere atmosphere thermodynamics thermosphere atmosphere electricity ionosphere AD 1980 07 12 to 13 local time variations Joule heating plasma convection incoherent scatter radar electric field auroral regions magnetospheric disturbances auroral oval }, mynotes={UNREAD}, } @ARTICLE{SojkaOct79, author={Sojka, J.J. and Raitt, W.J. and Schunk, R.W.}, title={ Effect of displaced geomagnetic and geographic poles on high-latitude plasma convection and ionospheric depletions }, journal={Journal of Geophysical Research}, volume={84}, number={A10}, year={1979}, month={Oct}, pages={5943-51}, abstract={ It was assumed that the ionospheric plasma at high latitudes has a tendency to corotate about the geographic pole and that magnetospheric convection is relative to the geomagnetic pole. With this assumption plasma drift patterns over the polar cap were calculated for a range of constant magnetospheric electric fields as well as for asymmetric electric fields with enhanced plasma flow on either the dawnside of the duskside of the polar cap. The drift patterns in both the geographic inertial and the geomagnetic inertial frame were calculated taking into account the displacement between the geographic and geomagnetic poles. The displacement between the poles has an important effect on the plasma drift patterns. The results have important implications for both the interpretation of satellite data related to high-latitude ionospheric dynamics and the formation of ionospheric troughs }, keywords={ atmospheric composition atmospheric movements ionosphere magnetosphere ionospheric depletions geographic pole magnetospheric convection geomagnetic pole plasma drift patterns ionospheric dynamics ionospheric troughs high latitude plasma convection }, mynotes={UNREAD}, } @ARTICLE{SouthwoodNov78, author={Southwood, D.J. and Wolf, R.A.}, title={ An assessment of the role of precipitation in magnetospheric convection }, journal={Journal of Geophysical Research}, volume={83}, number={A11}, year={1978}, month={Nov}, pages={5227-32}, abstract={ Two ways are examined in which particle precipitation can affect the overall pattern of magnetospheric convection. First, loss due to precipitation may reduce the effectiveness of the shielding process that acts to prevent the high-latitude convection electric field from penetrating to low latitudes. Second, electron precipitation can strongly influence the flow pattern by modifying the ionospheric conductivity. It is concluded that shielding by the plasma sheet electron boundary is likely to be strongly dependent on the loss rate, but at the inner edge of the proton ring current it will always have some importance. It is also found that the combined effect of shielding and enhanced conductivity in the auroral zone can be rapid flow in the ionospheric trough, similar to recent observations }, keywords={ atmospheric electricity atmospheric electron precipitation atmospheric movements convection ionosphere magnetosphere magnetospheric convection particle precipitation ionospheric conductivity plasma sheet electron boundary loss rate proton ring current auroral zone rapid flow ionospheric trough atmospheric electron precipitation high latitude convection electric field shielding low latitude magnetosphere electrical conductivity enhancement }, mynotes={UNREAD}, } @ARTICLE{SchunkJul76, author={Schunk, R.W. and Banks, P.M. and Raitt, W.J.}, title={ Effects of electric fields and other processes upon the nighttime high-latitude F layer }, journal={Journal of Geophysical Research}, volume={81}, number={19}, year={1976}, month={Jul}, pages={3271-82}, abstract={ The authors have studied the dynamics of the nighttime high-latitude F-region with special emphasis on the formation of the electron density trough region which lies equatorward of the auroral oval. It is found that the absence of photoionisation together with ordinary ionic recombination and slow plasma convection velocity can give a deep trough over a period of many hours. However, the normal global pattern of electric fields has regions of plasma convection sufficiently rapid to affect the rate of O/sup +/-N/sub 2/ reactions and to speed the rate of ionospheric delay. In addition, the escape of thermal plasma via the polar wind as well as N/sub 2/ vibrational excitation and enhanced N/sub 2/ densities act to deplete the ionosphere. In combination these destructive processes can readily account for the great variety of troughs found by experimentation. Thus it appears that there is no single cause for the observed troughs but that at various times, different processes act together to create density depressions of substantial magnitude }, keywords={ atmospheric electricity electron density F-region electric fields electron density trough region nighttime high latitude F-region }, mynotes={UNREAD}, } @ARTICLE{MaynardMar75, author={Maynard, N.C. and Chen, A.J.}, title={ Isolated cold plasma regions: observations and their relation to possible production mechanisms }, journal={Journal of Geophysical Research}, volume={80}, number={7}, year={1975}, month={Mar}, pages={1009-13}, abstract={ Regions of enhanced cold plasma, isolated from the main plasmasphere along the Explorer 45(S/sup 3/-A) orbit in the equatorial plane, have been detected by using the sheath-induced potentials seen by the electric field experiment. The occurrence of these regions has a strong correlation with negative enhancements of Dst, and their locations are primarily in the noon-dusk quadrant. The data support the concept that changes in large-scale convection play a dominant role in the formation of these regions. Plasma tails that are predicted from enhancements of large-scale convection electric fields in general define where these regions may be found. More localized processes are necessary to account for the exact configuration and structure seen in these regions and may eventually result in detachment from the main plasmasphere }, keywords={ magnetosphere plasma isolated cold plasma regions production mechanisms negative enhancements electric field Dst plasma tails }, mynotes={UNREAD}, } @ARTICLE{CoronitiJun73, author={Coroniti, F.V. and Kennel, C.F.}, title={ Can the ionosphere regulate magnetospheric convection? }, journal={Journal of Geophysical Research}, volume={78}, number={16}, year={1973}, month={Jun}, pages={2837-51}, abstract={ Following a southward shift of the interplanetary magnetic field, which implies enhanced reconnection at the nose of the magnetosphere, the magnetopause shrinks from its Chapman-Ferraro equilibrium position. If the convective return of magnetic flux to the magnetopause equalled the reconnection rate, the magnetopause would not shrink. Consequently, there is a delay in the development of magnetospheric convection following the onset of reconnection, which is ascribed to line tying by the polar cusp ionosphere. A simple model relates the dayside magnetopause displacement to the currents feeding the polar cap ionosphere, from which the ionospheric electric field, and consequently the flux return rate, may be estimated as a function of magnetopause displacement. Flux conservation arguments then permit an estimate of the time scale on which convection increases, which is not inconsistent with that of the substorm growth phase }, keywords={ ionosphere magnetosphere magnetospheric convection interplanetary magnetic field magnetopause magnetic flux reconnection rate polar cusp ionosphere ionospheric electric field flux return rate substorm growth phase }, mynotes={UNREAD}, } @ARTICLE{SharberApr72, author={Sharber, J.R. and Heikkila, W.J.}, title={ Adiabatic processes in magnetospheric substorms }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={53}, number={4}, year={1972}, month={Apr}, pages={493}, abstract={ While the motion of moving magnetic field lines during substorms can be a useful concept, many aspects of magnetospheric substorm process can perhaps be better understood by considering the motion of charged particles in stationary crossed electric and magnetic fields. Simple considerations show that the geometry of the magnetotail is of vital importance, as is the presence of a dawn to dusk electric field. Adiabatic motion with conservation of the first and second invariants leads to ring currents and auroral particle energization respectively. The expansive phase starts when the beta of the trapped plasma in the tail approaches unity, permitting the magnetosheath plasma to push in on the dawn and dusk sides. That results in an increase in the local electric field intensity, and a speedup in the particle drift motions. Enhanced electron precipitation constitutes a field aligned current and produces a northward magnetic field which causes the poleward expansion of the aurora. The westward surge is also partly the result of this new magnetic field, but may also be affected by a change in the electric field pattern. During the recovery phase, the plasma sheet in the tail is replenished by convection from the dawn and dusk sides }, keywords={ aurora magnetic storms magnetosphere adiabatic processes magnetospheric substorms motion of charged particles stationary crossed electric and magnetic fields geometry magnetotail ring currents auroral particle energization magnetosheath plasma local electric field intensity particle drift motions enhanced electron precipitation field aligned current northward magnetic field poleward expansion westward surge aurora }, mynotes={UNREAD}, } @ARTICLE{CarpenterJun72, author={Carpenter, D.L. and Stone, K. and Siren, J.C. and Crystal, T.L.}, title={ Magnetospheric electric fields deduced from drifting whistler paths }, journal={Journal of Geophysical Research}, volume={77}, number={16}, year={1972}, month={Jun}, pages={2819-34}, abstract={ The amplitude of the E-W component E/sub w/ of the convection electric field in the nightside magnetosphere has been inferred from the observed cross-L motions of whistler ducts within the plasmasphere. Several ducts distributed over 1-2 R/sub E/ in L space and over +or-15 degrees around the longitude of the Eights, Antarctica, whistler station have been tracked simultaneously. The method appears capable of resolving fluctuations in E/sub w/ with period T approximately 15 min and rms amplitude as low as 0.05 mv/m. For variations with T>1 hour the method has a sensitivity of the order of 0.01 mv/m. Three case studies are presented, two of which illustrate convection activity associated with relatively isolated substorms. In these two cases E/sub w/ reversed from westward to eastward for a period following the decay of substorm bay activity. In the third case the substorm bay activity was prolonged, and E/sub w/ remained westward and at enhanced levels until local dawn }, keywords={ atmospheric electricity atmospherics magnetosphere magnetospheric electric fields drifting whistler paths nightside magnetosphere plasmasphere }, mynotes={UNREAD}, } @ARTICLE{BurkeNov70, author={Burke, W.J. and Vasyliunas, V.M.}, title={ A model of auroral arcs and auroral particle acceleration }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={51}, number={11}, year={1970}, month={Nov}, pages={809}, abstract={ The assumption of strong pitch angle diffusion within the plasma sheet predicts an approximately uniform electron precipitation over the auroral oval. To explain the occurrence of individual auroral arcs, the authors postulate that the return currents associated with the uniform precipitation maintain large parallel electric fields, through anomalous resistivity. They show that magnetospheric convection leads to strong localized electron acceleration where there are horizontal gradients in the parallel electric field. The model predicts, in agreement with observations, (a) long thin regions of enhanced precipitation, aligned with the auroral oval, (b) an electron energy spectrum with a sharp peak superimposed on a continuous background (c) a field-aligned current carried by precipitating electrons within the arc, with a return current outside of the arc }, keywords={ aurora upper atmosphere aurora arcs particle acceleration model pitch angle diffusion electron precipitation magnetospheric convection }, mynotes={UNREAD}, } @ARTICLE{FarrugiaMay93, author={Farrugia, C.J. and Freeman, M.P. and Burlaga, L.F. and Lepping, R.P. and Takahashi, K.}, title={ The Earth's magnetosphere under continued forcing: substorm activity during the passage of an interplanetary magnetic cloud }, journal={Journal of Geophysical Research}, volume={98}, number={A5}, year={1993}, month={May}, pages={7657-71}, abstract={ Substorm activity attending the 30-hour-long passage of the magnetic cloud seen at 1 AU on January 14/15, 1988 is studied. The authors main aim is to describe high resolution field and plasma data from six spacecraft at geostationary orbit and beyond (up to 9 R/sub E/), supplemented by ground magnetograms, in order to estimate the number of substorm onsets that occurred during this passage. This analysis, attempted for the first time over such an extended data interval, enables the authors to obtain a comprehensive view of the magnetospheric behavior. They then relate the interplanetary field and plasma input to the magnetospheric and ionospheric output. The paper is a case study of the response of the nightside magnetosphere to particularly well-behaved interplanetary conditions }, keywords={ magnetic storms magnetosphere solar wind magnetic storm solar wind magnetosphere interaction Earth AD 1988 01 IMF electric field interplanetary magnetic field continued forcing substorm activity interplanetary magnetic cloud plasma onsets nightside }, mynotes={UNREAD}, } @ARTICLE{FarrugiaMay93, author={Farrugia, C.J. and Burlaga, L.F. and Osherovich, V.A. and Richardson, I.G. and Freeman, M.P. and Lepping, R.P. and Lazarus, A.J.}, title={ A study of an expanding interplanetary magnetic cloud and its interaction with the Earth's magnetosphere: the interplanetary aspect }, journal={Journal of Geophysical Research}, volume={98}, number={A5}, year={1993}, month={May}, pages={7621-32}, abstract={ The authors present a study of a interplanetary magnetic cloud and its interaction with the Earth's magnetosphere on January 14/15, 1988. The principal results concerning the magnetic cloud are described. First, by applying the cylindrically symmetric, magnetic flux rope model to the high time resolution magnetic field and plasma data obtained by the IMP-8 spacecraft, it is shown that the axis of the magnetic cloud in question is approximately in the ecliptic and orthogonal to the Earth-Sun line. The authors note the presence of pulsations of approximately 5-hour period in the bulk flow speed which are superimposed on an otherwise monotonically falling bulk speed profile. Second, they apply an ideal MHD to model the self-similar, radial expansion of a magnetic cloud of cylindrical geometry. The theoretical velocity profile for the free expansion of a magnetic cloud is consistent with observations made during the January 14/15, 1988, magnetic cloud encounter }, keywords={ interplanetary magnetic fields magnetosphere solar wind Earth solar wind magnetosphere interaction IMF interplanetary magnetic field AD 1988 01 15 AD 1988 01 14 expanding interplanetary magnetic cloud cylindrically symmetric magnetic flux rope model ideal MHD free expansion }, mynotes={UNREAD}, } @ARTICLE{FreemanDec95, author={Freeman, M.P. and Farrugia, C.J.}, title={ A statistical study of the possible effects of solar wind variability on the recurrence rate of substorms }, journal={Journal of Geophysical Research}, volume={100}, number={A12}, year={1995}, month={Dec}, pages={23607-19}, abstract={ The recurrence of substorms in the terrestrial magnetosphere depends on many factors. Chief among these are (1) the mechanism(s) by which the magnetosphere stores and rids itself of excess magnetic flux accumulated in the tail (loading-unloading behavior) and (2) the way in which the power input from the solar wind to the magnetosphere (the coupling) varies with time. The authors explore the possible effects of the variability of the interplanetary medium on the statistical temporal distribution of substorms, using a simple substorm model. In this model, substorms recur at fixed time intervals in response to a steady solar wind power input, regardless of its level. In their simulations the power input into the magnetosphere is measured by the rectified north-south component, B/sub s/, of the interplanetary magnetic field (IMF). The authors use IMF data at 15-s resolution from long-term surveys to construct three statistical model inputs: (1) the random B/sub s/ model, (2) the shortwave B/sub s/ model, and (3) the longwave B/sub s/ model. They find that all the resultant distributions of intersubstorm intervals are skewed with respect to a clear modal peak and cover a wide range of intersubstorm intervals. They also find that the temporal succession of substorm onsets is sensitive to the ratio of the timescale of IMF variation to the assumed intrinsic intersubstorm period. For small values of this ratio the mode of the distribution can be greater than the intrinsic intersubstorm interval by a factor of 2 or more. For large values of this ratio the modal substorm recurrence rate approaches the intrinsic value. They also assess the effect on the temporal distribution of substorm onsets of random (failure to identify a substorm onset) and quasi-random (incomplete coverage) errors. they use their findings to interpret the results of a large-scale survey of substorm recurrence rates in the terrestial magnetosphere under nonstorm conditions recently undertaken }, keywords={ magnetic storms solar wind solar wind magnetosphere interaction statistical study solar wind variability recurrence rate substorm magnetic storm mechanism loading-unloading behavior coupling temporal distribution model interplanetary magnetic field onset IMF }, mynotes={UNREAD}, } @ARTICLE{BargatzeJul85, author={Bargatze, L.F. and Baker, D.N. and McPherron, R.L. and Hones, E.W., Jr.}, title={ Magnetospheric impulse response for many levels of geomagnetic activity }, journal={Journal of Geophysical Research}, volume={90}, number={A7}, year={1985}, month={Jul}, pages={6387-94}, abstract={ The temporal relationship between the solar wind and magnetospheric activity has been studied using 34 intervals of high time resolution IMP 8 solar wind data and the corresponding AL auroral activity index. The median values of the AL index for each interval were utilized to rank the intervals according to geomagnetic activity level. The linear prediction filtering technique was then applied to model magnetospheric response as measured by the AL index to the solar wind input function VB/sub s/. It is found that the filters are composed of two response pulses speaking at time lags of 20 and 60 min. The amplitude of the 60-min pulse is the larger for moderate activity levels, while the 20-min pulse is the larger for strong activity levels. A possible interpretation is that the 20-min pulse represents magnetospheric activity driven directly by solar wind coupling and that the 60-min pulse represents magnetospheric activity driven by the release of energy previously stored in the magnetotail }, keywords={ magnetosphere magnetosphere impulse response geomagnetic activity solar wind magnetospheric activity A L auroral activity index }, mynotes={UNREAD}, } @ARTICLE{BakerFeb85, author={Baker, D.N. and Fritz, T.A. and Lennartsson, W. and Wilken, B. and Kroehl, H.W. and Birn, J.}, title={ The role of heavy ionospheric ions in the localization of substorm disturbances on March 22, 1979: CDAW 6 }, journal={Journal of Geophysical Research}, volume={90}, number={A2}, year={1985}, month={Feb}, pages={1273-81}, abstract={ Extensive ground-based arrays of magnetometers and numerous satellite platforms in the outer magnetosphere have established that two separate substorm expansion onsets occurred on March 22, 1979. The first of these occurred at 1055 UT and is demonstrated to be localized in the 0200-0300 LT sector. Concurrent plasma sheet ion composition measurements are used to show that the growth and expansion phase of the substorm occurred while the outer magnetosphere was composed dominantly of solar wind (H/sup +/ and He/sup ++/) plasmas. The 1055 UT substorm greatly perturbed and altered the ion composition of the plasma in the outer magnetosphere such that the second substorm expansion onset (1436 UT) occurred while the outer magnetospheric plasmas were dominantly of ionospheric (O/sup +/) origin }, keywords={ magnetic storms heavy ions magnetosphere AD 1979 03 22 longitude O/sup +/ ionospheric ions localization substorm disturbances CDAW 6 substorm expansion onsets plasma sheet ion composition growth expansion phase outer magnetosphere }, mynotes={UNREAD}, } @ARTICLE{BakerFeb85, author={Baker, D.N. and Fritz, T.A. and McPherron, R.L. and Fairfield, D.H. and Kamide, Y. and Baumjohann, W.}, title={ Magnetotail energy storage and release during the CDAW 6 substorm analysis intervals }, journal={Journal of Geophysical Research}, volume={90}, number={A2}, year={1985}, month={Feb}, pages={1205-16}, abstract={ Using solar wind, magnetotail, and geostationary particle and field data, as well as ground-based information, the authors present evidence for enhanced solar wind-magnetosphere coupling and concomitant increases of stored magnetotail energy. Clear examples of energy storage are found prior to the 1055 and 1435 UT substorms of March 22, as well as the 0250 UT and 2250 UT substorms on April 1 and March 31, respectively. In these cases the total energy increase in the tail prior to the substorm onsets is estimated and the dissipation rate of this energy during the substorms themselves is estimated }, keywords={ magnetic storms magnetosphere energy release magnetotail magnetosphere magnetic storm AD 1979 03 22 AD 1979 04 01 AD 1979 03 31 energy storage CDAW 6 substorm analysis intervals solar wind-magnetosphere coupling }, mynotes={UNREAD}, } @ARTICLE{BakerFeb85, author={Baker, K.B. and Kamide, Y.}, title={ A comparison of ionospheric electric fields inferred from Scandinavian Twin Auroral Radar Experiment drift data and from global International Magnetospheric Study magnetometer data }, journal={Journal of Geophysical Research}, volume={90}, number={A2}, year={1985}, month={Feb}, pages={1339-42}, abstract={ For the two Coordinated Data Analysis Workshop 6 periods, March 22 and March 31 to April 1, 1979, Kamide et al. have used global International Magnetospheric Study (IMS) magnetometer data along with the Rice ionospheric conductivity model to estimate the electric fields and currents at high latitudes. This procedure can be checked by comparing these results with the electric fields inferred from the drift velocities measured by the Scandinavian Twin Auroral Radar Experiment radars. It was found that, in general, the two methods agree to within 20%, confirming the utility of the IMS magnetometer data in estimating the global electric field distribution }, keywords={ ionosphere ionospheric techniques plasma drift STARE IMS AD 1979 03 22 AD 1979 03 31 AD 1979 04 01 measurement technique radar method ionospheric electric fields Scandinavian Twin Auroral Radar Experiment International Magnetospheric Study magnetometer data Rice ionospheric conductivity model drift velocities }, mynotes={UNREAD}, } @ARTICLE{ChenJul95, author={Chen, J. and Slinker, S. and Fedder, J.A. and Lyon, J.G.}, title={ Simulation of geomagnetic storms during the passage of magnetic clouds }, journal={Geophysical Research Letters}, volume={22}, number={13}, year={1995}, month={Jul}, pages={1749-52}, abstract={ The response of the Earth's magnetosphere to the passage of interplanetary magnetic clouds is simulated using a three-dimensional magnetohydrodynamic (MHD) model. The input solar wind condition is given by the magnetic field, particle density, and plasma flow calculated from a model magnetic cloud. The cross-polar potential ( Phi /sub p/), Joule heating and electron energy precipitation into the polar cap are calculated. Synthetic magnetic indices D/sub st/* and AE* are defined to serve as surrogates for the usual D/sub st/ and AE indices, respectively. The authors demonstrate that Phi /sub p//sup 2/ provides a good predictor of the energy deposition into the ionosphere during storm conditions and that D/sub st/* and AE* behave qualitatively similarly to D/sub st/ and AE }, keywords={ interplanetary magnetic fields ionosphere magnetic storms magnetosphere geomagnetic storm simulation interplanetary magnetic cloud passage Earth magnetosphere response 3D MHD model solar wind condition magnetic field particle density plasma flow cross-polar potential Joule heating electron precipitation polar cap synthetic magnetic indices energy deposition ionosphere magnetic storm conditions }, mynotes={UNREAD}, } @ARTICLE{FedderOct95, author={Fedder, J.A. and Slinker, S.P. and Lyon, J.G. and Elphinstone, R.D.}, title={ Global numerical simulation of the growth phase and the expansion onset for a substorm observed by Viking }, journal={Journal of Geophysical Research}, volume={100}, number={A10}, year={1995}, month={Oct}, pages={19083-93}, abstract={ Reports the first global magnetohydrodynamic (MHD) simulation of an actual magnetospheric substorm, which was recorded by the Viking spacecraft on October 19, 1986. The simulation is driven by IMP 8 solar wind parameters measured upstream of the Earth's bow shock. The substorm, which had expansion onset at 1132 UT, was caused by a brief period of southward interplanetary magnetic field (IMF) and two weak solar wind shocks. The simulation model includes a self-consistent auroral ionospheric conductance depending directly on the MHD magnetospheric plasma parameters and magnetic field. Synthetic auroral emissions, derived from simulation results, are compared to the Viking images, which show considerable dayside activity preceding the substorm. The authors also compare model-derived synthetic AU and AL indices to geomagnetic measurements. The simulation results are seen to be in reasonable agreement with the observations throughout the growth phase and expansion onset. Moreover, the results allow one to form conclusions concerning which essential processes were responsible for the substorm occurrence. These results are a highly encouraging first step leading toward development of a space weather forecasting methodology based on the directly measured solar input }, keywords={ aurora magnetic storms plasma magnetohydrodynamics gobal numerical simulation growth phase expansion onset substorm magnetohydrodynamic simulation solar wind parameters southward interplanetary magnetic field solar wind shocks self-consistent auroral ionospheric conductance magnetic field auroral emissions dayside activity AU indices AL indices space weather forecasting methodolog AD 1986 10 19 }, mynotes={UNREAD}, } @ARTICLE{PerreaultSep78, author={Perreault, P. and Akasofu, S.-I.}, title={ A study of geomagnetic storms }, journal={Geophysical Journal of the Royal Astronomical Society}, volume={54}, number={3}, year={1978}, month={Sep}, pages={547-83}, abstract={ An attempt is made to find interplanetary magnetic field and solar wind parameters with control the development of geomagnetic storms. For this purpose the interplanetary energy flux is estimated in terms of the Poynting flux, and its time variations are compared with the rate of energy dissipation in terms of the ring-current particle injection. Joule dissipation in the ionosphere and auroral particle injection for 15 major geomagnetic storms. It is shown that the growth of geomagnetic storms, namely the time variations of the rate of the total energy dissipation, is closely related to the Poynting flux. The energy flux entering the magnetosphere is dissipated through magnetospheric substorm processes within the magnetosphere and their accumulated effects can be understood as geomagnetic storm phenomena }, keywords={ interplanetary magnetic fields magnetic storms solar wind geomagnetic storms interplanetary magnetic field interplanetary energy flux Poynting flux energy dissipation auroral particle injection magnetosphere substorm processes solar wind ring current }, mynotes={UNREAD}, } @ARTICLE{KozyraMar94, author={Kozyra, J.U. and Rasmussen, C.E. and Miller, R.H. and Lyons, L.R.}, title={ Interaction of ring current and radiation belt protons with ducted plasmaspheric hiss. 1. Diffusion coefficients and timescales }, journal={Journal of Geophysical Research}, volume={99}, number={A3}, year={1994}, month={Mar}, pages={4069-84}, abstract={ Protons that are convected into the inner magnetosphere in response to enhanced magnetic activity can resonate with ducted plasmaspheric hiss in the outer plasmasphere via an anomalous Doppler-shifted cyclotron resonance. Plasmaspheric hiss is a right-hand-polarized electromagnetic emission that is observed to fill the plasmasphere on a routine basis. When plasmaspheric hiss is confined within field-aligned ducts or guided along density gradients, wave normal angles remain largely below 45 degrees . This allows resonant interactions with ions at typical ring current and radiation belt energies to take place. Such field-aligned ducts have been observed both within the plasmasphere and in regions outside of the plasmasphere. Wave intensities are estimated using statistical information from studies of detached plasma regions (Chan et al. 1974). Diffusion coefficients are presented for a range of L shells and proton energies for a fixed wave distribution. Harmonic resonances in the range n=+or-100 are considered in order to include interactions between hiss at 100 Hz to 2 kHz frequencies, and protons in the energy range between approximately 10 keV and 1000 keV. Diffusion timescales are estimated to be of the order of tens of days and comparable to or shorter than lifetimes for Coulomb decay and charge exchange losses over most of the energy and spatial ranges of interest }, keywords={ magnetosphere radiation belts wave particle interaction inner magnetosphere ring current radiation belt proton ducted plasmaspheric hiss radiowave diffusion coefficient timescale resonate outer plasmasphere anomalous Doppler-shifted cyclotron resonance right-hand-polarized electromagnetic emission field-aligned duct resonant interaction }, mynotes={UNREAD}, } @ARTICLE{ChenMar92, author={Chen, M.W. and Schulz, M. and Lyons, L.R. and Gorney, D.J.}, title={ Ion radial diffusion in an electrostatic impulse model for stormtime ring current formation }, journal={Geophysical Research Letters}, volume={19}, number={6}, year={1992}, month={Mar}, pages={621-4}, abstract={ Guiding-center simulations of stormtime transport of ring-current and radiation-belt ions having first adiabatic invariants mu >or approximately= 15 MeV/G (E>or approximately=165 keV at L approximately 3) are surprisingly well described (typically within a factor of or approximately=40 keV particles into the storm time current ring can result from enhanced stochastic radial transport driven by fluctuating electric fields during a storm's main phase. The authors estimate the effects of such electric fields by applying radial-diffusion theory, assuming a preexisting trapped-particle population as the initial condition, and demonstrate the feasibility of explaining observed flux increases of >or approximately=40-keV particles at L6 region, 47% are associated with EMIC wave onset at the satellite. Compression energize particles via earthward convection, so the association of local Pc 1 onsets with compressions may be either a temporal effect or merely the result of inward transport to the spacecraft of plasma previously unstable to EMIC waves }, keywords={ micropulsations plasma waves stimulation outer magnetosphere compression plasma wave EM ion cyclotron wave micropulsation magnetic pulsation sudden impulses enhancements onset Pc 1 hot proton temperature anisotropy convection dayside equatorial EMIC }, mynotes={UNREAD}, } @ARTICLE{StudemannSep86, author={Studemann, W. and Wilken, B. and Baker, D.N. and Higbie, P.R. and Belian, R.D. and Fritz, T.A.}, title={ Multispacecraft observations at the compressed magnetopause following the 13 July 1982 interplanetary shock }, journal={Planetary and Space Science}, volume={34}, number={9}, year={1986}, month={Sep}, pages={825-33}, abstract={ The global magnetospheric compression on 13 July 1982 following the arrival of an interplanetary shock was observed by a number of spacecraft. Energetic electron and ion data as well as magnetometer measurements on three geostationary spacecraft operating on the frontside of the magnetosphere are used to obtain information about the shape of the magnetopause during times of enhanced solar wind dynamic pressure. The deviation from the average shape of the uncompressed magnetopause to a more circular shape found occasionally during the event is discussed. Unidirectional distributions of energetic (up to approximately 300 keV) ions found at the magnetopause outside the last closed field line for a period of more than 1 h are interpreted }, keywords={ magnetosphere shock waves solar wind atmosphere AD 1982 07 13 magnetopause 13 July 1982 interplanetary shock magnetospheric compression electron ion data magnetometer measurements enhanced solar wind dynamic pressure field line }, mynotes={UNREAD}, } @ARTICLE{ShelleyMay85, author={Shelley, E.G. and Klumpar, D.M. and Peterson, W.K. and Ghielmetti, A. and Balsiger, H. and Geiss, J. and Rosenbauer, H.}, title={ AMPTE/CCE observations of the plasma composition below 17 keV during the September 4, 1984 magnetic storm }, journal={Geophysical Research Letters}, volume={12}, number={5}, year={1985}, month={May}, pages={321-4}, abstract={ Observations from the Hot Plasma Composition Experiment on the AMPTE/CCE spacecraft during the magnetic storm of 4-5 September 1984 reveal that significant injection of ions of terrestrial origin accompanied the storm development. The compression of the magnetosphere at storm sudden commencement carried the magnetopause inside the CCE orbit clearly revealing the shocked solar wind plasma. A build up of suprathermal ions is observed near the plasmapause during the storm main phase and recovery phase. Pitch angle distributions in the ring current during the main phase show differences between H/sup +/ and O/sup +/ that suggest mass dependent injection, transport and/or loss processes }, keywords={ magnetic storms magnetosphere trapped particle AD 1984 09 04 plasma composition magnetic storm ions terrestrial origin storm development compression sudden commencement magnetopause suprathermal ions ring current }, mynotes={UNREAD}, } @ARTICLE{AlfsenOct84, author={Alfsen, K.H. and Bonifazi, C. and Pedersen, A. and Lindqvist, P.-A.}, title={ Interaction between an interplanetary shock and the Earth's magnetosphere on August 27, 1978: ISEE 1 electric field and ISEE 2 plasma observations }, journal={Journal of Geophysical Research}, volume={89}, number={A10}, year={1984}, month={Oct}, pages={8863-71}, abstract={ An interplanetary shock caused a rapid compression of the magnetosphere on August 27, 1978. The ISEE 1/ISEE 2 pair of satellites were in the frontside magnetosphere before the shock, and subsequently a magnetosonic wave front, the magnetopause, and the bow shock passed the ISEE satellites in a very short time. Previous papers determined boundary velocities from magnetic time delay measurements. These papers form a starting point for the study of electric field data during these events. By a combination of electric and magnetic field data it is possible to determine both the magnetosonic velocity and the magnetopause velocity. Furthermore, it is possible to establish with good confidence that during this compressional motion the E*B velocity was toward the magnetopause from both sides }, keywords={ atmospheric electricity atmospheric movements magnetosphere plasma shock waves solar wind solar wind atmospheric movement AD 1978 08 27 interplanetary shock magnetosphere ISEE 1 ISEE 2 compression August 27, 1978 magnetosonic wave front bow shock boundary velocities magnetic time delay electric field }, mynotes={UNREAD}, } @ARTICLE{KokubunDec83, title={ Characteristics of storm sudden commencement at geostationary orbit }, journal={Journal of Geophysical Research}, volume={88}, number={A12}, year={1983}, month={Dec}, pages={10025-33}, abstract={ Eighty-one storm sudden commencements (SSC) observed on board GOES satellites at geostationary orbit are used to examine the local time variation of SSC amplitude. It is found that SSC amplitudes at synchronous altitude have a strong local time dependence in contrast to previous observations in the magnetosphere. Amplitude ratios (satellite amplitude/ground amplitude) are larger than unity in most cases observed in the daytime during 0600-1500 LT. The SSC amplitude tends to become very small near midnight as compared with that on the ground. Even a decrease in total force sometimes occurs in the midnight region. This means that magnetic compression does not always occur in the magnetic equator near synchronous orbit. The implication of these SSC characteristics are discussed in relation to SSC-associated phenomena }, keywords={ magnetic storms magnetosphere SCC magnetic storm storm sudden commencement geostationary local time variation SSC amplitude local time dependence magnetosphere magnetic compression }, mynotes={UNREAD}, } @ARTICLE{WolfAug82, author={Wolf, R.A. and Harel, M. and Spiro, R.W. and Voigt, G.-H. and Reiff, P.H. and Chen, C.-K.}, title={ Computer simulation of inner magnetospheric dynamics for the magnetic storm of July 29, 1977 }, journal={Journal of Geophysical Research}, volume={87}, number={A8}, year={1982}, month={Aug}, pages={5949-62}, abstract={ Presents preliminary results of applying the Rice convection model to the early main phase of the magnetic storm of July 29, 1977. The computer model self-consistently computes electric fields and currents, as well as plasma distributions and velocities, in the inner-magnetosphere/ionosphere system. In the equatorial plane, the region modeled includes geocentric distances less than about the magneto-pause standoff distance. On the basis of solar wind parameters and the AL index as input, the model predicts the injection of plasma-sheet plasma to form a substantial storm time ring current. Birkeland currents are also calculated. The authors examine the possibility that the magnetic field might be so highly inflated that 60 degrees field lines might extend to the outer magnetosphere. In the model, distortion of the inner edge of the plasma sheet by magnetospheric compression associated with sudden commencement temporarily disturbs the normal Birkeland-current pattern. The normal tendency for the plasma sheet's inner edge to shield low L values from the convection electric field is also temporarily disrupted }, keywords={ ionosphere magnetic storms magnetosphere inner magnetosphere AD 1977 07 29 electric current ionosphere plasma motion Birkeland configuration dynamics magnetic storm Rice convection model early main phase electric fields injection plasma-sheet ring current }, mynotes={UNREAD}, } @ARTICLE{SaitoJun74, author={Saito, T. and Takahashi, F. and Morioka, A. and Kuwashima, M.}, title={ Fluctuations of electron precipitation to the dayside auroral zone modulated by compression and expansion of the magnetosphere }, journal={Planetary and Space Science}, volume={22}, number={6}, year={1974}, month={Jun}, pages={939-53}, abstract={ Concurrent variations of CNA fluctuations and geomagnetic fluctuations are classified into Type 1 (substorm-type), Type 2 (Pc5-type), and Type 3 which is the object of the present study. Type 3 apparently has peculiar characteristics in that CNA fluctuations at a certain auroral-zone station show a pronounced positive correlation with magnetic fluctuations at distant low-latitude stations. Considering the change of the growth rate of electron cyclotron instability and enhancement of pitch angle diffusion due to the change of magnetic field intensity, the following model is proposed to explain the occurrence mechanism of Type 3 concurrent variations. The CNA fluctuations take place only when two conditions are satisfied; generation of the accelerated electrons in association with substorm onset and modulation of the precipitation of the electrons by compression and expansion of the magnetosphere, in other words, by generalized Si }, keywords={ atmospheric electron precipitation geomagnetic variations magnetosphere electron precipitation dayside auroral zone compression expansion magnetosphere Type 3 generalized Si cosmic noise absorption geomagnetic variations }, mynotes={UNREAD}, } @ARTICLE{NeugebauerNov70, author={Neugebauer, M. and Russell, C.T. and Chappell, C.R.}, title={ OGO-5 observations during the geomagnetic storm of November 1, 1968 }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={51}, number={11}, year={1970}, month={Nov}, pages={811}, abstract={ The period from October 26 to November 6, 1968 was the most geomagnetically active period during 1968. DST reached a minimum of -211 gammas; Kp reached a maximum of 8+; and SAR arcs were observed. OGO-5 made several magnetospheric passes during this interval. On one of these passes, on Nov. 1, OGO-5 was outbound, about 45 degrees magnetic latitude, in the dayside magnetosphere, and observed several unusual features. The magnetic field was severely distorted and the low frequency (.1-10 hz) wave amplitude was high (up to 20 gammas). Outside the stable trapping boundary large fluxes of low energy electrons were often encountered with average energies about 300-400 eV and densities as high as 40/cm/sup 3/. The magnetopause was encountered at 7.2 Re at a SES angle of 61.4 degrees . Extrapolating this position to the subsolar point assuming a uniform compression of the magnetopause gives a distance of 6.25 Re for the stagnation point }, keywords={ magnetic storms magnetosphere upper atmosphere geomagnetic storm OGO-5 observations magnetosphere magnetic field distortion }, mynotes={UNREAD}, } @ARTICLE{MorrisonApr94, author={Morrison, K. and Engebretson, M.J. and Beck, J.R. and Johnson, J.E. and Arnoldy, R.L. and Cahill, L.J. and Jr., Carpenter and D.L. and Gallani, M.}, title={ A study of quasi-periodic ELF-VLF emissions at three Antarctic stations: evidence for off-equatorial generation2Q }, journal={Annales Geophysicae}, volume={12}, number={2-3}, year={1994}, month={Apr}, pages={139-46}, abstract={ The spatial extent and temporal behaviour of quasi-periodic (QP) intensity modulations of 0.5-2 kHz ELF-VLF signals were investigated in a comparative study of data collected at the Antarctic stations of South Pole (L=14), Halley (L=4), and Siple (L=4). Frequently, the waveforms of ELF-VLF signals received simultaneously at each site were identical. Although of similar frequency structure, the waveforms of the accompanying Pc3 magnetic pulsations did not show a one-to-one association. Whereas both are dayside phenomena, QP emissions occur over a smaller range of local times, and have a maximum of occurrence later in the day closer to local noon. QP emissions are identified with the periodic modulation of the electron pitch-angle distribution by the propagation of ULF compressional fast-mode waves through a region. The authors propose an additional high-latitude source of QP emissions. These emissions are associated with regions of minimun B produced by the dayside compression of the magnetosphere close to the magnetopause }, keywords={ atmospheric radiation atmospherics magnetosphere plasma waves magnetosphere EH wave emissions AD 1986 09 dayside outer magnetosphere compression minimum magnetic field regions rising tone emissions ELF-VLF signals local time distribution ELF-VLF signals waveforms magnetosphere MHD waves electron cyclotron resonance modulation ELF-VLF signals intensity modulation quasi-periodic ELF-VLF emissions Antarctic stations off-equatorial generation South Pole Halley Siple frequency structure Pc3 magnetic pulsations dayside phenomena periodic modulation electron pitch-angle distribution ULF compressional fast-mode waves high-latitude source QP emissions magnetopause 0.5 to 2 kHz }, mynotes={UNREAD}, } @ARTICLE{Lyatskiy87, author={Lyatskiy, V.B. and Safargaleyev, V.V.}, title={ Transformation of a magnetoacoustic wave into an Alfven wave during SC and SI }, journal={Geomagnetizm i Aeronomiya}, volume={27}, number={2}, year={1987}, month={}, pages={}, abstract={ The generation mechanism of toroidal Alfven oscillations during the compression or expansion of the magnetosphere is investigated. The initial magnetoacoustic pulse transforms into an Alfven wave as a result of a disturbance of the azimuthal motion (convection) of the magnetospheric plasma. A comparison of the computed and observed amplitudes of disturbances generated testifies to a fairly high efficiency of the proposed mechanism }, keywords={ magnetic storms magnetosphere magnetic storm sudden commencement sudden impulse plasma wave transformation magnetoacoustic wave Alfven wave SC SI generation mechanism toroidal Alfven oscillations compression expansion magnetosphere initial magnetoacoustic pulse transforms disturbance magnetospheric plasma }, mynotes={UNREAD}, } @ARTICLE{BaumjohannNov83, author={Baumjohann, W. and Bauer, O.H. and Haerendel, G. and Junginger, H. and Amata, E.}, title={ Magnetospheric plasma drifts during a sudden impulse }, journal={Journal of Geophysical Research}, volume={88}, number={A11}, year={1983}, month={Nov}, pages={9287-9}, abstract={ An interplanetary shock front hit the Earth's magnetosphere on October 17, 1978, around 0430 UT. The changes in magnetospheric plasma drift and magnetic field associated with this sudden impulse (SI) were measured by GEOS 2 in the equatorial plane near the dawn meridian. After the SI the plasma drift first increased (in an inward direction), followed by an exponential decay. The magnetic field changes were purely compressional with an amplitude increase which also exponentially decayed. These features can be explained by adiabatic (quasi-static) compression of the magnetopause due to the increased solar wind pressure behind the shock front. In addition, both data sets exhibit also the excitation of a highly damped compressional hydromagnetic oscillation by the SI, thus hinting of a second, wavelike component in the compression of the magnetosphere }, keywords={ magnetosphere solar wind AD 1978 10 17 solar wind interaction motion disturbed micropulsation plasma drifts sudden impulse interplanetary shock front magnetosphere magnetic field changes magnetopause solar wind highly damped compressional hydromagnetic oscillation }, mynotes={UNREAD}, } @ARTICLE{WolfAug82, author={Wolf, R.A. and Harel, M. and Spiro, R.W. and Voigt, G.-H. and Reiff, P.H. and Chen, C.-K.}, title={ Computer simulation of inner magnetospheric dynamics for the magnetic storm of July 29, 1977 }, journal={Journal of Geophysical Research}, volume={87}, number={A8}, year={1982}, month={Aug}, pages={5949-62}, abstract={ Presents preliminary results of applying the Rice convection model to the early main phase of the magnetic storm of July 29, 1977. The computer model self-consistently computes electric fields and currents, as well as plasma distributions and velocities, in the inner-magnetosphere/ionosphere system. In the equatorial plane, the region modeled includes geocentric distances less than about the magneto-pause standoff distance. On the basis of solar wind parameters and the AL index as input, the model predicts the injection of plasma-sheet plasma to form a substantial storm time ring current. Birkeland currents are also calculated. The authors examine the possibility that the magnetic field might be so highly inflated that 60 degrees field lines might extend to the outer magnetosphere. In the model, distortion of the inner edge of the plasma sheet by magnetospheric compression associated with sudden commencement temporarily disturbs the normal Birkeland-current pattern. The normal tendency for the plasma sheet's inner edge to shield low L values from the convection electric field is also temporarily disrupted }, keywords={ ionosphere magnetic storms magnetosphere inner magnetosphere AD 1977 07 29 electric current ionosphere plasma motion Birkeland configuration dynamics magnetic storm Rice convection model early main phase electric fields injection plasma-sheet ring current }, mynotes={UNREAD}, } @ARTICLE{KnippFeb96, author={Knipp, D.J. and Emery, B.A.}, title={ Polar cap contraction associated with the leading edge of a magnetic cloud }, journal={Geophysical Research Letters}, volume={23}, number={3}, year={1996}, month={Feb}, pages={305-16}, abstract={ In the early hours of 14 January 1988 a large magnetic cloud passed the Earth. The authors show evidence of a sudden impulse associated with the leading edge of the main body of the magnetic cloud and map the evolution of the convection patterns which are indicative of polar cap contraction associated with the subsequent, large, northward-directed interplanetary magnetic field. The authors provide a unique, step-by-step view of the high latitude events, simultaneously tracing both dayside and nightside responses to the solar wind variations. The maps provide clear global-scale support for polar cap expansion/contraction theory. The final state of convection in the northern hemisphere was one of extreme quiescence with the suspension of both dayside and nightside reconnection and a near total loss of motional electric fields mapping into the ionosphere. The authors discuss how this state developed }, keywords={ interplanetary magnetic fields ionospheric disturbances AD 1988 01 14 polar cap contraction magnetic cloud leading edge sudden impulse convection pattern evolution northward-directed interplanetary magnetic field high latitude events solar wind variations dayside response nightside response polar cap expansion theory quiescence reconnection electric fields ionosphere }, mynotes={UNREAD}, } @ARTICLE{SastriOct93, author={Sastri, J.H. and Visweswara Rao, J.V.S. and Ramesh, K.B.}, title={ Penetration of polar electric fields to the nightside dip equator at times of geomagnetic sudden commencements }, journal={Journal of Geophysical Research}, volume={98}, number={A10}, year={1993}, month={Oct}, pages={17517-23}, abstract={ Measurements of Doppler Velocity, V/sub D/ of F-region reflections at normal incidence over Kodaikanal (dip 3 degrees N, 77 degrees 28'E) are used to study the nature of perturbations in F-region vertical plasma drift, V/sub z/ associated with the geomagnetic sudden commencements (sc) on July 8, 1991, and January 1, 1992. Both the events which occurred in a narrow time window, 1630-1700 UT were of sc* type at middle and high latitude stations in the afternoon sector. At Kodaikanal, which is on the nightside, the sc of January 1, 1992, is characterized by a double-step main impulse (MI) in H component. It is found that the usual downward motion of F-region plasma during the premidnight hours at Kodaikanal suddenly ceased (and even reversed to upward in one event) for approximately 1 min coincident with the preliminary impulse (PI) and was immediately enhanced in association with the MI of the sc*. This pattern implies that an eastward electric field prevails near the nightside dip equator at the time of the first impulse of double-step MI there and the PI of sc* at high latitudes. These Doppler velocity observations constitute the first and direct experimental evidence of vertical plasma motions due to the sc-associated electric fields in the nighttime dip equatorial ionosphere }, keywords={ F-region ionosphere polar electric field penetration nightside dip equator sudden commencement magnetic storm F-region Kodaikanal vertical plasma drift AD 1991 07 08 AD 1992 01 01 preliminary impulse ionosphere disturbance plasma flow }, mynotes={UNREAD}, } @ARTICLE{LeonovichApr91, author={Leonovich, A.S. and Mazur, V.A.}, title={ An electromagnetic field, induced on the Earth's surface by standing Alfven waves in the magnetosphere: the particular kinds of oscillations }, journal={Planetary and Space Science}, volume={39}, number={4}, year={1991}, month={Apr}, pages={547-56}, abstract={ Based on a general theory of penetration of low-frequency Alfven oscillations from the magnetosphere to the Earth as developed in Leonovich and Mazur (1991), the authors have solved the problem of the distribution, over the Earth's surface, of a disturbed magnetic field for particular kinds of standing Alfven waves. Four kinds of oscillations have been considered, namely toroidal Alfven waves excited by a monochromatic magnetosonic wave, by a sudden magnetosonic impulse and by a stochastic magnetosound as well as poloidal monochromatic Alfven waves }, keywords={ geomagnetic variations magnetosphere micropulsations surface magnetic field geomagnetic variations micropulsations electromagnetic field standing Alfven waves magnetosphere oscillations toroidal Alfven waves monochromatic magnetosonic wave sudden magnetosonic impulse stochastic magnetosound poloidal monochromatic Alfven waves }, mynotes={UNREAD}, } @ARTICLE{CollisMar91, author={Collis, P.N. and Haggstrom, I.}, title={ High-latitude ionospheric response to a geomagnetic sudden commencement }, journal={J. Atmos. Terr. Phys. (UK), Journal of Atmospheric and Terrestrial Physics}, volume={53}, number={3-4}, year={1991}, month={Mar}, pages={241-8}, abstract={ A geomagnetic sudden commencement on 25 March 1987 was simultaneous with the onset of a large-scale depletion of F-region electron density observed by the EISCAT incoherent scatter radar in the dusk sector of the auroral zone (69.6 degrees N, 19.2 degrees E). Ionospheric signatures of the impulse were a transient increase in the northward component of the electric field and in the ion temperature. The maximum density depletion occurred about one hour after the magnetic impulse and corresponded to maxima in the electric field and ion temperature. Ionosonde measurements from stations south of the radar showed that the density depletion progressed steady equatorwards by more than 10 degrees of latitude during the two hours following the impulse. A brief recovery of F-region densities after the passage of the depletion was observed by the ionosondes, but the ionosphere above the radar remained depleted }, keywords={ F-region ionosphere AD 1987 03 25 magnetic storm substorm high latitude disturbance ionosphere magnetosphere interaction ionospheric response geomagnetic sudden commencement onset large-scale depletion F-region electron density impulse transient increase }, mynotes={UNREAD}, } @ARTICLE{Tsunomura90, title={ Case study of geomagnetic response to recurrent magnetospheric compressions }, journal={Journal of Geomagnetism and Geoelectricity}, volume={42}, number={11}, year={1990}, month={}, pages={1267-79}, abstract={ The transient oscillatory variation of geomagnetic field after a sudden impulse which occurred at 17/sup h/48/sup m/ UT on February 9, 1986 is examined. The oscillatory variation is predominant at the morning high latitudes but is also detected in low latitudes with nearly the same periods of about 180 seconds. A geostationary satellite, GOES 6, located near local noon recorded recurrent magnetopause crossings which correspond well to pulses in the oscillatory variation at Kakioka. It is also shown that the oscillatory variations at high latitudes are correlated with the time derivative of the horizontal component (DH) at Kakioka. Considering the meaning of Kakioka's DH, it is discussed that the oscillatory variations in the early morning auroral region may be caused by both field line oscillation and successive appearances and decays of global scale equivalent current systems due to recurrent magnetospheric compressions, while those at other local times at high latitudes are probably due to the latter }, keywords={ magnetosphere micropulsations solar wind AD 1986 02 09 SI solar wind magnetosphere interaction geomagnetic response transient oscillatory variation sudden impulse recurrent magnetopause crossings }, mynotes={UNREAD}, } @ARTICLE{WarneckeDec90, author={Warnecke, J. and Luhr, H. and Takahashi, K.}, title={ Observational features of field line resonances excited by solar wind pressure variations on 4 September 1984 }, journal={Planetary and Space Science}, volume={38}, number={12}, year={1990}, month={Dec}, pages={1517-31}, abstract={ In the course of the magnetic storm of 4 September 1984, after an inverse sudden impulse (SI), geomagnetic pulsations in the Pc 5-frequency range were observed at magnetometer stations in the local evening sector. They occurred at L-values of approximately 6, and lasted for several hours, their period increasing from about 320 to 550 s. In this study, two events of enhanced activity are discussed in some detail. During the 16:00 UT event, a favourable position of the AMPTE/IRM spacecraft allows conjugate observations in the Northern and Southern Hemispheres and in the magnetosphere. This constellation permits a precise determination of the wave node. During a later intensification around 18:00 UT, the AMPTE/CCE spacecraft near local noon monitored poloidal waves, obviously driving the pulsations on the ground. Generally, the observations are consistent with the theory of field line resonance }, keywords={ magnetosphere micropulsations solar wind magnetosphere interaction micropulsation Pc 5 AD 1984 09 04 magnetic pulsation solar wind pressure variations magnetic storm inverse sudden impulse geomagnetic pulsations local evening sector wave node poloidal waves field line resonance }, mynotes={UNREAD}, } @ARTICLE{FarrugiaMay89, author={Farrugia, C.J. and Freeman, M.P. and Cowley, S.W.H. and Southwood, D.J. and Lockwood, M. and Etemadi, A.}, title={ Pressure-driven magnetopause motions and attendant response on the ground }, journal={Planetary and Space Science}, volume={37}, number={5}, year={1989}, month={May}, pages={589-607}, abstract={ The terrestrial magnetopause suffered considerable sudden changes in its location on 9-10 September 1978. These magnetopause motions were accompanied by disturbances of the geomagnetic field on the ground. The authors present a study of the magnetopause motions and the ground magnetic signatures using, for the latter, 10 s averaged data from 14 high latitude ground magnetometer stations. Observations in the solar wind (from IMP8) are employed and the motions of the magnetopause are monitored directly by the spacecraft ISEE 1 and 2. With these coordinated observations the authors are able to show that it is the sudden changes in the solar wind dynamic pressure that are responsible for the disturbances seen on the ground. At some ground stations evidence is seen of a 'ringing' of the magnetospheric cavity, while at others only the initial impulse is evident }, keywords={ magnetosphere pressure driven motion magnetosphere magnetic activity AD 1978 09 09 to 10 magnetopause }, mynotes={UNREAD}, } @ARTICLE{Rezhenov87, author={Rezhenov, B.V. and Lyatskiy, V.B.}, title={ Current system of a sudden impulse, Si }, journal={Geomagnetizm i Aeronomiya}, volume={27}, number={2}, year={1987}, month={}, pages={}, abstract={ The compression of the magnetosphere during an Si produces a change in the boundary separating the regions of direct and reverse convection. As a result, a current system develops in the ionosphere which approximately coincides with that observed at the time of the Si. The electric-field disturbance is maximal in a narrow zone bordering on the polar-cap boundary and is always equal there to double the value of the undisturbed field, whereas the width of this zone increases in proportion to the Si. The propagation of the electric-field disturbance generated at the time of an Si along magnetic lines of force leads to the excitation of high-amplitude resonance oscillations of the lines of force }, keywords={ ionosphere magnetosphere electric current system SI boundary position change sudden impulse Si compression magnetosphere reverse convection ionosphere electric-field disturbance polar-cap boundary high-amplitude resonance oscillations }, mynotes={UNREAD}, } @ARTICLE{Parkhomov85, title={ Fine structure of the preliminary impulse of the sudden commencement of magnetic storms }, journal={Geomagnetizm i Aeronomiya}, volume={25}, number={3}, year={1985}, month={}, pages={}, abstract={ It is shown that the preliminary impulse of a magnetic storm sudden commencement has a fine structure in the form of a train of decaying oscillations in the region Pc 2-3 with a duration of less than 2 minutes. The excitation of the oscillations is linked to the propagation of a fast magnetosonic wave, which is generated by the interaction of the interplanetary shock wave with the magnetosphere }, keywords={ magnetic storms micropulsations SC fine structure magnetosphere magnetic storm Pc 2 Pc 3 micropulsation preliminary impulse sudden commencement train of decaying oscillations excitation fast magnetosonic wave }, mynotes={UNREAD}, } @ARTICLE{KikuchiMar86, title={ Evidence of transmission of polar electric fields to the low latitude at times of geomagnetic sudden commencements }, journal={Journal of Geophysical Research}, volume={91}, number={A3}, year={1986}, month={Mar}, pages={3101-5}, abstract={ The HF Doppler frequency deviation associated with the geomagnetic sudden commencement (sc), called SCF, consists of the negative preliminary frequency deviation (PFD) and the succeeding positive main frequency deviation (MFD) when observed during the night at geomagnetic low latitude (geomagnetic latitude=25 degrees ). This type of HF Doppler frequency deviation, SCF(-or+), corresponds to the sc(+) at low latitude and the sc(-or+) (=sc*) at high latitude. The SCF(-or+) starts earlier than the low latitude sc by 50 s, while it occurs simultaneously with the high latitude sc* within a time accuracy of 10 s. This result implies that the negative PFD of the nighttime SCF(-or+) is caused by a dusk-to-dawn polar electric field responsible for the preliminary reverse impulse (PRI) of sc*, the occurrence of which is earlier than the occurrence of the world-wide geomagnetic increase. Consequently, the magnetospheric electric field generated at the onset of sc is transmitted to the low-latitude ionosphere by way of the polar ionosphere, earlier than the direct transmission through the magnetosphere by compressional hydromagnetic waves }, keywords={ magnetic storms magnetosphere magnetic storm magnetosphere PFD SC MFD PRI transmission polar electric fields low latitude geomagnetic sudden commencements HF Doppler frequency deviation sudden commencement SCF negative preliminary frequency deviation main frequency deviation dusk-to-dawn polar electric field preliminary reverse impulse onset polar ionosphere }, mynotes={UNREAD}, } @ARTICLE{KikuchiDec85, author={Kikuchi, T. and Araki, T.}, title={ Preliminary positive impulse of geomagnetic sudden commencement observed at dayside middle and low latitudes }, journal={Journal of Geophysical Research}, volume={90}, number={A12}, year={1985}, month={Dec}, pages={12195-200}, abstract={ It is found that an impulsive geomagnetic increase, named the preliminary positive impulse (PPI), often precedes the main impulse (MI) of geomagnetic sudden commencement at the dayside middle latitude (Memambetsu). The duration time of the PPI is about 1 min, and the average magnitude is 16 nT. The PPI also appears near the geomagnetic equator (Guam), although the occurrence is less frequent. No equatorial enhancements are present in the PPI, while the MI is enhanced appreciably at Guam. Most of PPI's accompany an electric field with a westward component in the ionospheric F region, as observed with the HF Doppler technique. These observational results lead to a conclusion that the PPI is transmitted from above the ionosphere by a compressional hydromagnetic wave }, keywords={ magnetic storms PPI preliminary impulse magnetic storm magnetosphere Preliminary positive impulse geomagnetic sudden commencement dayside low latitudes main impulse middle latitude compressional hydromagnetic wave }, mynotes={UNREAD}, } @ARTICLE{BaumjohannMay84, author={Baumjohann, W. and Junginger, H. and Haerendel, G. and Bauer, O.H.}, title={ Resonant Alfven waves excited by a sudden impulse }, journal={Journal of Geophysical Research}, volume={89}, number={A5}, year={1984}, month={May}, pages={2765-9}, abstract={ On March 6, 1979, long-period hydromagnetic waves were excited in the forenoon magnetosphere by a sudden impulse (SI). The plasma drift velocity and magnetic field oscillations associated with these waves were observed by the electron gun experiment and the magnetometer, respectively, onboard the GEOS 2 satellite in the equatorial plane. The waves had both compressional and transverse components and had their probable source in a single, tailward traveling, large-scale magnetopause surface 'wavelet' (i.e. a single rarefaction/compression pulse) caused by the passage of an interplanetary shock front. This surface wavelet apparently coupled into the inner magnetosphere via the field line resonance mechanism. The satellite observations and the Poynting vectors calculated from these are consistent with a location of the resonance region earthward of GEOS 2 during the first 5 min after the SI while the satellite was located just inside the resonance region at later times }, keywords={ geomagnetic variations interplanetary matter magnetohydrodynamic waves magnetosphere micropulsations solar wind Earth radii 006.6 AD 1979 03 06 MHD waves resonant Alfven waves compressional wave component tailward travelling magnetopause surface wavelet surface wavelet-inner magnetosphere coupling transverse wave component resonance region location solar wind-magnetosphere interaction Pc 4-5 micropulsations March 6, 1979 long-period hydromagnetic waves forenoon magnetosphere sudden impulse plasma drift velocity magnetic field oscillations electron gun experiment magnetometer GEOS 2 satellite equatorial plane single rarefaction/compression pulse interplanetary shock front field line resonance mechanism satellite observations Poynting vectors }, mynotes={UNREAD}, } @ARTICLE{KikuchiSep79, title={ Transient response of uniform ionosphere and preliminary reverse impulse of geomagnetic storm sudden commencement }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={41}, number={9}, year={1979}, month={Sep}, pages={917-25}, abstract={ Ionospheric propagation of magnetic disturbance due to a suddenly impressed source field is studied by the use of the Laplace transform method. In the E-region, assumed to be an anisotropic metallic medium, the mode is a diffusion or a Schrodinger type wave according to whether the propagation is perpendicular or parallel to the static magnetic field. Analytical solutions are used to examine whether the preliminary reverse impulse (PRI) of geomagnetic storm sudden commencement (SSC) is produced by the direct incidence of hydromagnetic waves on the ionosphere. No PRIs are obtained under both the polar and equatorial condition, while a small PRI-like impulse appears transiently in the polar case. From a viewpoint that the equatorial PRI is caused by the polar electric field communicated from the magnetosphere, the solutions are also used to find a possible mode for the instantaneous transmission of the polar electric field to the equator }, keywords={ atmospheric electricity atmospheric electromagnetic wave propagation E-region geomagnetic variations guided electromagnetic wave propagation ionosphere magnetic storms magnetosphere transient response preliminary reverse impulse geomagnetic storm sudden commencement suddenly impressed source field Laplace transform method E-region anisotropic metallic medium Schrodinger type wave static magnetic field equatorial PRI magnetic disturbance ionosphere propagation uniform ionosphere transient response magnetosphere polar electric field instantaneous transmission hydromagnetic waves incidence diffusion propagation mode Earth ionosphere waveguide propagation }, mynotes={UNREAD}, } @ARTICLE{RastogiMar78, title={ Theory for preliminary negative impulse in storm sudden commencement in H at equatorial stations }, journal={Proceedings of the Indian Academy of Sciences, Section A}, volume={87A}, number={3}, year={1978}, month={Mar}, pages={57-60}, abstract={ It is shown that the storm sudden commencement (SSC) in the H field at a low latitude station consists of only a positive excursion when the interplanetary shock due to the solar plasma impinging on the magnetosphere is associated with a southward excursion of the interplanetary magnetic field (IMF). When the signature of SCC at a low latitude station consists of a preliminary negative excursion preceding the main positive excursion of the H field, the solar plasma causing the compression is associated with a northward excursion of the IMF. It is suggested that the signature of SCC(H) at equatorial stations is the result of the combined effect of the compression of magnetosphere by the solar effects of the compression of magnetosphere by the solar plasma and the electric field effects associated with the velocity of the solar plasma and interacting with the northward component of the interplanetary field }, keywords={ geomagnetism interplanetary magnetic fields magnetic storms magnetosphere negative impulse storm sudden commencement equatorial stations interplanetary shock solar plasma magnetosphere interplanetary magnetic field geomagnetic horizontal component field excursions }, mynotes={UNREAD}, } @ARTICLE{RastogiOct80, title={ Equatorial storm sudden commencements & interplanetary magnetic field }, journal={Indian Journal of Radio & Space Physics}, volume={9}, number={5}, year={1980}, month={Oct}, pages={173-81}, abstract={ A comparison is made of the signatures of interplanetary (IP) shocks in the B and theta plots of interplanetary magnetic field (IMF) data of satellites Explorer 33, 34, and 35 and in the H magnetograms at ground observatories within the equatorial electrojet belt, Huancayo, Addis Ababa and Trivandrum associated with major storm sudden commencements during 1967-70. The IP shocks showing sudden increase of the scalar value of IMF were followed by a purely positive sudden increase of H, at any of the magnetic observatories, either on the dayside or the nightside of the Earth. The IP shocks identified by a sudden increase of B and with the northward turning of the latitude theta (positive Delta B/sub z/) were associated with purely positive sudden commencement (SC) at the observatories in the nightside but at the equatorial observatories in the dayside of the earth the signature of the shock was a SC in H with a preliminary negative impulse followed by the main positive excursion (SC-+). It is suggested that the SC in H at low latitudes are composed of two effects, one due to hydromagnetic pressure on the magnetosphere by the solar plasma and the other due to the induced electric field associated with the solar wind velocity }, keywords={ magnetic storms solar wind interplanetary magnetic field major storm sudden commencement magnetosphere shock wave magnetic storm geomagnetic storm equatorial solar wind AD 1967 to 1970 }, mynotes={UNREAD}, } @ARTICLE{ArakiApr77, title={ Global structure of geomagnetic sudden commencements }, journal={Planetary and Space Science}, volume={25}, number={4}, year={1977}, month={Apr}, pages={373-84}, abstract={ The geomagnetic sudden commencements (SSCs) are analyzed by the use of rapid-run magnetograms from eight American zone stations (Koror, Guam, Honolulu, Tucson, Fredericksburg, Sitka, College and Pt. Barrow). The occurrence rate of the equatorial SC* reaches the maximum value of 60-70% in the early afternoon. The type (SC* or pure SC without a preliminary reverse impulse) of an SSC at the dayside equator coincides well with that in the afternoon side high latitudes. When a pure SC is observed at Koror in the early afternoon, the other seven stations also observe pure SCs, and their onset is almost simultaneous at all the stations. The dayside equatorial SC* usually corresponds to SC*s in afternoon side high latitudes and pure SCs in middle latitudes (Honolulu and/or Tucson). The results are interpreted as showing the polar origin of the equatorial preliminary reverse impulse and the existence of two types of the interaction between the magnetosphere and the shock or discontinuity in the solar wind during SSC }, keywords={ magnetic storms magnetosphere geomagnetic sudden commencements magnetosphere magnetic storms solar wind discontinuity global structure rapid run magnetograms equatorial region }, mynotes={UNREAD}, } @ARTICLE{SchutzMay74, author={Schutz, S. and Adams, G.J. and Mozer, F.S.}, title={ Electric and magnetic fields measured during a sudden impulse }, journal={Journal of Geophysical Research}, volume={79}, number={13}, year={1974}, month={May}, pages={2002-4}, abstract={ The electric field in the ionosphere and the magnetic field at the Earth's surface in the mid-latitude region were both measured during a sudden impulse. Ionospheric conductivities deduced from this data were consistent with expectations, thus suggesting that the fluctuations in the magnetic field at the Earth's surface were caused by overhead ionospheric currents that were driven by an electric field associated with the sudden impulse }, keywords={ atmospheric electricity geomagnetic variations ionosphere magnetosphere magnetic fields sudden impulse electric field ionosphere Earth's surface ionospheric conductivities }, mynotes={UNREAD}, } @ARTICLE{PytteJan74, author={Pytte, T. and Bjordal, J. and Bronstad, K. and Singstad, I. and Stadsnes, J. and Trefall, H. and Ullaland, S. and Brown, R.R. and Karas, R.H.}, title={ Large-scale auroral-zone electron precipitation event, briefly interrupted during a negative magnetic impulse }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={36}, number={1}, year={1974}, month={Jan}, pages={29-42}, abstract={ Multiple balloon recordings of bremsstrahlung X-rays from a large scale auroral-zone electron precipitation event are presented. Additional riometer recordings show that it extended from noon, via dusk, to midnight. The X-ray observations show electron precipitation over a range of L-values from approximately=5.5 to 7.5. This was briefly interrupted during a negative sudden impulse in the geomagnetic field. A close similarity between variations in the X-ray fluxes and locally recorded variations in the geomagnetic field was observed. Magnetic records from around the auroral zone suggest that the precipitation was related to an asymmetric magnetospheric convection system }, keywords={ atmospheric electron precipitation geomagnetic variations magnetic storms magnetosphere electron precipitation negative magnetic impulse multiple balloon recordings bremsstrahlung X-rays riometer recordings asymmetric magnetospheric convection system }, mynotes={UNREAD}, } @ARTICLE{BrownNov73, author={Brown, R.R. and Driatsky, V.M.}, title={ Further studies of ionospheric and geomagnetic effects of sudden impulses }, journal={Planetary and Space Science}, volume={21}, number={11}, year={1973}, month={Nov}, pages={1931-5}, abstract={ From riometer records for the sudden impulse event of 4 February 1969, it is shown that ionospheric absorption accompanying a sudden impulse has the same type of latitude and longitude variations found for sudden commencement events. In addition, an examination of magnetograms at College, Alaska shows that some positive sudden impulses may trigger negative bays around local midnight, similar to the recent results for sudden commencements }, keywords={ geomagnetism ionosphere geomagnetic effects sudden impulses riometer records 4 February 1969 ionospheric absorption sudden commencement events magnetograms negative bays ionospheric effects }, mynotes={UNREAD}, } @ARTICLE{BrownSep73, title={ Sudden commencement and sudden impulse absorption events at high latitudes }, journal={Journal of Geophysical Research}, volume={78}, number={25}, year={1973}, month={Sep}, pages={5698-702}, abstract={ Observations of sudden commencement absorption (SCA) and sudden impulse absorption events at the south pole (74.2 degrees invariant latitude) show that these events are concentrated on the dayside of the magnetosphere. Although the majority of the events were preceded by substorm activity in the midnight sector, SCA events were observed after prolonged magnetic quiet. This finding indicates the presence of a source, less conspicuous than sub-storm processes in the magnetotail, that supplies electrons in the region of quasi-trapping }, keywords={ magnetic storms sudden impulse absorption events high latitudes sudden commencement absorption south pole substorm activity midnight sector magnetotail electrons dayside magnetosphere }, mynotes={UNREAD}, } @ARTICLE{BrownApr73, title={ A study of ionospheric absorption in conjugate regions produced by storm sudden commencements and sudden impulses in the geomagnetic field }, journal={Journal of Geophysical Research}, volume={78}, number={10}, year={1973}, month={Apr}, pages={1668-72}, abstract={ Riometer data from Syowa, Antarctica, and Reykjavik, Iceland, were analyzed for the occurrence of sudden commencement (sc) and sudden impulse (si) absorption events over a 35-month period (February 1967 to December 1969). The results of this study include the fraction of sc and si that produce ionospheric absorption at L=6.3, the fraction of sc and si events that show absorption effects in conjugate regions, and the magnetic local time distributions of these events. The occurrence probability for conjugate events, plus other spatial features of these events, suggests a scale size of approximately 6*10/sup 4/ km for solar plasma at the boundary of the magnetosphere }, keywords={ geomagnetism ionospheric electromagnetic wave propagation magnetic storms solar plasma magnetosphere ionospheric absorption storm sudden commencements sudden impulses geomagnetic field ionospheric conjugate regions }, mynotes={UNREAD}, } @ARTICLE{BarcusNov72, author={Barcus, J.R. and Brown, R.R. and Karas, R.H. and Rosenberg, T.J. and Trefall, H. and Bronstad, K. and Kodama, M.}, title={ Auroral X-ray and conjugate ionospheric absorption observations of an electron precipitation event accompanying a sudden impulse in the geomagnetic field }, journal={Journal of Geophysical Research}, volume={77}, number={31}, year={1972}, month={Nov}, pages={6294-7}, abstract={ Considers an example of sudden impulse electron precipitation in the auroral zone. These observations were obtained near the dawn meridian and include both bremsstrahlung data at balloon altitude and ionospheric absorption of cosmic radio noise. This event, in contrast with those reported previously, shows rapid variations in the electron flux; in addition, riometer observations at conjugate sites (Reykjavik, Iceland, and Syowa, Antarctica) show that the electron precipitation was essentially similar and simultaneous at this longitude }, keywords={ atmospheric electricity aurora electromagnetic wave absorption geomagnetism ionospheric electromagnetic wave propagation X-rays auroral X-ray conjugate ionosphere absorption observations electron precipitation event sudden impulse geomagnetic field auroral zone dawn meridian riometer observations rapid electron flux variations }, mynotes={UNREAD}, } @ARTICLE{OndohJan71, title={ Hydromagnetic interpretation of high latitude sudden impulse }, journal={Journal of the Radio Research Laboratories}, volume={18}, number={95}, year={1971}, month={Jan}, pages={19-33}, abstract={ The behavior of sudden impulses (si) observed in high latitudes is compared with the theoretical si behavior inferred from the solar wind compression. This comparison makes it apparent that the high latitude si must be treated hydromagnetically. The high latitude amplitude of transverse hydromagnetic waves propagated from the magnetospheric equatorial plane is computed by conservation of the geomagnetic flux in a tube of force and of the power flux of transverse hydromagnetic waves along the geomagnetic field lines using an appropriate wave amplitude on the magnetospheric equatorial plane. The latitudinal variation of the theoretical wave amplitude taking account of the ionosphere effect on the hydromagnetic waves agree well with the steep increase of observed si (or pc 5) amplitude from about 60 degrees to about 70 degrees in geomagnetic latitude. The si amplitude decrease observed at latitudes higher than 70 degrees may be due to the source distribution of transverse hydromagnetic waves in magnetosphere at the time of si. The transit time of transverse hydromagnetic waves along the L=5 field line from the equatorial plane to the auroral zone which is calculated for the collisionless model of ion density distribution is shorter than the transit time of fast mode hydromagnetic waves from 5 earth radii to the earth on the equatorial plane. This situation can explain an earlier occurrence of the si observed at high latitudes }, keywords={ atmospheric electricity ionosphere high latitude sudden impulse solar wind compression transverse hydromagnetic waves magnetospheric equatorial plane geomagnetic flux ionospheric effect ion density distribution }, mynotes={UNREAD}, } @ARTICLE{CahillNov70, author={Cahill, L.J. and Jr. and Patel, V.L.}, title={ Observation of sudden impulses in the inner magnetosphere: Explorer 26 }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={51}, number={11}, year={1970}, month={Nov}, pages={814}, abstract={ The low-latitude orbit of the Explorer 26 satellite, with apogee near five earth radii, samples magnetic field in the inner magnetosphere for about 15 hours a day. These continuous data within L=2 to 6 afford good opportunity to study magnetic field variations. The authors have analyzed the data during period of March-September, 1965 in order to correlate sudden impulse (SI) variations with the surface observations. About twenty events of SI show the amplitude correlations in the satellite and the surface data confirming previous observations by Explorer 12 and ATS-1. Several of these events can be understood as compressional changes generated by the movement of the magnetopause. However, it becomes necessary to consider magnetospheric currents to explain complex data in certain SI events }, keywords={ geomagnetic variations geomagnetism magnetosphere upper atmosphere sudden impulses inner magnetosphere Explorer 26 magnetic field variations currents }, mynotes={UNREAD}, } @ARTICLE{HayashiSep68, author={Hayashi, K. and Kokubun, S. and Oguti, T.}, title={ Polar chorus emission and worldwide geomagnetic variation }, journal={Report of Ionosphere and Space Research in Japan}, volume={22}, number={3}, year={1968}, month={Sep}, pages={149-60}, abstract={ Comparisons are made between VLF chorus emission data observed at Syowa Base, Antarctica, and magnetograms from low latitude stations. It is found the VLF chorus variations are closely related to ssc, si and also worldwide changes in magnetic field, which are thought to be caused by compressions or expansions of the magnetosphere. It is shown that a sudden impulse in geomagnetic field is associated in most cases with polar chorus variation in the daytime, and that a positive impulse is accompanied by a sudden enhancement or commencement of chorus. A negative impulse is associated with sudden decrease or fade-out of chorus emission. The center frequency of chorus tends to increase at times of positive magnetic variations, and the rate of this frequency change is closely related to the magnitude of the corresponding magnetic variation. It is suggested that polar chorus originated in electron cyclotron instability in the magnetosphere, L=6 approximately 10 }, keywords={ geomagnetic variations }, mynotes={UNREAD}, } @ARTICLE{SiscoeAug68, author={Siscoe, G.L. and Formisano, V. and Lazarus, A.J.}, title={ Relation between geomagnetic sudden impulses and solar wind pressure changes-an experimental investigation }, journal={Journal of Geophysical Research}, volume={73}, number={15}, year={1968}, month={Aug}, pages={4869-74}, abstract={ Theoretically the relation between the size of a geomagnetic sudden impulse Si and the associated change in the solar wind stagnation pressure P/sub s/ is given by i=k ((P/sub s/(2))/sup 1///sup 2/- (P/sub s/(1))/sup 1///sup 2/) where (1) and (2) refer to pressures before and after the event and k is a proportionality constant. We have determined k experimentally using the M.I.T. solar wind measurements on Pioneer 6. The results support the general functional relation given above; however, the experimental value for k is approximately /sup 1///sub 2/ that expected theoretically. This discrepancy was also found in a direct comparison of geomagnetic field strength and different solar wind pressures on quiet days. Several factors might contribute to the difference, such as the seasonal inclination of the dipole axis, the solar wind magnetic field, and the magnetospheric particle population }, keywords={ geomagnetic variations Sun }, mynotes={UNREAD}, } @ARTICLE{StrangewayDec88, author={Strangeway, R.J. and Scarf, F.L. and Zanetti, L.J. and Klumpar, D.M.}, title={ AMPTE CCE plasma wave measurements during magnetospheric compressions }, journal={Journal of Geophysical Research}, volume={93}, number={A12}, year={1988}, month={Dec}, pages={14357-68}, abstract={ The near-equatorial orbit of the Charge Composition Explorer (CCE) has an apogee of 9 R/sub E/, and the spacecraft frequently crosses the magnetopause when it is at its maximum range and within a few hours of local noon. On rare occasions the disturbed solar wind compresses the magnetosphere so much that CCE passes through the bow shock into the interplanetary medium. For these events, CCE is near apogee with a speed that is very low with respect to that of the nominal standing bow shock surface, and the spacecraft instruments are very well positioned to investigate details of bow shock structure and motion. The authors summarize plasma wave observations for the CCE bow shock crossings of November 1, 1984, and February 8, 1986, and then focus attention on the 1984 multiple shock crossing events. For this case they demonstrate that the characteristic features in the wave measurements provide unique signatures for the magnetosheath, bow shock, and foreshock. The most striking signature in the wave data is the presence of a relatively constant signal of 10/sup -6/ V m/sup -1/ Hz/sup -1/2/ observed in the 30-kHz channel when the spacecraft is in the magnetosheath }, keywords={ magnetosphere solar wind magnetosphere interaction AD 1984 11 01 AD 1986 02 08 plasma wave magnetospheric compressions bow shock interplanetary medium bow shock structure magnetosheath foreshock }, mynotes={UNREAD}, } @ARTICLE{SharberApr96, author={Sharber, J.R. and Link, R. and Frahm, R.A. and Winningham, J.D. and Lummerzheim, D. and Rees, M.H. and Chenette, D.L. and Gaines, E.E.}, title={ Validation of UARS particle environment monitor electron energy deposition }, journal={Journal of Geophysical Research}, volume={101}, number={D6}, year={1996}, month={Apr}, pages={9571-82}, abstract={ One of the primary goals of the particle environment monitor (PEM) on the Upper Atmosphere Research Satellite is the determination of the solar and magnetospheric particle energy inputs to the upper and middle atmosphere. This is accomplished by measuring the incident particle spectra and computing energy deposition and ionization rates as functions of altitude. The particle spectral measurements are made by detectors covering the energy range 5 eV to 5 MeV for electrons and 5 eV to 150 MeV for protons. An X-ray camera provides global-scale images and energy spectra of À3 to 100 keV bremsstrahlung X-rays produced by electrons incident on the atmosphere. Thus PEM measures particles which lose their energy in an atmospheric region extending from the thermosphere down to À50 km, with the altitude of associated bremsstrahlung X-rays reaching À25-km levels. PEM validation documented in this report has involved an assessment of the data quality of each PEM component instrument, intercalibration of individual instruments, and validation of the computations of the rates of electron energy deposition into the atmosphere. The energy deposition rate calculations are validated against existing energy deposition codes over the complete energy range of PEM measurements }, keywords={ atmospheric ionisation atmospheric measuring apparatus atmospheric radiation cosmic ray electrons cosmic ray energy spectra cosmic ray protons geophysical aspects of cosmic rays magnetosphere solar cosmic ray particles solar wind UARS particle environment monitor electron energy deposition Upper Atmosphere Research Satellite magnetosphere solar particle energy upper atmosphere middle atmosphere ionization rates altitude X-ray camera thermosphere bremsstrahlung intercalibration data quality 5 eV to 150 MeV 25 to 400 km }, mynotes={UNREAD}, } @ARTICLE{SharberJun93, author={Sharber, J.R. and Frahm, R.A. and Winnigham, J.D. and Biard, J.C. and Lummerzheim, D. and Rees, M.H. and Chenette, D.L. and Gaines, E.E. and Nightingale, R.W. and Imhof, W.L.}, title={ Observations of the UARS Particle Environment Monitor and computation of ionization rates in the middle and upper atmosphere during a geomagnetic storm }, journal={Geophysical Research Letters}, volume={20}, number={12}, year={1993}, month={Jun}, pages={1319-22}, abstract={ During the geomagnetic storm of 8-9 November 1991, the Upper Atmosphere Research Satellite (UARS), orbiting at 585 km, passed through the expanded auroral zone during portions of several successive orbits. The instruments of the UARS Particle Environment Monitor (PEM) observed particle precipitation, auroral X-ray emissions, and large-scale disturbances in the geomagnetic field during this time. The authors present observations made by the PEM instruments during this storm and compute ionization and energy deposition rates as functions of altitude in the middle and upper atmosphere by incident electrons and positive ions in the storm interval. The suite of PEM instruments provides a systematic measurement of energetic particles and their associated X-rays over an energy range not fully covered by previous satellite missions. In this energy range the ionization and dissociation rate in the atmosphere may be inferred from the upper stratosphere to the thermosphere. The impact on the chemistry of the region is investigated }, keywords={ atmospheric elementary particle precipitation atmospheric ionisation atmospheric radiation atmospheric thermodynamics aurora ionosphere magnetic storms mesosphere thermosphere middle atmosphere ionisation mesosphere ionisation rates-altitude relation AD 1991 11 08 to 09 auroral electron precipitation X-ray energy range molecular dissociation incident X-ray intensity integrated X-ray flux ionosphere aeronomy UARS Particle Environment Monitor ionization rates upper atmosphere geomagnetic storm 8-9 November 1991 Upper Atmosphere Research Satellite expanded auroral zone particle precipitation auroral X-ray emissions energy deposition rates incident electrons positive ions PEM instruments energetic particles dissociation rate upper stratosphere thermosphere 40 to 400 km 3 eV to 3 MeV 585 km 3 to 100 keV }, mynotes={UNREAD}, } @ARTICLE{WinninghamJun93, author={Winningham, J.D. and Sharber, J.R. and Frahm, R.A. and Burch, J.L. and Faker, N. and Black, R.K. and Blevins, V.A. and Andrews, J.P. and Rudzki, J. and Sablik, M.J. and Chenette, D.L. and Datlowe, D.W. and Gaines, E.E. and Imhof, W.I. and Nightingale, R.W. and Reagan, J.B. and Robinson, R.M. and Schumaker, T.L. and Shelley, E.G. and Vondrak, R.R. and Voss, H.D. and Bythrow, P.F. and Anderson, B.J. and Potemra, T.A. and Zanetti, L.J. and Holland, D.B. and Rees, M.H. and Lummerzheim, D. and Reid, G.C. and Roble, R.G. and Clauer, C.R. and Banks, P.M.}, title={ The UARS particle environment monitor }, journal={Journal of Geophysical Research}, volume={98}, number={D6}, year={1993}, month={Jun}, pages={10649-66}, abstract={ The overall objective of the particle environment monitor (PEM) is to provide comprehensive measurements of both local and global energy inputs into the Earth's atmosphere by charged particles and Joule dissipation using a carefully integrated set of instruments. PEM consists of four instruments: the atmospheric X-ray imaging spectrometer (AXIS), the high-energy particle spectrometer (HEPS), the medium-energy particle spectrometer (MEPS), and the vector magnetometer (VMAG). AXIS provides global scale images and energy spectra of 3- to 100-keV bremsstrahlung X-rays produced by electron precipitation into the atmosphere. HEPS and MEPS provide in situ measurements of precipitating electrons in the energy range from 1 eV to 5 MeV and protons in the energy range from 1 eV to 150 MeV. Particles in this energy range deposit their energy in the atmosphere at altitudes extending from several hundred kilometers down to as low as approximately 30 km }, keywords={ atmospheric electron precipitation atmospheric proton precipitation atmospheric techniques ionospheric techniques UARS Upper Atmosphere Research Satellite measurement technique satellite remote sensing instrumentation equipment AXIS particle precipitation ionosphere upper atmosphere particle environment monitor charged particles Joule dissipation X-ray imaging spectrometer high-energy particle spectrometer medium-energy particle spectrometer vector magnetometer electron precipitation 1 eV to 150 MeV }, mynotes={UNREAD}, } @ARTICLE{SharberNov73, author={Sharber, J.R. and Heikkila, W.J.}, title={ Rocket and satellite observations of electron fluxes associated with an auroral arc system }, journal={EOS Trans. Am. Geophys. Union (USA), EOS Transactions of the AmericanGeophysical Union}, volume={54}, number={11}, year={1973}, month={Nov}, pages={1170-1}, abstract={ An instrumented rocket payload measured the auroral particle spectrum in the energy range 10 eV to 13 keV as the payload passed through and above the visible arc. The ISIS-1 satellite provided spectral measurements at an altitude of 750 km. The structure evident in the satellite particle data correlates well with the all-sky camera photograph taken as the satellite passed overhead. The electron spectra associated with the discrete nightside arcs are peaked at energies between 500 eV and 2 keV }, keywords={ atmospheric spectra aurora electron density upper atmosphere satellite observations electron fluxes auroral arc auroral particle spectrum 10 eV to 13 keV rocket observations 130 km 750 km }, mynotes={UNREAD}, } @ARTICLE{SharberJul72, author={Sharber, J.R. and Heikkila, W.J.}, title={ Fermi acceleration of auroral particles }, journal={Journal of Geophysical Research}, volume={77}, number={19}, year={1972}, month={Jul}, pages={3397-410}, abstract={ A number of nighttime acceleration mechanisms proposed in the literature are reviewed and rejected for the role of producing the kev nighttime auroral-particle fluxes. The authors suggest that longitudinal or Fermi acceleration, which results from the known magnetospheric convection, is the main nighttime auroral acceleration mechanism. The argument is supported by data obtained with the soft-particle spectrometer on Isis 1. In particular, the rotational scanning provided by the spinning satellite shows the regular change from a field-aligned pitch-angle distribution at high latitudes to a trapped distribution at low latitudes, reflecting a change from Fermi acceleration on the distant taillike field lines to betatron acceleration on the more dipolar field lines closer to the earth. The operation of the Fermi mechanism requires multiple bounces between hemispheres, and therefore a loss cone must develop at both 0 degrees and 180 degrees ; such distribution is shown by the Isis 1 data when the range of the pitch-angle scan is sufficiently wide. One other feature is evident in the data: a hardening of the spectrum at small pitch angles }, keywords={ acceleration aurora magnetosphere field aligned pitch angle distribution Fermi acceleration auroral particles magnetospheric convection trapped distribution betatron acceleration multiple bounces }, mynotes={UNREAD}, } @ARTICLE{SharberApr72, author={Sharber, J.R. and Heikkila, W.J.}, title={ Adiabatic processes in magnetospheric substorms }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={53}, number={4}, year={1972}, month={Apr}, pages={493}, abstract={ While the motion of moving magnetic field lines during substorms can be a useful concept, many aspects of magnetospheric substorm process can perhaps be better understood by considering the motion of charged particles in stationary crossed electric and magnetic fields. Simple considerations show that the geometry of the magnetotail is of vital importance, as is the presence of a dawn to dusk electric field. Adiabatic motion with conservation of the first and second invariants leads to ring currents and auroral particle energization respectively. The expansive phase starts when the beta of the trapped plasma in the tail approaches unity, permitting the magnetosheath plasma to push in on the dawn and dusk sides. That results in an increase in the local electric field intensity, and a speedup in the particle drift motions. Enhanced electron precipitation constitutes a field aligned current and produces a northward magnetic field which causes the poleward expansion of the aurora. The westward surge is also partly the result of this new magnetic field, but may also be affected by a change in the electric field pattern. During the recovery phase, the plasma sheet in the tail is replenished by convection from the dawn and dusk sides }, keywords={ aurora magnetic storms magnetosphere adiabatic processes magnetospheric substorms motion of charged particles stationary crossed electric and magnetic fields geometry magnetotail ring currents auroral particle energization magnetosheath plasma local electric field intensity particle drift motions enhanced electron precipitation field aligned current northward magnetic field poleward expansion westward surge aurora }, mynotes={UNREAD}, } @ARTICLE{Song-XueJul96, author={Song Xue, Thorne and R.M. and Summers, D.}, title={ Growth and damping of oblique electromagnetic ion cyclotron waves in the Earth's magnetosphere }, journal={Journal of Geophysical Research}, volume={101}, number={A7}, year={1996}, month={Jul}, pages={15457-66}, abstract={ The dispersive properties of oblique electromagnetic ion cyclotron (EMIC) waves are examined for conditions in the Earth's outer magnetosphere (L=7) when the energetic particle distribution has a high-energy tail modeled by a generalized Lorentzian distribution. For small wave normal angles, psi , to the ambient magnetic field, the wave growth and damping rates for a generalized Lorentzian distribution are smaller than those for a Maxwellian distribution (typically by a factor of 2), while for larger wave normal angles ( psi >or approximately=60 degrees ) the corresponding differences in the growth and damping rates are relatively small. For both the generalized Lorentzian and Maxwellian distributions, maximum wave growth due to hot proton temperature anisotropy occurs for parallel propagation, but significant wave growth can occur for wave normal angles ¹ psi ¹7, using Active Magnetosphere Particle Tracer Explorers/Charge Composition Explorer (AMPTE/CCE) magnetic field, ion, and plasma wave data. The analysis addresses the energy of protons that generate the waves, the ability of linear theory to predict both instability and stability, comparison of the predicted wave properties with the observed wave polarization and frequency, and the temperature anisotropy/parallel beta relation. The data were obtained during 24 intervals of electromagnetic ion cyclotron (EMIC) wave activity (active) and 24 intervals from orbits without EMIC waves (quiet). This is the same set of events used by Anderson and Fuselier [1994]. The active events are drawn from noon and dawn local times for which the wave properties are significantly different. For instability analysis, magnetospheric hot proton distributions required the use of multiple populations to analytically represent the data. Cyclotron waves are expected to limit the proton temperature anisotropy, A/sub p/=T/sub perpendicular to p//T/sub ¬¬p/-1, according to A/sub p/T/sub ///. This anisotropy drives unstable ion cyclotron waves which the authors believe can contribute to the generation of the Pc 1 waves which are detected }, keywords={ micropulsations solar wind magnetosphere interaction MHD wave micropulsation plasma shock wave magnetic pulsation fast shock wave Pc 1 ion temperature anisotropy sudden impulses mechanism generation dynamic pressure pulse bow shock weak fast mode shock magnetosheath unstable ion cyclotron waves }, mynotes={UNREAD}, } @ARTICLE{Rezhenov87, author={Rezhenov, B.V. and Lyatskiy, V.B.}, title={ Current system of a sudden impulse, Si }, journal={Geomagnetizm i Aeronomiya}, volume={27}, number={2}, year={1987}, month={}, pages={}, abstract={ The compression of the magnetosphere during an Si produces a change in the boundary separating the regions of direct and reverse convection. As a result, a current system develops in the ionosphere which approximately coincides with that observed at the time of the Si. The electric-field disturbance is maximal in a narrow zone bordering on the polar-cap boundary and is always equal there to double the value of the undisturbed field, whereas the width of this zone increases in proportion to the Si. The propagation of the electric-field disturbance generated at the time of an Si along magnetic lines of force leads to the excitation of high-amplitude resonance oscillations of the lines of force }, keywords={ ionosphere magnetosphere electric current system SI boundary position change sudden impulse Si compression magnetosphere reverse convection ionosphere electric-field disturbance polar-cap boundary high-amplitude resonance oscillations }, mynotes={UNREAD}, } @ARTICLE{UberoiJul88, title={ Alfven surface waves excited by a sudden impulse }, journal={Journal of Geophysical Research}, volume={93}, number={A7}, year={1988}, month={Jul}, pages={7595-7}, abstract={ The time-dependent evolution of an initial wave disturbance at the magnetospheric boundary as it is released in the presence of the sheared hydromagnetic flow in the magnetosphere is discussed for the simple case in which the shear in the Alfven speed is uniform. The uniform-shear assumption allows explicit solutions to be obtained which are useful in explaining the recent observations of resonant Alfven waves excited in the magnetosphere by a sudden impulse }, keywords={ magnetosphere plasma wave excitation SI Alfven surface waves sudden impulse time-dependent evolution initial wave disturbance magnetospheric boundary sheared hydromagnetic flow magnetosphere Alfven speed uniform-shear assumption resonant Alfven waves }, mynotes={UNREAD}, } @ARTICLE{ParkDec75, title={ Whistler observations during a magnetospheric sudden impulse }, journal={Journal of Geophysical Research}, volume={80}, number={34}, year={1975}, month={Dec}, pages={4738-40}, abstract={ Whistlers recorded at Siple, Antarctica (76 degrees S, 84 degrees W), show sudden changes in nose frequency (f/sub n/) in response to a magnetospheric sudden impulse (si) on June 9, 1973. These changes are partly due to changes in local magnetic field strength and partly due to the motion of the duct under the influence of induced electric field. This example is used to illustrate how ground-based VLF radio techniques can be used to monitor the dynamic response of the magnetosphere to shocks and discontinuities in the solar wind }, keywords={ magnetosphere whistlers magnetospheric sudden impulse Siple Antarctica nose frequency VLF radio techniques solar wind whistlers }, mynotes={UNREAD}, } @ARTICLE{SchutzMay74, author={Schutz, S. and Adams, G.J. and Mozer, F.S.}, title={ Electric and magnetic fields measured during a sudden impulse }, journal={Journal of Geophysical Research}, volume={79}, number={13}, year={1974}, month={May}, pages={2002-4}, abstract={ The electric field in the ionosphere and the magnetic field at the Earth's surface in the mid-latitude region were both measured during a sudden impulse. Ionospheric conductivities deduced from this data were consistent with expectations, thus suggesting that the fluctuations in the magnetic field at the Earth's surface were caused by overhead ionospheric currents that were driven by an electric field associated with the sudden impulse }, keywords={ atmospheric electricity geomagnetic variations ionosphere magnetosphere magnetic fields sudden impulse electric field ionosphere Earth's surface ionospheric conductivities }, mynotes={UNREAD}, } @ARTICLE{BurlagaJun69, author={Burlaga, L.F. and Ogilvie, K.W.}, title={ Causes of sudden commencements and sudden impulses }, journal={Journal of Geophysical Research}, volume={74}, number={11}, year={1969}, month={Jun}, pages={2815-25}, abstract={ The causes of 19 worldwide changes in the Earth's magnetic field, occurring between June and Dec 1967, were determined by examining magnetic field and plasma data for the solar wind nEar the Earth }, keywords={ geomagnetic variations interplanetary magnetic fields magnetosphere plasma solar corpuscular radiation }, mynotes={UNREAD}, } @ARTICLE{AndersonMay97, author={Anderson, B.J. and Phan, T.-D. and Fuselier, S.A.}, title={ Relationships between plasma depletion and subsolar reconnection }, journal={Journal of Geophysical Research}, volume={102}, number={A5}, year={1997}, month={May}, pages={9531-42}, abstract={ Observations in the subsolar magnetosheath show that the plasma depletion layer (PDL) is less pronounced for southward than for northward IMF. Since subsolar plasma depletion indicates pile-up of magnetic flux, the degree of plasma depletion should depend on the relative rates of flux transport via subsolar reconnection and flux advection by the solar wind flow. To identify the factors affecting plasma depletion, the authors consider the ratio D=E/sub r//E/sub sw/ where E/sub r/ is the reconnection electric field and E/sub sw/ is the imposed solar wind electric field. For a quasi-perpendicular subsolar bow shock D can be expressed in terms of magnetosheath parameters. Since PDL formation is suppressed when the subsolar bow shock is quasi-parallel, they restrict attention to quasi-perpendicular conditions. They show that D increases with increasing reconnection efficiency, magnetic shear at the magnetopause, and the magnetosheath magnetic field but decreases with increasing total perpendicular pressure (particle plus magnetic field) in the magnetosheath. By combining observations of the subsolar quasi-perpendicular magnetosheath from AMPTE/IRM and AMPTE/CCE they verify that the degree of plasma depletion is inversely correlated with D. Furthermore, they show that the greater prevalence of plasma depletion in the CCE data implies that the reconnection efficiency is lower for the CCE events and specifically that the reconnection efficiency depends roughly inversely on magnetosheath beta , for beta >1. Finally, the results show that all of the changes brought about by plasma depletion act to increase E/sub r/ so that some subsolar reconnection is likely to occur even for low magnetic shear. Thus the percentage of the magnetosheath magnetic field that participates in reconnection near the subsolar region does not act as a rectifier but remains positive for all shear angles, decreasing monotonically as the magnetic shear at the subsolar magnetopause changes from high to l }, keywords={ magnetosphere solar wind magnetosphere plasma depletion subsolar reconnection magnetic field line reconnection subsolar magnetosheath plasma depletion layer magnetic flux pile-up flux advection solar wind flow solar wind magnetosphere interaction quasi-perpendicular subsolar bow shock magnetic shear polar cap convection cell low shear reconnection }, mynotes={UNREAD}, } @ARTICLE{FuselierMar97, author={Fuselier, S.A. and Anderson, B.J. and Onsager, T.G.}, title={ Electron and ion signatures of field line topology at the low-shear magnetopause }, journal={Journal of Geophysical Research}, volume={102}, number={A3}, year={1997}, month={Mar}, pages={4847-63}, abstract={ Electrons above 50 eV are a sensitive indicator of field line topology at the magnetopause, particularly when the solar wind dynamic pressure is high and the shear across the boundary is low. AMPTE/CCE electron observations under conditions when these criteria are fulfilled indicate a clear topological transition from the magnetosheath to open field lines threading the magnetopause in the magnetosheath boundary layer (MSBL). Once across the magnetopause and in the low latitude boundary layer (LLBL), the fast moving electrons are no longer a good indicator of magnetic field topology. In particular, the counterstreaming electron observations in this region are not an indicator of a closed magnetic topology. Rather, the field topology continues to be open, and the counterstreaming occurs because electrons from the magnetopause region move rapidly enough along the LLBL magnetic field to make it to the ionosphere, mirror, and return to the observation point. Slower moving ions provide important additional information on magnetic field topology in the LLBL. The CCE observations discussed indicate that two types of solar wind ion distributions are observed in this layer. One type consists of a single, heated distribution which resembles somewhat the electron distribution in the layer. The other type consists of a unidirectional streaming distribution. The field-aligned velocity of this distribution is higher than in the adjacent magnetosheath. Combining these observations with magnetospheric ion observations (e.g. O/sup +/) in the LLBL and with electron observations in the MSBL, two distinct magnetic field topologies emerge for the low-shear magnetopause. The first, which gives rise to single, low-parallel-velocity and heated solar wind ion distributions in the LLBL, is magnetic reconnection poleward of the cusp, The second, which gives rise to unidirectional streaming solar wind ion distributions in the LLBL, is magnetic reconnection equatorward of the cusp. This type of }, keywords={ electrons magnetic fields magnetosphere positive ions magnetosheath boundary layer low latitude boundary layer AMPTE/CCE electron observations magnetic field line topology low-shear magnetopause solar wind dynamic pressure fast moving electrons counterstreaming electron observations field-aligned velocity magnetospheric ion observations O/sup +/ heated solar wind ion distributions magnetic reconnection unidirectional streaming solar wind ions 50 eV O }, mynotes={UNREAD}, } @ARTICLE{FuselierJun96, author={Fuselier, S.A. and Anderson, B.J.}, title={ Low-energy He/sup +/ and H/sup +/ distributions and proton cyclotron waves in the afternoon equatorial magnetosphere }, journal={Journal of Geophysical Research}, volume={101}, number={A6}, year={1996}, month={Jun}, pages={13255-65}, abstract={ Characteristics of low energy (À10 to 50 eV) H/sup +/ and He/sup +/ distributions in the afternoon magnetosphere from L=4 to 9 are studied using Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer (AMPTE/CCE) data. He/sup +/ distributions in this study routinely display features indicating resonant heating by proton cyclotron waves in the outer magnetosphere (L>7) whereas protons exhibit minimal evidence of heating. Low energy H/sup +/ distributions have T/sub perpendicular to />>T/sub ¹¹/ for L<5 but T/sub perpendicular to /<7. The change is due to a decrease in T/sub perpendicular to / with increasing L and is consistent with adiabatic cooling in the perpendicular direction as the ions convect sunward. By contrast, low-energy He/sup +/ distributions have T/sub perpendicular to />>T/sub ¹¹/ independent of L. The failure of the He/sup +/ to cool adiabatically indicates that He/sup +/ experiences transverse heating as it convects sunward through the outer magnetosphere. The occurrence of proton cyclotron waves in the afternoon magnetosphere is evaluated using AMPTE/CCE magnetometer data and shows that low energy ions convecting sunward from the afternoon plasmasphere have a 20% chance of being exposed to cyclotron waves by the time they reach L=5, 50% by L=6 and >95% by L=7. The majority of cyclotron waves in the early afternoon outer magnetosphere occur above the local He/sup +/ gyrofrequency and will interact resonantly with He/sup +/ but nonresonantly with H/sup +/. The combined effects of adiabatic sunward convection and interactions between the low-energy ions and proton cyclotron waves therefore account for the observed characteristics of both the H/sup +/ and He/sup +/ distributions in the afternoon magnetosphere }, keywords={ magnetosphere radiation belts low energy ion distribution He/sup +/ H/sup +/ plasma wave proton cyclotron wave afternoon equatorial magnetosphere AMPTE CCE adiabatic cooling cyclotron wave H He }, mynotes={UNREAD}, } @ARTICLE{AndersonJun96, author={Anderson, B.J. and Denton, R.E. and Fuselier, S.A.}, title={ On determining polarization characteristics of ion cyclotron wave magnetic field fluctuations }, journal={Journal of Geophysical Research}, volume={101}, number={A6}, year={1996}, month={Jun}, pages={13195-213}, abstract={ Polarization characteristics of magnetospheric proton cyclotron waves should provide definitive tests of mechanisms for wave propagation and growth. The authors present a minimum variance analysis technique called wave-step analysis, which requires only a few wave cycles of data. Tests of the wave-step procedure show that it is valid for signals with bandwidths up to À30% full width at half maximum and is therefore applicable to the majority of proton cyclotron wave events. Comparison of the wave-step and Fourier analyses for cyclotron wave events confirms that cyclotron wave fluctuations display features characteristic of nonstationary signals }, keywords={ magnetic fields magnetosphere plasma waves polarisation ion cyclotron wave magnetic field fluctuations polarization characteristics magnetospheric proton cyclotron waves wave propagation mechanism wave growth mechanism minimum variance analysis technique wave-step analysis proton cyclotron wave events Fourier analysis comparison nonstationary signals }, mynotes={UNREAD}, } @ARTICLE{AndersonOct94, author={Anderson, B.J. and Fuselier, S.A.}, title={ Response of thermal ions to electromagnetic ion cyclotron waves }, journal={Journal of Geophysical Research}, volume={99}, number={A10}, year={1994}, month={Oct}, pages={19413-25}, abstract={ Electromagnetic ion cyclotron waves generated by 10-50 keV protons in the Earth's equatorial magnetosphere will interact with the ambient low-energy ions also found in this region. The authors examine H/sup +/ and He/sup +/ distribution functions from approximately=1 to 160 eV using the Hot Plasma Composition Experiment instrument on AMPTE/CCE to investigate the thermal ion response to the waves. A total of 48 intervals were chosen on the basis of electromagnetic ion cyclotron (EMIC) wave activity: 24 with prevalent EMIC waves and 24 with no EMIC waves observed on the orbit. There is a close correlation between EMIC waves and perpendicularly heated ion distributions. For protons the perpendicular temperature increase is modest, about 5 eV, and is always observed at 90 degrees pitch angles. This is consistent with a nonresonant interaction near the equator. By contrast, He/sup +/ temperatures during EMIC wave events averaged 35 eV and sometimes exceeded 100 eV, indicating stronger interaction with the waves. Furthermore, heated He/sup +/ ions have X-type distributions with maximum fluxes occurring at pitch angles intermediate between field-aligned and perpendicular directions. The X-type He/sup +/ distributions are consistent with a gyroresonant interaction off the equator. The concentration of He/sup +/ relative to H/sup +/ is found to correlate with EMIC wave activity, but it is suggested that the preferential heating of He/sup +/ accounts for the apparent increase in relative He/sup +/ concentration by increasing the proportion of He/sup +/ detected by the ion instrument }, keywords={ magnetosphere electromagnetic ion cyclotron wave thermal ion magnetosphere plasma wave equatorial magnetosphere low-energy ions H/sup +/ He/sup +/ distribution function thermal ion response wave particle interaction EMIC wave protons nonresonant interaction gyroresonant interaction H He }, mynotes={UNREAD}, } @ARTICLE{FuselierAug94, author={Fuselier, S.A. and Anderson, B.J. and Gary, S.P. and Denton, R.E.}, title={ Inverse correlations between the ion temperature anisotropy and plasma beta in the Earth's quasi-parallel magnetosheath }, journal={Journal of Geophysical Research}, volume={99}, number={A8}, year={1994}, month={Aug}, pages={14931-6}, abstract={ Average proton parameters in the magnetosheath downstream from the quasi-perpendicular shock (the quasi-perpendicular magnetosheath) for high solar wind dynamic pressure conditions are observed to vary continuously from high-beta, low-temperature anisotropy to low-beta, high-temperature anisotropy. Observations and theory have shown that this inverse correlation is a direct consequence of pitch angle scattering by electromagnetic ion cyclotron (EMIC) waves, which regulate the anisotropy, restoring the plasma toward marginal stability. Although the previously documented spectral characteristics of EMIC waves are not evident downstream of the quasi-parallel bow shock, the inverse anisotropy-beta relation found in the quasi-perpendicular magnetosheath also holds in the quasi-parallel magnetosheath. This indicates that the EMIC instability regulates the ion anisotropy regardless of the shock geometry }, keywords={ magnetosphere plasma instability plasma waves ion temperature anisotropy plasma beta quasiparallel magnetosheath proton parameters quasiperpendicular shock solar wind dynamic pressure inverse correlation pitch angle scattering electromagnetic ion cyclotron waves EMIC waves stability quasiperpendicular magnetosheath ion anisotropy shock geometry }, mynotes={UNREAD}, } @ARTICLE{GaryApr94, author={Gary, S.P. and Convery, P.D. and Denton, R.E. and Fuselier, S.A. and Anderson, B.J.}, title={ Proton and helium cyclotron anisotropy instability thresholds in the magnetosheath }, journal={Journal of Geophysical Research}, volume={99}, number={A4}, year={1994}, month={Apr}, pages={5915-21}, abstract={ Both the protons and the helium ions of the terrestrial magnetosheath typically display T/sub perpendicular to />T/sub ///, where perpendicular to and // denote directions perpendicular and parallel to the background magnetic field. Observations of the highly compressed magnetosheath show an inverse correlation between these ion temperature anisotropies and the parallel proton beta . Computer simulations have demonstrated that these correlations are due to wave-particle scattering by electromagnetic ion cyclotron anisotropy instabilities. These correlations correspond to linear theory thresholds of the proton cyclotron and the helium cyclotron instabilities. This paper uses linear Vlasov theory and the assumption of a constant maximum growth rate to obtain closed-form expressions for these thresholds as a function of the relative helium density and the parallel proton beta in a parameter model of the magnetosheath }, keywords={ magnetosphere plasma instability cyclotron anisotropy instability threshold magnetosheath magnetosphere plasma instability ion cyclotron instability inverse correlation ion temperature anisotropy parallel proton beta simulation wave-particle scattering electromagnetic ion cyclotron anisotropy instabilities linear theory proton cyclotron Vlasov theory constant maximum growth rate closed form expression parameter model H He }, mynotes={UNREAD}, } @ARTICLE{GaryApr94, author={Gary, S.P. and McKean, M.E. and Winske, D. and Anderson, B.J. and Denton, R.E. and Fuselier, S.A.}, title={ The proton cyclotron instability and the anisotropy/ beta inverse correlation }, journal={Journal of Geophysical Research}, volume={99}, number={A4}, year={1994}, month={Apr}, pages={5903-14}, abstract={ Spacecraft observations in the strongly compressed subsolar magnetosheath show an inverse correlation between the proton temperature anisotropy (T/sub perpendicular to p//T/sub //p/>1 where perpendicular to and // denote directions perpendicular and parallel to the background magnetic field) and the parallel proton beta ( beta /sub //p/). This manuscript uses one-dimensional hybrid simulations of the proton cyclotron anisotropy instability in homogeneous electron-proton plasmas to study this correlation which may represent a limited closure relation for fluid theories of anisotropic space plasmas. The emphasis is on driven simulations which increase the temperature anisotropy by periodically reducing the magnetic-field-aligned velocities of the protons. The late-time states from ensembles of both initial value and driven simulations yield very similar expressions for the proton anisotropy/ beta /sub //p/ inverse correlation, and provide a basis for explaining differences between sheath observations from different spacecraft. The driven simulations also yield expressions for the maximum instability growth rate and the fluctuating field energy as functions of beta /sub //p/ and a parameter characterizing the anisotropy driver }, keywords={ magnetosphere plasma instability plasma instability magnetosphere proton cyclotron instability anisotropy beta inverse correlation strongly compressed subsolar magnetosheath proton temperature anisotropy parallel proton beta one dimensional hybrid simulation model anisotropy instability lectron-proton plasma closure relation maximum instability growth rate }, mynotes={UNREAD}, } @ARTICLE{Wenlong-DaiMay95, author={Wenlong Dai and Woodward, P.R.}, title={ A study for the interaction between solar wind irregularities and the magnetosphere through three-dimensional simulations }, journal={Physics of Plasmas}, volume={2}, number={5}, year={1995}, month={May}, pages={1725-34}, abstract={ In order to understand the interaction between solar wind irregularities and the closed magnetosphere, three-dimensional (3-D) computer simulations for ideal magnetohydrodynamical (MHD) equations are performed. This paper considers only the situation in which the initial interplanetary magnetic field is either parallel or antiparallel to the magnetospheric magnetic field. The irregularity is modeled as a ball, which initially moves toward the magnetosphere. The penetration of the irregularity in the 3-D model is found to be less efficient than in a two-dimensional (2-D) model. Through a comparison of the present results from 3-D simulations, not much difference has been found in the efficiency for the irregularity to penetrate into the magnetosphere between two situations in which the interplanetary field is parallel or antiparallel to the magnetospheric field }, keywords={ magnetosphere plasma magnetohydrodynamics solar wind solar wind irregularities magnetosphere interaction closed magnetosphere 3D computer simulations ideal MHD equations initial interplanetary magnetic field magnetospheric magnetic field penetration }, mynotes={UNREAD}, } @ARTICLE{LemaireJul91, author={Lemaire, J. and Roth, M.}, title={ Non-steady-state solar wind-magnetosphere interaction }, journal={Space Science Reviews}, volume={57}, number={1-2}, year={1991}, month={Jul}, pages={58-108}, abstract={ Most of the theories proposed to explain the interaction between the solar wind and the geomagnetic field are stationary descriptions based on ideal MHD. In the present review an alternative, non-stationary description is discussed. According to this description, most of the plasma-field irregularities, i.e., plasmoids, detected in the solar wind can penetrate inside the geomagnetic field beyond what is considered to be the mean position of the magnetopause. It is the patchy solar wind plasma impinging on the geomagnetic field which imposes rapidly changing and non-uniform boundary conditions over the whole outer magnetospheric surface. Some significant experimental geophysical observations supporting the impulsive penetration model are also discussed }, keywords={ astrophysical plasma magnetosphere solar wind solar wind-magnetosphere interaction non-stationary description plasma-field irregularities geomagnetic field boundary conditions impulsive penetration model }, mynotes={UNREAD}, } @ARTICLE{LabelleJul90, author={Labelle, J. and Kistler, L.M. and Treumann, R.A. and Baumjohann, W. and Sibeck, D.G. and Baker, D.N. and Belian, R.D.}, title={ The interaction of impulsive solar wind discontinuities with the magnetosphere: a multi-satellite case study }, journal={Planetary and Space Science}, volume={38}, number={7}, year={1990}, month={Jul}, pages={841-50}, abstract={ During the magnetic storm of 4-5 September 1984, the outbound AMPTE/IRM spacecraft stayed just outside the expanding Earth's bow shock for a period of 7.5 h. During this interval the solar wind ram pressure and the interplanetary magnetic field remained approximately constant, except for two distinct impulsive pressure pulses lasting a few minutes each. These pulses coincided with discontinuities in which the IMF changed direction by about 90 degrees , and the solar wind kinetic pressure decreased slightly. Accompanying these discontinuities, the following magnetospheric signatures were observed: (1) immediately after each discontinuity, the growth phase of a substorm commenced as evidenced by decreases in the flux of energetic ions at geosynchronous orbit on both the dayside and nightside; (2) equatorial magnetograms recorded sudden impulses in the magnetic field; and (3) after a delay of 8-12 min, the IRM detected outward motion of the bow shock, and in each case about an hour passed before the outward-moving satellite caught up again with the shock }, keywords={ magnetic storms magnetosphere solar wind Earth solar wind magnetosphere interaction AMPTE AD 1984 09 04 AD 1984 09 05 sudden impulse impulsive solar wind discontinuities magnetic storm bow shock ram pressure interplanetary magnetic field impulsive pressure pulses IMF growth phase substorm }, mynotes={UNREAD}, } @ARTICLE{RossbergApr84, title={ A close look at the solar wind-magnetosphere interaction }, journal={Journal of Geophysical Research}, volume={89}, number={A4}, year={1984}, month={Apr}, pages={3162-8}, abstract={ A study of the short-term (12-hour) variation of the linear correlation between the solar wind-magnetosphere energy coupling function epsilon and the electrojet index AE revealed unexpectedly large variations of the correlation coefficient R and of the ratio between epsilon and AE. About half of all R values fell below the 95% confidence level, and the ratio between epsilon AE and varied by more than 100% of the average value, even when R was large. This result reveals that the epsilon function is not a very good predictor of substorms and their intensities. Several possible causes for the variations are discussed. It is shown that some of the variations of the correlation coefficient occur because of a variable temporal relationship between epsilon and AE }, keywords={ electrojets magnetosphere solar wind solar wind-magnetosphere interaction energy coupling function electrojet index AE substorms }, mynotes={UNREAD}, } @ARTICLE{De-PaterSep77, author={De Pater, I. and Weber, W.J.}, title={ Computations on the interaction of an interplanetary shock with the Earth's magnetosphere }, journal={Astrophysics and Space Science}, volume={51}, number={1}, year={1977}, month={Sep}, pages={217-24}, abstract={ The results of a one-dimensional computer simulation of the interaction between interplanetary and the Earth's magnetosphere are presented. The position of the bowshock as a function of solar wind velocity and interplanetary field direction is studied }, keywords={ geophysics computing interplanetary magnetic fields interplanetary matter magnetosphere shock waves simulation solar wind interplanetary shock magnetosphere solar wind velocity interplanetary field direction Earth bow shock position one dimensional computer simulation }, mynotes={UNREAD}, } @ARTICLE{TamaoAug76, author={Tamao, T. and Ishihara, T.}, title={ Diffusion of trapped particles due to the bounce-drift resonance interaction in the magnetosphere }, journal={Astrophysics and Space Science}, volume={43}, number={1}, year={1976}, month={Aug}, pages={199-211}, abstract={ Within the framework of the quasi-linear approximation, the hybrid diffusion process due to the bounce-drift resonance interaction between trapped particles and low-frequency field fluctuations is examined. The diffusion coefficients obtained, which are valid for particles with large pitch angles, cover the previous results in a few limiting cases. In general, the diffusion coefficients depend strongly on the spatial structure of the power spectrum along field lines, as well as the frequency dependence. The relative importance of the radial diffusion and field-aligned acceleration for ring-current particles is discussed. It is shown that the field-aligned acceleration exceeds the inward penetration of the particles near the plasmapause }, keywords={ diffusion geomagnetism magnetosphere magnetosphere hybrid diffusion process radial diffusion plasmapause trapped particles diffusion ring current particles bounce drift resonance interaction low frequency field fluctuations field lines power spectrum spatial structure large pitch angle particles field aligned acceleration }, mynotes={UNREAD}, } @ARTICLE{NunnNov75, author={Nunn, D. and Helliwell, R.A. and Crystal, T.L.}, title={ Comment on 'A feedback model of cyclotron interaction between whistler mode waves and energetic electrons in the magnetosphere' by R.A. Helliwell and T.L. Crystal }, journal={Journal of Geophysical Research}, volume={80}, number={31}, year={1975}, month={Nov}, pages={4397-400}, abstract={ For original see ibid., vol.78, p.7357 (1973). Examines the theory of the self-consistent nonlinear interaction between a narrow band whistler wave and cyclotron resonant electrons. The calculation of the resonant particle current is discussed in detail. The importance in wave-particle interactions of the inhomogeneity of the background magnetic field is emphasised. The results of the feedback model are compared with the observations by Bell and Helliwell (1971) }, keywords={ atmospheric electromagnetic wave propagation cyclotron resonance feedback magnetosphere radiowave propagation whistlers feedback model cyclotron interaction whistler mode waves energetic electrons magnetosphere narrow band whistler wave cyclotron resonant electrons resonant particle current 10 Hz pulsations self consistent nonlinear interactions wave particle interactions magnetic field inhomogeneity }, mynotes={UNREAD}, } @ARTICLE{ColeJul74, title={ Outline of a theory of solar wind interaction with the magnetosphere }, journal={Planetary and Space Science}, volume={22}, number={7}, year={1974}, month={Jul}, pages={1075-88}, abstract={ Some new ideas on the interaction of the solar wind with the magnetosphere are brought forward. The mechanism of reflection of charged particles at the magnetopause is examined }, keywords={ magnetosphere solar corpuscular radiation solar wind interaction magnetosphere magnetopause electric fields interplanetary magnetic field ionosphere geomagnetic field polar caps geomagnetic tail auroral electrojets charged particle reflection }, mynotes={UNREAD}, } @ARTICLE{KovnerJul73, author={Kovner, M.S. and Feldstein, Y.I.}, title={ On solar wind interaction with the Earth's magnetosphere }, journal={Planetary and Space Science}, volume={21}, number={7}, year={1973}, month={Jul}, pages={1191-211}, abstract={ The initial fact, well established, is that the density of the magnetic field energy in the solar wind is rather small. Magnetic field intensity and orientation are shown to determine the character of the solar wind flow around the magnetosphere. For mean parameters of the wind, if the tangential component of the magnetic field is more or equal 5 gamma , the flow in the magnetosheath will be laminar. For other cases the flow is of a turbulent type. For turbulent flow, typical plasma parameters are estimated: mean free path, internal scale of inhomogeneities and dissipated energy. The results obtained are compared with experimental data. For the case of laminar flow, special attention is paid to the situation when magnetic fields of the solar wind and Earth are antiparallel. It is suggested, on the basis of solid arguments, that the southward interplanetary field diffuses from the magnetosheath into the Earth's magnetosphere. It is shown that during the magnetospheric substorms, relaxation oscillations with the period tau =100-300 sec must appear. A theorem is proved about the appearance of a westward electrical field during the substorm development, when the magnetosphere's day-side boundary moves Earthward and about the recovery phase, when the magnetopause motion is away from the Earth, when there is an eastward electrical field }, keywords={ interplanetary magnetic fields laminar flow magnetosphere solar corpuscular radiation turbulent flow solar wind interaction Earth's magnetosphere magnetosheath turbulent flow plasma laminar flow southward interplanetary field magnetospheric substorms relaxation oscillations }, mynotes={UNREAD}, } @ARTICLE{RigbyMar73, author={Rigby, B.J. and Mainstone, J.S.}, title={ The effect of the Earth's bow shock and magnetosheath on the interaction of a discontinuity in the solar wind with the magnetosphere }, journal={Planetary and Space Science}, volume={21}, number={3}, year={1973}, month={Mar}, pages={499-506}, abstract={ A theoretical model is proposed for the interaction of a plane discontinuity in the solar wind with the magnetosphere. The presence of the bow shock and magnetosheath are taken into account, the calculation being based on the Spreiter et al. (1966) gas-dynamic model for a solar wind Mach Number M=5. The model proposed predicts the manner in which the shape of the interplanetary discontinuity is distorted in its passage through the magnetosheath }, keywords={ magnetosphere solar corpuscular radiation solar wind discontinuity Earth's bow shock magnetosheath magnetosphere Mach Number M=5 }, mynotes={UNREAD}, } @ARTICLE{NishidaApr71, author={Nishida, A. and Maezawa, K.}, title={ Two basic modes of interaction between the solar wind and the magnetosphere }, journal={Journal of Geophysical Research}, volume={76}, number={10}, year={1971}, month={Apr}, pages={2254-64}, abstract={ By using Explorer 33 and 35 interplanetary plasma and magnetic field data, it is confirmed that there are at least two basic modes in the interaction mechanism between the solar wind and the magnetosphere. The first is the change in the magnetospheric dimension that results from changes in the solar wind dynamic pressure exerted at the magnetopause and the second is the fluctuation in the magnetospheric DP 2 electric field that is related to fluctuations in the north-south component of the interplanetary magnetic field. Whereas the first can be interpreted essentially by the classical Chapman-Ferraro theory, the second suggests that the interplanetary electric field penetrates deep into the magnetosphere }, keywords={ magnetosphere solar corpuscular radiation modes interaction mechanism solar wind magnetosphere magnetospheric dimension dynamic pressure magnetopause fluctuation electric field }, mynotes={UNREAD}, } @ARTICLE{KovalevskyJun71, title={ The interplanetary medium and its interaction with the earth's magnetosphere }, journal={Space Science Reviews}, volume={12}, number={2}, year={1971}, month={Jun}, pages={187-257}, abstract={ Reviews the principle results of direct measurements of the plasma and magnetic field by spacecraft close to the Earth (within the heliocentric distance range 0.7-1.5 AU). Gives an interpretation of the results for periods of decrease, minimum and increase of the solar activity. The following problems are discussed: the interplanetary plasma (chemical composition, density, solar wind flow speed, temperature, temporal and spatial variation of these parameters), the interplanetary magnetic field (intensity, direction, fluctuations and its origin), some derived parameters characterizing the physical condition of the interplanetary medium; the quasi-stationary sector structure and its connection with solar and terrestrial phenomena; the magnetohydrodynamic discontinuities in the interplanetary medium (Tangential discontinuities and collisionless shock waves); the solar magnetoplasma interaction with the geomagnetic field (the collisionless bow shock wave, the magnetosheath, the magnetopause, the Earth's magnetic tail, the internal magnetosphere characteristics), the connection between the geomagnetic actitivity and the interplanetary medium and magnetosphere parameters; peculiarities in behaviour of the interplanetary medium and magnetosphere during geomagnetic storms; energetic aspects of the geomagnetic storms }, keywords={ interplanetary matter magnetosphere reviews interplanetary medium interaction Earth's magnetosphere interplanetary magnetic field magnetohydrodynamic discontinuities }, mynotes={UNREAD}, } @ARTICLE{Matsumoto81, author={Matsumoto, H. and Hashimoto, K. and Morikura, M. and Kimura, I. and Mukai, T.}, title={ Correlation between VLF plasma waves and energetic electrons simultaneously observed by satellite JIKIKEN (EXOS-B) }, journal={Journal of Geomagnetism and Geoelectricity}, volume={33}, number={1}, year={1981}, month={}, pages={73-87}, abstract={ Case studies on correlation between VLF plasma waves and energetic electrons are presented. The frequency range of the observed VLF plasma waves is from 150 Hz to 9.5 kHz, while the measured energy range of electrons is from 5 eV to 11 keV. Data observed on four passes are examined. It is shown that band-limited hiss and discrete VLF emissions below a local cyclotron frequency are well correlated with 1 to 10 keV electrons }, keywords={ electrons magnetospheric electromagnetic wave propagation plasma waves magnetosphere VLF plasma waves energetic electrons JIKIKEN (EXOS-B band-limited hiss local cyclotron frequency }, mynotes={UNREAD}, } @ARTICLE{Itonaga97, author={Itonaga, M. and Yoshikawa, A. and Yumoto, K.}, title={ One-dimensional transient response of the inner magnetosphere at the magnetic equator. 2. Analysis of waveforms }, journal={Journal of Geomagnetism and Geoelectricity}, volume={49}, number={1}, year={1997}, month={}, pages={49-68}, abstract={ For pt.1 see ibid., vol.49, no.1, p.21-48 (1997). Under a model of altitude distribution of the Alfven speed V/sub A/, one-dimensional transient response of the inner magnetosphere at the magnetic equator to earthward propagating impulse- and step-like MHD disturbances is considered. The waveforms of transient compressional oscillations due to these disturbances at some L shells are directly simulated by a numerical inversion of the Laplace transform with orthonormal Laguerre functions. The present paper concentrates on the analysis of waveforms. Then, it is verified that the compressional oscillations are due to the poles of the system under consideration. The oscillation arising from the cavity resonance all over the inner magnetosphere is most dominant. However, its amplitude becomes smaller as the characteristic time scale T of an incident disturbance grows large, and it is negligibly small for T greater than several times of eigen-period of the resonance. On the other hand, when T is relatively small (e.g., Tor approximately=70 keV) and electron (E>or approximately=30 keV) observations are presented for three fortuitously positioned geostationary spacecraft during a strong magnetospheric compression event which brought the subsolar magnetopause inward of the synchronous orbit (r=6.6 R/sub E/) on November 1, 1984. Active Magnetospheric Particle Tracer Explorers (AMPTE) Charge Composition Explorer (CCE) field and particle data show that the CCE spacecraft (at r=8.8 R/sub E/) was in the upstream solar wind during the compression event and several upstream particle bursts were observed between 0650 and 0930 UT. Spacecraft 1984-037 near 2200 LT observed multiple, sharp energetic particle injection events indicative of substorm onsets occurring at approximately 0650, 0720, and 0750 UT on November 1. Spacecraft 1981-025 near local noon observed some brief magnetopause encounters as early as 0635 UT, and after 0650 UT it remained near (and often outside) the magnetopause for most of the ensuing 3 hours. Observations of energetic particle fluxes and anisotropies near the noon magnetopause suggest that magnetospheric particles escaped into the dayside magnetosheath }, keywords={ magnetic storms magnetosphere solar wind solar wind magnetosphere interaction simultaneous observation AD 1984 11 01 energetic electron foreshock energetic particle observations geostationary orbit upstream solar wind leakage magnetospheric compression event ion subsolar magnetopause upstream particle bursts substorm onsets magnetosheath }, mynotes={UNREAD}, } @ARTICLE{BakerDec88, author={Baker, D.N. and Belian, R.D. and Fritz, T.A. and Higbie, P.R. and Krimigis, S.M. and Sibeck, D.G. and Zwickl, R.D.}, title={ Simultaneous energetic particle observations at geostationary orbit and in the upstream solar wind: evidence for leakage during the magnetospheric compression event of November 1, 1984 }, journal={Journal of Geophysical Research}, volume={93}, number={A12}, year={1988}, month={Dec}, pages={14317-27, 14735-8}, abstract={ Energetic ion (E>or approximately=70 keV) and electron (E>or approximately=30 keV) observations are presented for three fortuitously positioned geostationary spacecraft during a strong magnetospheric compression event which brought the subsolar magnetopause inward of the synchronous orbit (r=6.6 R/sub E/) on November 1, 1984. Active Magnetospheric Particle Tracer Explorers (AMPTE) Charge Composition Explorer (CCE) field and particle data show that the CCE spacecraft (at r=8.8 R/sub E/) was in the upstream solar wind during the compression event and several upstream particle bursts were observed between 0650 and 0930 UT. Spacecraft 1984-037 near 2200 LT observed multiple, sharp energetic particle injection events indicative of substorm onsets occurring at approximately 0650, 0720, and 0750 UT on November 1. Spacecraft 1981-025 near local noon observed some brief magnetopause encounters as early as 0635 UT, and after 0650 UT it remained near (and often outside) the magnetopause for most of the ensuing 3 hours. Observations of energetic particle fluxes and anisotropies near the noon magnetopause suggest that magnetospheric particles escaped into the dayside magnetosheath }, keywords={ magnetic storms magnetosphere solar wind solar wind magnetosphere interaction simultaneous observation AD 1984 11 01 energetic electron foreshock energetic particle observations geostationary orbit upstream solar wind leakage magnetospheric compression event ion subsolar magnetopause upstream particle bursts substorm onsets magnetosheath }, mynotes={UNREAD}, } @ARTICLE{ShueMay97, author={Shue, J.-H. and Chao, J.K. and Fu, H.C. and Russell, C.T. and Song, P. and Khurana, K.K. and Singer, H.J.}, title={ A new functional form to study the solar wind control of the magnetopause size and shape }, journal={Journal of Geophysical Research}, volume={102}, number={A5}, year={1997}, month={May}, pages={9497-511}, abstract={ In this study a new functional form, r=r/sub 0/ [2/(1+cos theta )]/sup alpha /, is used to fit the size and shape of the magnetopause using crossings from ISEE 1 and 2, Active Magnetospheric Particle Tracer Explorers/Ion Release Module (AMPTE/IRM), and IMP 8 satellites. This functional form has two parameters, r/sub 0/ and alpha , representing the standoff distance and the level of tail flaring. The value r is the radial distance at an angle ( theta ) between the Sun-Earth line and the direction of r. It is found that r/sub 0/ varies with the interplanetary magnetic field (IMF) B/sub z/ component and has a break in the slope at B/sub z/=0 nT. The best-fit value of r/sub 0/ decreases with increasing southward IMF B/sub z/. For northward IMF B/sub z/, the best-fit value of r/sub 0/ increases slightly with increasing B/sub z/. The best-fit value of alpha increases monotonically with decreasing IMF B/sub z/. The dynamic pressure (D/sub p/) also changes r/sub 0/ and alpha . The parameters D/sub p/ and r/sub 0/ are related by a power law of -1/(6.6+or-0.8). The best-fit value of alpha is slightly larger for larger dynamic pressure, which implies that D/sub p/ also has a role in flux transfer from the dayside to the nightside, but the size of this effect is small. An explicit function for the size and shape of the magnetopause, in terms of D/sub p/ and B/sub z/, is obtained by using multiple parameter fitting in a form that is useful for operational space applications such as predicting when satellites at geosynchronous orbit will be found in the magnetosheath }, keywords={ magnetosphere solar wind solar wind magnetosphere interaction functional form theory solar wind control magnetopause size morphology shape ISEE 1 ISEE 2 AMPTE IRM IMP 8 dynamic pressure flux transfer }, mynotes={UNREAD}, } @ARTICLE{LinFeb95, author={Lin, R.P. and Anderson, K.A. and Ashford, S. and Carlson, C. and Curtis, D. and Ergun, R. and Larson, D. and McFadden, J. and McCarthy, M. and Parks, G.K. and Reme, H. and Bosqued, J.M. and Coutelier, J. and Cotin, E. and D'Uston, C. and Wenzel, K.-P. and Sanderson, T.R. and Henrion, J. and Ronnet, J.C. and Paschmann, G.}, title={ A three-dimensional plasma and energetic particle investigation for the WIND spacecraft }, journal={Space Science Reviews}, volume={71}, number={1-4}, year={1995}, month={Feb}, pages={125-53}, abstract={ This instrument is designed to make measurements of the full three-dimensional distribution of suprathermal electrons and ions from solar wind plasma to low energy cosmic rays, with high sensitivity, wide dynamic range, good energy and angular resolution, and high time resolution. The primary scientific goals are to explore the suprathermal particle population between the solar wind and low energy cosmic rays, to study particle acceleration and transport and wave-particle interactions, and to monitor particle input to and output from the Earth's magnetosphere. Three arrays, each consisting of a pair of double-ended semi-conductor telescopes each with two or three closely sandwiched passivated ion implanted silicon detectors, measure electrons and ions above approximately 20 keV. One side of each telescope is covered with a thin foil which absorbs ions below 400 keV, while on the other side the incoming <400 keV electrons are swept away by a magnet so electrons and ions are cleanly separated. Higher energy electrons (up to approximately 1 MeV) and ions (up to 11 MeV) are identified by the two double-ended telescopes which have a third detector. The telescopes provide energy resolution of Delta E/E approximately=0.3 and angular resolution of 22.5 degrees *36 degrees , and full 4 pi steradian coverage in one spin (3 s). Top-hat symmetrical spherical section electrostatic analyzers with microchannel plate detectors are used to measure ions and electrons from approximately 3 eV to 30 keV. All these analyzers have either 180 degrees or 360 degrees fields of view in a plane, Delta E/E approximately=0.2, and angular resolution varying from 5.6 degrees (near the ecliptic) to 22.5 degrees }, keywords={ artificial satellites astronomical instruments astrophysical plasma atmospheric measuring apparatus cosmic ray electrons cosmic ray nuclei magnetosphere solar cosmic ray particles solar wind plasma investigation energetic particle investigation WIND spacecraft three-dimensional distribution suprathermal electrons suprathermal ions cosmic rays acceleration transport wave-particle interactions magnetosphere double-ended semi-conductor telescopes closely sandwiched passivated ion implanted Si detectors energy resolution angular resolution top-hat symmetrical spherical section electrostatic analyzers microchannel plate detectors 3 eV to 11 MeV Si }, mynotes={UNREAD}, } @ARTICLE{BellSep93, author={Bell, T.F. and Helliwell, R.A. and Inan, U.S. and Lauben, D.S.}, title={ The heating of suprathermal ions above thunderstorm cells }, journal={Geophysical Research Letters}, volume={20}, number={18}, year={1993}, month={Sep}, pages={1991-4}, abstract={ Ion heating in the topside ionosphere directly over thunderstorm cells is estimated. The primary heating is due to lower hybrid waves excited through linear mode coupling as intense electromagnetic (EM) whistler mode radiation from lightning is scattered from small scale (2-20 m) magnetic-field-aligned plasma density irregularities in the topside ionosphere. For typical radiated EM fields, it was found that suprathermal H/sup +/ ions in the >or=6 eV energy range can be heated by 20 to 40 eV as a result of a single lightning discharge. They also show how the number density of >or=6 eV H/sup +/ ions is enhanced by preheating resulting from the absorption of proton whistlers in the 500-1000 km altitude range. For lightning discharge rates of one or more per second over a 10/sup 4/ km/sup 2/ area, the authors' model predicts a total energy gain for the H/sup +/ ions of 400 eV to 2 KeV and a perpendicular ion flux of j/sub perpendicular to / approximately 10/sup 5/ to 10/sup 6/ cm/sup -2/ sec/sup -1/. These fluxes should be observable on low altitude spacecraft using presently available instrumentation }, keywords={ ionosphere ionospheric electromagnetic wave propagation thunderstorms whistlers ion heating lower atmosphere meteorology plasma wave radiowave suprathermal ions thunderstorm cells topside ionosphere lower hybrid waves linear mode coupling intense electromagnetic whistler mode radiation lightning field-aligned plasma density irregularities H/sup +/ whistlers 500 to 1000 km H }, mynotes={UNREAD}, } @ARTICLE{BellApr86, title={ The wave magnetic field amplitude threshold for nonlinear trapping of energetic gyroresonant and Landau resonant electrons by nonducted VLF waves in the magnetosphere }, journal={Journal of Geophysical Research}, volume={91}, number={A4}, year={1986}, month={Apr}, pages={4365-79}, abstract={ Using a recently developed theory, the author calculates the wave magnetic field amplitude threshold B/sub tau / necessary to allow the nonlinear trapping of energetic gyroresonant and Landau resonant electrons by VLF whistler mode waves in the magnetosphere, propagating at an arbitrary angle, psi , with respect to the Earth's magnetic field, B/sub 0/. This theory predicts that the amplitude threshold is governed near the magnetic equatorial plane by the gradient of psi with respect to distance, z, along B/sub 0/. Using commonly accepted models of the magnetosphere and computer ray-tracing techniques, the function psi (z) is calculated for magnetic shells in the range 2or approximately=100 keV) auroral particle precipitation. When the region of auroral particle precipitation passes over a VLF propagation path, disturbances in the D-region of the ionosphere created by the high-energy particles perturb the amplitude of VLF signals propagating below in a characteristic manner. Continuous nighttime observations of the amplitude of the signal from the NLK transmitter (24.8 kHz, Jim Creek, Washington) were made in Gander, Newfoundland, during November 1993 and January 1994. Simultaneous images of atmospheric X-rays created by auroral particle precipitation taken by the AXIS instrument on the UARS satellite were examined for times when large-scale auroral particle precipitation extended over the NLK-Gander propagation path. Quantitative characteristics of the precipitation-associated NLK signal perturbations are established from days which clearly exhibit good correlation between the AXIS images and VLF data, and a larger data set from the months of November 1993 and January 1994 is examined statistically to determine the effectiveness of the VLF technique in capturing particle precipitation events. The number of particle precipitation onsets seen in the AXIS images that can be readily identified in the VLF amplitude data is found to be almost 94%. VLF propagation model calculations show that the observed VLF amplitude decreases are consistent with propagation under conditions of enhanced lower ionosphere electron density caused by auroral electron precipitation and suggest that electrons with energies greater than 100 keV are responsible for the VLF amplitude perturbations }, keywords={ atmospheric electron precipitation atmospheric ion precipitation ionospheric techniques ionosphere measurement technique radiowave propagation VLF remote sensing high-energy auroral particle precipitation electron precipitation VLF transmitter signal Earth-ionosphere waveguide location nighttime high-energy precipitation D-region NLK transmitter USA Washington Newfoundland Canada Gander AD 1993 AD 1994 signal perturbation VLF technique ion precipitation 24.8 kHz }, mynotes={UNREAD}, } @ARTICLE{InanMay96, author={Inan, U.S. and Pasko, V.P. and Bell, T.F.}, title={ Sustained heating of the ionosphere above thunderstorms as evidenced in "early/fast" VLF events }, journal={Geophysical Research Letters}, volume={23}, number={10}, year={1996}, month={May}, pages={1067-70}, abstract={ Quasi-electrostatic (QE) thundercloud fields are proposed to maintain the ionospheric electrons at a persistently heated level well above their ambient thermal energy. Changes in the thundercloud charge (e.g., in lightning discharges) lead to heating/cooling above/below this quiescent level, and are registered as sudden (i.e., fast'<20 ms) subionospheric VLF signal changes, occurring simultaneously (i.e., early'<20 ms) with lightning discharges, and referred to as early/fast VLF events [Inan et al., 1993] }, keywords={ atmospheric radiation atmospheric temperature ionospheric disturbances lightning thunderstorms sustained heating ionosphere thunderstorms VLF events quasi-electrostatic thundercloud fields lightning discharges cooling subionospheric VLF signal changes }, mynotes={UNREAD}, } @ARTICLE{JasnaJun94, author={Jasna, D. and Inan, U.S. and Bell, T.F.}, title={ Precipitation of radiation belt electrons by magnetospherically reflected (MR) whistlers }, journal={Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika}, volume={37}, number={6}, year={1994}, month={Jun}, pages={727-40}, abstract={ Uses a test particle simulation model based on gyro-averaged equations of motion to study the influence of oblique magnetospherically reflected (MR) whistlers on the near-loss-cone distribution function of radiation belt electrons. The authors find that MR whistlers originating in lightning can resonantly interact with radiation belt electrons over a broad range of L-shells and precipitate higher energy electrons from lower L-shells. Electrons in the energy range of 1-2.6 Me V are precipitated from L=2, whereas from L=4 the precipitated electron energy range is 150-220 keV. The precipitated differential electron flux due to this interaction is higher for higher L-shells, and the maximum value ranges from Phi /sub E(prec)/(1.11 MeV)=5.2*10/sup -4/ el/cm/sup 2/.s.keV at L=2 to Phi /sub E(prec)/(173 keV)=4.6*10/sup -1/ el/cm/sup 2/.s.keV at L=4. The lifetimes of radiation belt electrons in a given magnetic flux tube around the L-shell on which the interaction takes place are found to be of the order of several days, comparable to lifetimes corresponding to electron loss induced by hiss, which was heretofore assumed to be the dominant loss mechanism. The minimum electron lifetimes vary from 2.47 days for E=1.11 MeV electrons at L=2 to 4.64 days for E=173 keV electrons at L=4 }, keywords={ atmospheric electron precipitation radiation belts whistlers radiation belt electrons magnetospherically reflected whistlers test particle simulation model gyro-averaged equations of motion near-loss-cone distribution function precipitation L-shells precipitated differential electron flux magnetic flux tube electron loss hiss loss mechanism minimum electron lifetimes 1 to 2.6 MeV 150 to 220 keV }, mynotes={UNREAD}, } @ARTICLE{Lev-TovNov95, author={Lev-Tov, S.J. and Inan, U.S. and Bell, T.F.}, title={ Altitude profiles of localized D region density disturbances produced in lightning-induced electron precipitation events }, journal={Journal of Geophysical Research}, volume={100}, number={A11}, year={1995}, month={Nov}, pages={21375-83}, abstract={ A three-dimensional model of very low frequency (VLF) radio wave propagation in the Earth-ionosphere waveguide in the presence of lower ionospheric disturbances is used to quantitatively interpret VLF signatures of lightning-induced electron precipitation (LEP) events observed in two previously reported cases. One case is that of a 28.5-kHz signal originating in Puerto Rico and propagating to a receiver in Lake Mistissini, Quebec. The other case involves a 24.0-kHz signal originating in Cutler, Maine, and received at Stanford, California. In both cases, high-resolution measurements of the VLF signals were made to accurately document characteristic signatures of LEP events. The comparison of the model calculations with the data yields information about the altitude profiles of electron density of both the extra ionization produced by the LEP events and of the ambient ionospheric D-region. The comparisons are carried out using generally accepted values of the spatial extent of the disturbed regions and the intensity of the particle flux constituting the LEP burst }, keywords={ atmospheric electron precipitation D-region Earth-ionosphere waveguide electron density ionospheric disturbances lightning radiowave propagation ionosphere localized D-region density disturbances lightning-induced electron precipitation events altitude profiles 3D model VLF radio wave propagation Earth-ionosphere waveguide lower ionospheric disturbances high-resolution measurements LEP events electron density ionization disturbed regions particle flux intensity 28.5 kHz 24 kHz }, mynotes={UNREAD}, } @ARTICLE{BellNov95, author={Bell, T.F. and Inan, U.S. and Danielson, M.T. and Cummer, S.A.}, title={ VLF signatures of ionospheric heating by HIPAS }, journal={Radio Science}, volume={30}, number={6}, year={1995}, month={Nov}, pages={1855-67}, abstract={ The amplitude and phase of subionospherically propagating VLF signals are known to be sensitive indicators of the electron density and temperature at D region altitudes. The authors present new observations at a station in Alaska positioned to provide measurements of VLF signals that have propagated beneath the ionospheric region heated by the high-power auroral stimulation (HIPAS) HF heating facility near Fairbanks, Alaska. Analysis of data from HIPAS campaigns conducted in fall 1992 and spring 1993 has shown that in roughly 60% of the cases analyzed, the amplitude of the 23.4-kHz signal from the NPM transmitter in Hawaii as observed in Fort Yukon, Alaska, exhibited a measurable change in amplitude with the same on/off modulation pattern as that of the HIPAS HF transmissions at 2.85 MHz. In almost 70% of the cases analyzed, the same signal exhibited similar measurable changes in phase. The amplitude changes ranged from -0.2 dB to +0.5 dB, and the sensitivity of the measurement was approximately +or-0.02 dB. The phase changes ranged from -4.5 degrees to -0.3 degrees , and the sensitivity of the measurement was typically +or-0.4 degrees . It is demonstrated that the phase and amplitude changes can be used as diagnostic tools to determine characteristics of the ambient electron density profile above the HIPAS facility }, keywords={ D-region electron density ionospheric disturbances ionospheric electromagnetic wave propagation radiowave propagation ionospheric heating VLF signatures amplitude phase subionospherically propagating VLF signals electron density temperature D region HIPAS high-power auroral stimulation HF heating facility on/off modulation pattern AD 1992 to 1993 23.4 kHz 2.85 MHz }, mynotes={UNREAD}, } @ARTICLE{RodriguezDec94, author={Rodriguez, J.V. and Inan, U.S. and Bell, T.F.}, title={ Heating of the nighttime D region by very low frequency transmitters }, journal={Journal of Geophysical Research}, volume={99}, number={A12}, year={1994}, month={Dec}, pages={23329-38}, abstract={ VLF signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D-region over three U.S. Navy very low frequency (VLF, 3-30 kHz) transmitters. Ionospheric cooling and heating are observed when a transmitter turns off and on in the course of normal operations. Heating by the 24.0-kHz NAA transmitter in Cutler, Maine, (1000 kW radiated power) was observed by this method in 41 of 52 off/on episodes during December 1992, increasing the amplitude and retarding the phase of the 21.4-kHz NSS probe wave propagating from Annapolis, Maryland, to Gander, Newfoundland, by as much as 0.84 dB and 5.3 degrees , respectively. In six of these 41 episodes, the amplitude of the 28.5-kHz NAU probe wave propagating from Puerto Rico to Gander was also perturbed by as much as 0.29 dB. The latter observations were unexpected due to the >770 km distance between NAA and the NAU-Gander great circle path. Heating by the NSS (21.4 kHz, 265 kW) and NLK (24.8 kHz, 850 kW) transmitters was observed serendipitously in data from earlier measurements of the amplitudes of VLF signals propagating in the Earth-ionosphere waveguide. A three-dimensional model of wave absorption and electron heating in a magnetized, weakly ionized plasma is used to calculate the extent and shape of the collision frequency (i.e. electron temperature) enhancement above a VLF transmitter. The calculated changes in the D-region conductivity are used in a three-dimensional model of propagation in the Earth-ionosphere waveguide to predict the effect of the heated patch on a subionospheric VLF probe wave }, keywords={ D-region Earth-ionosphere waveguide ionospheric disturbances plasma radiofrequency heating radiowave propagation heated nighttime D-region Earth-ionosphere waveguide VLF signals ionospheric cooling ionospheric heating NAA transmitter NSS probe wave NAU probe wave NSS transmitter NLK transmitter 3D propagation model wave absorption electron heating magnetized weakly ionized plasma collision frequency electron temperature enhancement D-region conductivity subionospheric VLF probe wave 24 kHz 21.4 kHz 28.5 kHz 24.8 kHz }, mynotes={UNREAD}, } @ARTICLE{Jasna93, author={Jasna, D. and Inan, U.S. and Bell, T.F.}, title={ Resonant interactions between radiation belt electrons and whistler mode waves in the magnetosphere }, journal={Publications of the Faculty of Electrical Engineering, Series: EngineeringPhysics}, volume={}, number={}, year={1993}, month={}, pages={49-66}, abstract={ A computer simulation model is developed to study the interaction between relativistic charged particles and whistler mode waves traveling obliquely with respect to the ambient magnetic field. The authors use this test particle simulation model based on gyro-averaged equations of motion to study the influence of oblique magnetospherically reflected (MR) whistlers on the near-loss-cone distribution function of radiation belt electrons. The authors find that MR whistlers originating in lightning can resonantly interact with radiation belt electrons over a broad range of L-shells and precipitate higher energy electrons from lower L-shells. Electrons in the energy range of 1-26 MeV are precipitated from L=2, whereas from L=4 the precipitated electron energy range is 150-220 keV. The precipitated differential electron flux, due to this interaction, is higher for higher L-shells, and the maximum value ranges from Phi /sub Eprec/(1.11 MeV)=5.2*10/sup -4/ el/cm/sup 2/.s.keV at L=2 to Phi /sub Eprec/(173 keV)=4.6*10/sup -1/ el/cm/sup 2/.s.keV at L=4. The lifetimes of radiation belt electrons in a given magnetic flux tube around the L-shell on which the interaction takes place are found to be of the order of several days, comparable to lifetimes corresponding to electron loss induced by hiss, which was heretofore assumed to be the dominant loss mechanism. The minimum electron lifetimes vary from 2.47 days for E=1.11 MeV electrons at L=2 to 4.64 days for E=173 keV electrons at L=4 }, keywords={ atmospheric electron precipitation electromagnetic waves radiation belts whistlers resonant interaction radiation belt electrons whistler mode waves magnetosphere particle sources loss processes dynamic equilibrium pitch angle energetic electrons computer simulation model relativistic charged particles ambient magnetic field oblique magnetospherically reflected whistlers loss-cone distribution L-shells electron precipitation radiation belt electron lifetimes magnetic flux tube electron loss 150 keV to 2.6 MeV }, mynotes={UNREAD}, } @ARTICLE{TaranenkoDec93, author={Taranenko, Y.N. and Inan, U.S. and Bell, T.F.}, title={ The interaction with the lower ionosphere of electromagnetic pulses from lightning: excitation of optical emissions }, journal={Geophysical Research Letters}, volume={20}, number={23}, year={1993}, month={Dec}, pages={2675-8}, abstract={ A self consistent and fully kinetic simulation of the interaction of lightning radiated electromagnetic (EM) pulses with the nighttime lower ionosphere indicates that optical emissions observable with conventional instruments would be excited. For example, emissions of the 1st and 2nd positive bands of N/sub 2/ occur at rates reaching 7*10/sup 7/ and 10/sup 7/ cm/sup -3/ s/sup -1/ respectively at approximately 92 km altitude for a lightning discharge with an electric field E/sub 100/=20 V/m (normalized to a 100 km distance). The maximum height integrated intensities of these emissions are 4*10/sup 7/ and 6*10/sup 6/ R respectively lasting for approximately 50 mu s }, keywords={ atmospherics D-region lightning nightglow nitrogen plasma thermosphere lower ionosphere electromagnetic pulses lightning optical emissions excitation kinetic simulation nighttime 2nd positive band 1st positive band electric field maximum height integrated intensities 92 km N/sub 2/ }, mynotes={UNREAD}, } @ARTICLE{BellSep93, author={Bell, T.F. and Helliwell, R.A. and Inan, U.S. and Lauben, D.S.}, title={ The heating of suprathermal ions above thunderstorm cells }, journal={Geophysical Research Letters}, volume={20}, number={18}, year={1993}, month={Sep}, pages={1991-4}, abstract={ Ion heating in the topside ionosphere directly over thunderstorm cells is estimated. The primary heating is due to lower hybrid waves excited through linear mode coupling as intense electromagnetic (EM) whistler mode radiation from lightning is scattered from small scale (2-20 m) magnetic-field-aligned plasma density irregularities in the topside ionosphere. For typical radiated EM fields, it was found that suprathermal H/sup +/ ions in the >or=6 eV energy range can be heated by 20 to 40 eV as a result of a single lightning discharge. They also show how the number density of >or=6 eV H/sup +/ ions is enhanced by preheating resulting from the absorption of proton whistlers in the 500-1000 km altitude range. For lightning discharge rates of one or more per second over a 10/sup 4/ km/sup 2/ area, the authors' model predicts a total energy gain for the H/sup +/ ions of 400 eV to 2 KeV and a perpendicular ion flux of j/sub perpendicular to / approximately 10/sup 5/ to 10/sup 6/ cm/sup -2/ sec/sup -1/. These fluxes should be observable on low altitude spacecraft using presently available instrumentation }, keywords={ ionosphere ionospheric electromagnetic wave propagation thunderstorms whistlers ion heating lower atmosphere meteorology plasma wave radiowave suprathermal ions thunderstorm cells topside ionosphere lower hybrid waves linear mode coupling intense electromagnetic whistler mode radiation lightning field-aligned plasma density irregularities H/sup +/ whistlers 500 to 1000 km H }, mynotes={UNREAD}, } @ARTICLE{PoulsenSep93, author={Poulsen, W.L. and Bell, T.F. and Inan, U.S.}, title={ The scattering of VLF waves by localized ionospheric disturbances produced by lightning-induced electron precipitation }, journal={Journal of Geophysical Research}, volume={98}, number={A9}, year={1993}, month={Sep}, pages={15553-9}, abstract={ A 3D model of the scattering of VLF waves in the Earth-ionosphere waveguide by localized disturbances in the lower ionosphere is examined for typical disturbances expected to be produced by lightning-induced electron precipitation events. Results indicate that the scattering is generally independent of the conductivity and permittivity of the Earth's surface immediately beneath the disturbed region except for extremely low conductivities such as that found over deep ice caps. Thus the scattered signal is principally a function of the ionospheric perturbation. For typical disturbances characterized by altitude profiles of enhanced ionization expected for 1.4or=20 V/m may create electron density enhancements >or=10% of ambient. A E/sub 100/=20 V/m pulse from a horizontal radiator at 5 km altitude (e.g. the cloud discharge at the stepped-leader onset) increases the electron temperature by a factor of approximately 400 maximum and the electron density (in one ionization cycle) by approximately 230 cm/sup 3/ maximum; the widths at half-maximum of the heated and ionized regions are 200 km and 90 km. A E/sub 100/=40 V/m pulse from a vertical radiator at 0 km altitude (e.g. the vertical return stroke channel) increases the electron temperature by a factor of approximately 350 maximum and the electron density by approximately 80 cm/sup 3/ maximum }, keywords={ D-region lightning electron heating modification EM pulse EM radiation disturbance radiowave emission D-region ionosphere electromagnetic pulses lightning electron temperature }, mynotes={UNREAD}, } @ARTICLE{TaranenkoSep92, author={Taranenko, Y.N. and Inan, U.S. and Bell, T.F.}, title={ Optical signatures of lightning-induced heating of the D region }, journal={Geophysical Research Letters}, volume={19}, number={18}, year={1992}, month={Sep}, pages={1815-18}, abstract={ Lightning-induced heating of the nighttime D region leads to the excitation of a number of lines of O, O/sub 2/, N/sub 2/, O/sub 2//sup +/, and N/sub 2//sup +/, at intensities of 10-10/sup 9/ rayleighs (R) for vertical observations. For example, the 5577 AA emission from O has intensity approximately 60 R lasting for approximately 350 ms while the 1st and 2nd positive bands of N/sub 2/ are at approximately 10/sup 9/ R but last only approximately 50 mu s }, keywords={ airglow D-region lightning plasma heating visible D-region ionosphere airglow lightning-induced heating O O/sub 2/ N/sub 2/ O/sub 2//sup +/ N/sub 2//sup +/ }, mynotes={UNREAD}, } @ARTICLE{JasnaAug92, author={Jasna, D. and Inan, U.S. and Bell, T.F.}, title={ Precipitation of suprathermal (100 eV) electrons by oblique whistler waves }, journal={Geophysical Research Letters}, volume={19}, number={16}, year={1992}, month={Aug}, pages={1639-42}, abstract={ Electron precipitation induced by oblique whistler waves is investigated using a new test particle simulation code based on gyro-averaged equations of motion. The results indicate that highly oblique waves can efficiently pitch angle scatter suprathermal electrons (10-100 eV). At L=3, for example, in a single encounter with a wave with power density S approximately 8 pW/m/sup 2/ propagating at psi =60 degrees with respect to the Earth's magnetic field B/sub 0/, the average pitch angle scattering of 100 eV electrons is approximately 0.1 degrees . In comparison, the average scattering of energetic (100 keV) electrons by a parallel propagating wave with the same S is approximately 0.01 degrees . Estimates indicate that the precipitated electron energy fluxes resulting from the interaction of approximately 100 eV electrons with oblique waves can be up to 30 times larger than that due to the precipitation of 100 keV electrons by parallel propagating waves }, keywords={ atmospheric electron precipitation magnetosphere magnetospheric electromagnetic wave propagation plasma radiation belts whistlers radiation belt electrons VLF magnetosphere suprathermal electrons precipitation wave-particle interactions wave propagation direction whistler wave power density oblique whistler waves test particle simulation code gyro-averaged equations of motion highly oblique waves average pitch angle scattering precipitated electron energy fluxes 100 eV 10 to 25 kHz 5.60 to 15.79 kHz }, mynotes={UNREAD}, } @ARTICLE{DraganovFeb92, author={Draganov, A.B. and Inan, U.S. and Sonwalkar, V.S. and Bell, T.F.}, title={ Magnetospherically reflected whistlers as a source of plasmaspheric hiss }, journal={Geophysical Research Letters}, volume={19}, number={3}, year={1992}, month={Feb}, pages={233-6}, abstract={ Ray-tracing simulations and estimates of whistler wave damping show that magnetospherically reflected whistlers can persist for approximately 10/sup 2/ s in a low frequency band (f approximately 1 kHz). The combined contribution from whistler rays produced by a single lightning flash but entering the magnetosphere at different points form a continuous hiss-like signal, as observed at a fixed point. Estimates indicate that the total whistler wave energy input into the magnetosphere from lightning discharges may maintain experimentally observed levels of magnetospheric hiss }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation whistlers magnetosphere plasmasphere radiowave emission ELF whistler reflection reflected whistlers hiss whistler wave damping lightning magnetosphere 1 kHz }, mynotes={UNREAD}, } @ARTICLE{TaranenkoJan92, author={Taranenko, Y.N. and Inan, U.S. and Bell, T.F.}, title={ VLF-HF heating of the lower ionosphere and ELF wave generation }, journal={Geophysical Research Letters}, volume={19}, number={1}, year={1992}, month={Jan}, pages={61-4}, abstract={ For incident wave power densities of 10/sup -6/-10/sup -2/ W/m/sup 2/ (at 30 km altitude), VLF heating of the D-region (<90 km) is found to be 2-10 times more effective (depending on power) than HF heating, resulting in comparable perturbations of subionospheric VLF probe waves in spite of up to 10/sup 3/ times larger power density utilized in HF heating and at least as efficient in ELF wave generation. In view of generally larger (100*100 km) areas of the ionosphere illuminated by VLF transmitters, ELF wave generation by modulated VLF heating is estimated to produce ELF power levels of approximately 100 mW, comparable with or larger than those produced in typical HF heating experiments. ELF wave generation in a typical midlatitude ambient ionosphere occurs primarily via the modulation of Pedersen current whereas in a typical auroral ionosphere Hall current is dominant for pump wave frequencies up to approximately 6 MHz. For 10-30 MHz and power densities >10/sup -4/ W/m/sup 2/, Pedersen current modulation is again dominant, potentially providing up to 2-15 times higher ELF dipole moment than those found in experiments using 3-5 MHz heaters }, keywords={ ionospheric electromagnetic wave propagation plasma radiofrequency heating radiowave propagation radiowave absorption lower ionosphere ELF wave generation power densities VLF heating D-region HF heating perturbations heating experiments Pedersen current auroral ionosphere Hall current pump wave frequencies modulation dipole moment 30 to 150 km }, mynotes={UNREAD}, } @ARTICLE{InanApr91, author={Inan, U.S. and Bell, T.F. and Rodriguez, J.V.}, title={ Heating and ionization of the lower ionosphere by lightning }, journal={Geophysical Research Letters}, volume={18}, number={4}, year={1991}, month={Apr}, pages={705-8}, abstract={ Nighttime ionospheric electrons at 90-95 km altitude are heated by a factor of 100-500 during the upward passage of short (<100 mu s) pulses of intense (5-20 V/m at 100 km distance) electromagnetic radiation from lightning. Heated electrons with average energy of 4-20 eV in turn produce secondary ionization, of up to 400 cm/sup -3/ at approximately 95 km altitude in a single ionization cycle ( approximately 3 mu s). With the time constant of heating being 5-10 mu s, a number of such ionization cycles can occur during a 50 mu s radiation pulse, leading to even higher density enhancements. This effect can account for observations of 'early' or 'fast' subionospheric VLF perturbations }, keywords={ atmospheric ionisation atmospheric radiation atmospheric temperature atmospheric thermodynamics D-region electron density ionosphere ionospheric electromagnetic wave propagation lightning nighttime ionospheric electrons heating aeronomy short intense EM radiation pulses ionosphere ionisation D-region ionisation hot electrons energy ionisation cycle time EM pulse duration ionosphere heating time constant fast VLF perturbations ionisation bubbles lower ionosphere lightning secondary ionization single ionization cycle density enhancements subionospheric VLF perturbations 90 to 95 km 3000 ns 100 km 5 to 10 mus 50 mus 4 to 20 eV }, mynotes={UNREAD}, } @ARTICLE{InanJan91, author={Inan, U.S. and Bell, T.F.}, title={ Pitch angle scattering of energetic particles by oblique whistler waves }, journal={Geophysical Research Letters}, volume={18}, number={1}, year={1991}, month={Jan}, pages={49-52}, abstract={ First order cyclotron or Landau resonant pitch angle scattering of electrons by oblique whistler waves propagating at large angles to the ambient field are found to be at least as large as that due to parallel propagating waves. Commonly observed precipitation of >40 keV electrons in association with ducted whistlers may thus be accompanied by substantial fluxes of lower energy (10 eV-40 keV) electrons precipitated by the nonducted components }, keywords={ atmospheric electron precipitation magnetosphere radiation belts EM wave radiowave electron precipitation radiation belt loss process magnetosphere wave particle interaction first order cyclotron energetic particles oblique whistler waves Landau resonant pitch angle scattering }, mynotes={UNREAD}, } @ARTICLE{JasnaOct90, author={Jasna, D. and Inan, U.S. and Bell, T.F.}, title={ Equatorial gyroresonance between electrons and magnetospherically reflected whistlers }, journal={Geophysical Research Letters}, volume={17}, number={11}, year={1990}, month={Oct}, pages={1865-8}, abstract={ Magnetospherically reflected whistlers resonantly interact with energetic (of order 100 keV) electrons in a relatively narrow energy range during multiple equatorial crossings over a wide range of L-shells (1.51). However, the earlier model with fixed n/sub 0/=1 is an excellent approximation whatever linear or saturated state is considered. The efficiency dependence of a CARM amplifier on some basic operating parameters was reexamined by the modified formulations }, keywords={ amplifiers cyclotron masers digital simulation modified self-consistent nonlinear simulation cyclotron autoresonance maser amplifiers wave refractive index modified self-consistent one-dimensional nonlinear model evolving wave refractive index second-order terms azimuthal bunching region axial bunching region linear gain saturated efficiency fast wave branch slow wave branch linear state saturated state operating parameters efficiency dependence }, mynotes={UNREAD}, } @ARTICLE{LawsonOct97, author={Lawson, W. and Fernandez, A. and Hutchings, T. and Saraph, G.P.}, title={ A novel hybrid slow-wave/fast-wave traveling-wave amplifier }, journal={IEEE Transactions on Plasma Science}, volume={25}, number={5}, year={1997}, month={Oct}, pages={1150-4}, abstract={ We introduce a new broad-band amplifier configuration which contains elements of both linear and cyclotron resonance maser microwave tubes. A helix slow-wave structure is used to bunch a linearly streaming annular electron beam. A nonadiabatic magnetic transition, which is placed after a drift region at the point where the ac beam current is nearly maximized, converts much of the beam's axial momentum to rotational momentum. The beam then travels through a tapered right-circular waveguide, where microwave energy is extracted via the gyrotron interaction. The design of a proof-of-principle X-band amplifier is given, and the codes that are used in the simulation are described. The nominal beam voltage and current are 45 kV and 8 A, respectively. The tube is predicted to be stable, to possess a peak efficiency above 43%, and to have an instantaneous bandwidth of over 9% }, keywords={ cyclotron masers masers microwave tubes relativistic electron beam tubes slow wave structures travelling wave amplifiers hybrid slow-wave/fast-wave traveling-wave amplifier broad-band amplifier configuration cyclotron resonance maser microwave tubes helix slow-wave structure linearly streaming annular electron beam nonadiabatic magnetic transition drift region AC beam current axial momentum rotational momentum tapered right-circular waveguide gyrotron interaction microwave energy X-band amplifier 45 kV 8 A 43 percent }, mynotes={UNREAD}, } @ARTICLE{WillesJul97, author={Willes, A.J. and Robinson, P.A.}, title={ Electron-cyclotron maser theory for extraordinary Bernstein waves }, journal={Journal of Plasma Physics}, volume={58}, number={}, year={1997}, month={Jul}, pages={171-91}, abstract={ Electron-cyclotron maser emission is investigated in the regime where wave growth in the electrostatic Bernstein modes dominates ( omega /sub p// Omega /sub e/>1.5). A semirelativistic growth rate is derived assuming that the wave dispersion is dominated by a cool background electron distribution and the instability is driven by a low-density hot loss-cone-like electron distribution. The properties of Bernstein wave growth are most strongly dependent on the relative temperatures of the hot and cool electron distributions. For T/sub hot//T/sub cool/>or approximately=10, the fastest growing Bernstein waves are produced at frequencies just below each cyclotron harmonic in Bernstein modes lying below the upper-hybrid frequency T/sub hot//T/sub cool/0, has been invoked to explain many aspects, such as the modes of propagation, harmonic emissions, and the source characteristics of the auroral kilometric radiation (AKR). Satellite observations of AKR sources indicate that the source regions are often imbedded within the auroral acceleration region characterized by the presence of a field-aligned potential drop. The authors investigate the excitation of the fundamental extraordinary mode radiation due to the accelerated electrons. The momentum space distribution of these energetic electrons is modeled by a realistic upward loss cone as modified by the presence of a parallel potential drop below the observation point. On the basis of linear growth rate calculations the authors present the emission characteristics, such as the frequency spectrum and the emission angular distribution as functions of the plasma parameters. The authors discuss the implication of their results on the generation of the AKR from the edges of the auroral density cavities }, keywords={ electrons magnetospheric electromagnetic wave propagation HF EM wave excitation energetic electrons loss cone distribution field-aligned potential drop electron cyclotron maser instability momentum space anisotropy auroral kilometric radiation source regions auroral acceleration region fundamental extraordinary mode excitation accelerated electrons loss cone emission characteristics auroral density cavities magnetosphere }, mynotes={UNREAD}, } @ARTICLE{WillesFeb94, author={Willes, A.J. and Robinsons, P.A.}, title={ Electron-cyclotron maser emission from streaming distributions }, journal={Journal of Plasma Physics}, volume={51}, number={}, year={1994}, month={Feb}, pages={75-93}, abstract={ Motivated by the need to explain observed elliptically polarized emission from Jupiter, the mechanism of electron-cyclotron maser emission is considered for drifting electron distributions, where the electrons stream with a non-zero mean velocity parallel to the magnetic field lines. An analytical expression for the semirelativistic growth rate is derived and its properties analysed in detail for waves generated in the magneto-ionic modes. The main features of the growth rate are discussed, on the basis of a geometric analysis using resonant ellipses }, keywords={ astronomical masers astrophysical plasma astrophysical radiation mechanisms Jupiter planetary atmospheres plasma instability plasma radiofrequency heating radioastronomy electron-cyclotron maser emission streaming distributions elliptically polarized emission Jupiter drifting electron distributions electrons stream nonzero mean velocity magnetic field lines analytical expression semirelativistic growth rate magneto-ionic modes geometric analysis }, mynotes={UNREAD}, } @ARTICLE{DemekhovApr94, author={Demekhov, A.G. and Trakhtengerts, V.Yu.}, title={ A mechanism of formation of pulsating aurorae }, journal={Journal of Geophysical Research}, volume={99}, number={A4}, year={1994}, month={Apr}, pages={5831-41}, abstract={ The authors consider a mechanism of pulsating aurora formation relevant for the substorm recovery phase. It is based on the spikelike regime of whistler cyclotron instability in auroral ducts with enhanced plasma density, elongated with geomagnetic field lines. The authors present the rigorously derived self-consistent quasi-linear theory of flow cyclotron maser operation, which describes spikelike regimes of whistler wave generation and energetic particle precipitation in a duct. They show that pulsations are formed due to broadening of the resonance region in velocity space in the course of instability development. They have obtained theoretical estimations for temporal characteristics of pulsating auoral patches. The pulsating regime is realized when the energetic electron number density is below some critical value depending on background plasma density and particle source parameters. Pulsation "on" time is determined by the nonlinear instability dynamics whereas "off" time is nearly equal to the time of reaching the wave excitation threshold. The authors compare their analytical and numerical results with known experimental data and show that the model explains reasonably most observations concerning pulsation time pattern, electron precipitation fluxes, VLF wave spectrum dynamics, latitudinal and longitudinal dependencies of pulsation characteristics, etc. Preliminary estimates are also made of nonlinear particle trapping effects during the maximum of the on phase that can give rise to a fine temporal structure of pulsations }, keywords={ atmospheric electron precipitation aurora ionosphere magnetosphere upper atmosphere mechanism formation pulsating aurora substorm recovery phase spikelike regime spike whistler cyclotron instability auroral duct plasma instability ionosphere magnetosphere selfconsistent quasilinear theory flow cyclotron maser whistler wave generation energetic particle precipitation resonance region broadening of t velocity space pulsating auoral patch nonlinear instability electron precipitation }, mynotes={UNREAD}, } @ARTICLE{PakterNov93, author={Pakter, R. and Rizzato, F.B.}, title={ Numerical analysis of mismatch and dispersive effects on an arbitrary amplitude cyclotron resonance maser accelerator }, journal={Physica Scripta}, volume={48}, number={5}, year={1993}, month={Nov}, pages={598-602}, abstract={ The authors perform a self-consistent numerical analysis of a cyclotron resonance maser accelerator operating with arbitrary amplitudes of the maser beam. They investigate the interplay involving wave dispersion, a possible mismatch between cyclotron and wave frequencies, and the initial gyrophase spread of the distribution function for the accelerating particles. For small enough initial values of particle energies, rapid phase bunching takes place. In this case, they show how a convenient choice of the mismatch parameter can greatly reduce the limiting influence of wave dispersion on particle bulk acceleration. On the other hand, when initial energies are larger, it is shown that phase bunching does not occur and that a considerable energy spread may set in. Even in this case, however, a convenient choice of the mismatch parameter can still cause energization for a fraction of the injected particles, although beam quality is reduced. A comparison between numerical simulation and the self-consistent macroparticle analysis is also carried out }, keywords={ collective accelerators cyclotron masers electron beam accelerator gyration guide magnetic field mismatch dispersive effects arbitrary amplitude cyclotron resonance maser accelerator self-consistent numerical analysis maser beam wave dispersion initial gyrophase spread rapid phase bunching energization }, mynotes={UNREAD}, } @ARTICLE{MelroseMay93, author={Melrose, D.B. and Dulk, G.A.}, title={ Electron cyclotron maser emission at oblique angles }, journal={Planetary and Space Science}, volume={41}, number={5}, year={1993}, month={May}, pages={333-9}, abstract={ Observations of elliptically polarized bursts of decametric radio emission from Jupiter with axial ratios of the polarization ellipse 0.2f/sub ce/), nd that it generally retains the highest extraordinary mode growth rate, dominating over the O mode for very small (<0.15) or high (>1) values of f/sub pe//f/sub ce/. This mode is therefore expected to prevail, at least locally, in the source region. The width of the instability range is found to be mostly determined by the ratio n/sub hot//n/sub cold/, which must typically lie between 1 and 100. When n/sub hot//n/sub cold/<10, T/sub cold/ needs in addition to be smaller than 0.2 T/sub hot/. Specific signatures of modes and implications for auroral kilometric radiation are derived }, keywords={ astronomical masers astrophysical radiation mechanisms atmospheric radiation cyclotron masers dispersion relations plasma instability plasma-beam interactions relativistic plasmas AKR magnetosphere maser cyclotron instabilities multicomponent plasmas cold-cool plasma artificial beam-plasma phenomena relativistic mode electron gyrofrequency semirelativistic dispersion relation extraordinary mode growth rate source region auroral kilometric radiation }, mynotes={UNREAD}, } @ARTICLE{VlasovJun92, title={ Excitation of auroral hectometric radioemission at the cyclotron maser resonance ( omega /sub p/>or approximately= omega /sub H/) }, journal={Fizika Plazmy}, volume={18}, number={6}, year={1992}, month={Jun}, pages={757-67}, abstract={ The excitation of auroral hectometric and kilometric radio-emission (AHR and AKR) and the cyclotron maser resonance (CMR) is studied in a relatively dense plasma ( omega /sub p/>or approximately= omega /sub H/). It is shown that among all the cyclotron waves only the second harmonic of the fast extraordinary mode and the first harmonic of the ordinary mode can have large amplification coefficients. It is concluded that the principal condition for excitation of AHR at the CMR by auroral electron beams is the presence of a two-dimensional small-scale variation in the plasma density. If the transverse density variation prevents waves from leaving the spatial excitation region, then the longitudinal density variation, which tends to cancel out the monotonic variation of the geomagnetic field, inhibits the escape of waves from the phase excitation region, i.e. from the CMR. The small-scale nonuniformity of the auroral plasma measured from spacecraft has parameters which satisfy the conditions derived in the work for the excitation of auroral radioemission. It is concluded that the complicated dynamic structure of the AHR and AKR spectra that are measured reflects the dynamics of the small-scale plasma density variation in the region where the emission is generated }, keywords={ atmospheric radiation ionosphere magnetosphere plasma radioemission excitation auroral kilometric radioemission ionosphere auroral hectometric radioemission cyclotron maser resonance radio-emission dense plasma cyclotron waves second harmonic fast extraordinary mode first harmonic ordinary mode amplification coefficients auroral electron beams transverse density variation longitudinal density variation geomagnetic field spacecraft dynamic structure spectra }, mynotes={UNREAD}, } @ARTICLE{WingleeNov92, author={Winglee, R.M. and Menietti, J.D. and Wong, H.K.}, title={ Numerical simulations of bursty radio emissions from planetary magnetospheres }, journal={Journal of Geophysical Research}, volume={97}, number={A11}, year={1992}, month={Nov}, pages={1713-19}, abstract={ The Voyager spacecraft observed both smooth and bursty radio emissions from Uranus and Neptune. These emissions are known to be freely propagating primarily in the right-hand circularly polarised (RCP) mode with the bursty emissions having burst periods as short as a few tenths of a second and the smooth emissions being observed over periods of a few hours. While the smooth emission is probably due to the electron cyclotron maser instability some other processes must be at work to produce the bursty emissions. It is proposed that one important difference in mechanisms is that the smooth emissions are associated with continuous injection of electrons while the bursty emissions are associated with impulsive injection. In the latter case, the electron distribution can develop a beam feature with a temperature anisotropy }, keywords={ Neptune planetary atmospheres radioastronomy Uranus radio emission burst planet magnetosphere numerical model radioastronomy mechanism bursty radio emissions Uranus Neptune right-hand circularly polarised electrons impulsive injection }, mynotes={UNREAD}, } @ARTICLE{Shi-Chang-ZhangOct92, title={ Unified single-particle theory of free-electron-maser amplifiers }, journal={Physical Review A (Statistical Physics, Plasmas, Fluids, and RelatedInterdisciplinary Topics)}, volume={46}, number={8}, year={1992}, month={Oct}, pages={5154-60}, abstract={ Based on the model of the equilibrium electron beam, the electron cyclotron system (ECS), a unified single-particle approach is developed for the free-electron-maser (gyrotron, cyclotron autoresonance maser, and gyropeniotron) amplifiers. The dispersion equation is derived in detail in terms of the coupling of the ECS with the waveguide field. Unlike the previous model of the beamlet and its treatment, here the variation rate of the perturbed current to the gyroradius is considered. This approach can be used to analyze the gyroradius spread. Results show the existence of the gyropeniotron interaction, even when the gyrotron interaction extinguishes. The gyropeniotron instability is demonstrated to be based on the radial resonance of the electrons with the perturbation fields. The special case of a thin axis-encircling electron beam is discussed, and it is found that the gyrotron instability and the gyropeniotron instability cannot simultaneously appear for the given initial parameters and the azimuthal mode index }, keywords={ dispersion relations free electron lasers masers unified single-particle theory gyrotron amplifier coaxial hollow electron beam cylindrical waveguide free-electron-maser amplifiers equilibrium electron beam electron cyclotron system cyclotron autoresonance maser gyropeniotron dispersion equation coupling waveguide field variation rate perturbed current gyroradius instability radial resonance azimuthal mode index }, mynotes={UNREAD}, } @ARTICLE{Jeong-Sik-ChoiApr92, author={Jeong-Sik Choi, Sun-Kook Kim and Duk-In Choi}, title={ Generalized distribution function for the electron cyclotron resonance maser interaction including the effect of AC space charge waves }, journal={Journal of the Korean Physical Society}, volume={25}, number={2}, year={1992}, month={Apr}, pages={166-9}, abstract={ The general perturbed distribution function for the cyclotron resonance maser (CRM) interaction that takes into account self-consistent couplings between the TE, TM, and AC space charge modes in a circular waveguide is derived within the frame of the linearized Vlasov-Maxwell equations. The authors expect this distribution function to be a useful form for analyzing the various types of CRM devices, especially for using high-density, high-current electron beams. It is predicted that the growth rate due to AC space charge effects may be enhanced }, keywords={ gyrotrons masers space charge Vlasov equation high density high current electron beams electron cyclotron resonance maser AC space charge waves general perturbed distribution function self-consistent couplings circular waveguide linearized Vlasov-Maxwell equations }, mynotes={UNREAD}, } @ARTICLE{DanlyJul92, author={Danly, B.G. and Hartemann, F.V. and Chu, T.S. and Legorburu, P. and Menninger, W.L. and Temkin, R.J. and Faillon, G. and Mourier, G.}, title={ Long-pulse millimeter-wave free-electron laser and cyclotron autoresonance maser experiments }, journal={Phys. Fluids B, Plasma Phys. (USA), Physics of Fluids B (Plasma Physics)}, volume={4}, number={7}, year={1992}, month={Jul}, pages={2307-14}, abstract={ Experimental results on high-power long-pulse free-electron laser (FEL) and cyclotron autoresonance maser (CARM) experiments are summarized. Single-mode operation of a free-electron laser oscillator at 27.4 GHz with a Bragg resonator has been obtained, with an output power of 990 kW for a beam energy of 320 keV and transmitted current of 30 A, corresponding to an efficiency of 10.3%. Free-electron maser (FEM) amplifier operation at 35 GHz has yielded a gain of 26 dB with an output power of 800 kW, corresponding to an efficiency of 8.6%. CARM oscillator experiments at 32 GHz with a different electron gun have yielded lower powers because of poor beam quality; planned CARM experiments are discussed }, keywords={ free electron lasers masers optical resonators oscillators single-mode operation free electron maser amplifier operation high-power long-pulse millimetre-wave free-electron laser cyclotron autoresonance maser experiments Bragg resonator electron gun 27.4 GHz 30 A 26 dB 990 kW 35 GHz 320 keV 800 kW 32 GHz }, mynotes={UNREAD}, } @ARTICLE{FreundMay92, author={Freund, H.P. and Chen, C.}, title={ Comparison of gyro-averaged and non-gyro-averaged nonlinear analyses of cyclotron autoresonance masers }, journal={International Journal of Electronics}, volume={72}, number={5-6}, year={1992}, month={May}, pages={1005-31}, abstract={ The nonlinear evolution of the cyclotron autoresonance maser (CARM) is investigated numerically using two distinct three-dimensional formulations of the interaction. These formulations differ primarily in that one (CSPOT) relies upon a gyro-averaged orbit treatment, while the other (CHARM) imposes no gyro-average. The authors' purpose is to compare and contrast the results of these different formulations for CARMs with a range of physically interesting parameters. Both formulations employ a representation of the electromagnetic field based upon a superposition of the TE and TM modes of a loss-free cylindrical waveguide, and they are fully multi-mode. Waveguide losses are included by means of a constant loss rate. The distinction between these formulations is in the electron dynamics. The CSPOT formulation imposes a gyro-average on the electron orbit equations in which the guiding-centre motion is neglected. Thus, the electron motion is reduced to a set of three equations per particle. In contrast, the CHARM formulation makes no distinction between the Larmor and guiding-centre motion, and integrates the complete Lorentz force equations (six) per electron }, keywords={ masers gyro-averaged analysis nongyro-averaged analysis nonlinear evolution EM field representation nonlinear analyses cyclotron autoresonance masers three-dimensional formulations gyro-averaged orbit treatment CARMs loss-free cylindrical waveguide electron dynamics CSPOT formulation electron orbit equations guiding-centre motion CHARM formulation Lorentz force equations }, mynotes={UNREAD}, } @ARTICLE{LinMay92, author={Lin, A.T. and Kaw, P.K.}, title={ Absolute instability in finite length electron cyclotron maser systems }, journal={International Journal of Electronics}, volume={72}, number={5-6}, year={1992}, month={May}, pages={887-94}, abstract={ The temporal growth rate of the absolute instability in finite length electron cyclotron maser systems has been theoretically calculated and confirmed by particle simulations. The nonlinear saturation mechanism is due to that in the unstable system, the nonlinear electron phase shift induced by the wave field gives rise to a virtual end plane which tends to shorten the effective interaction length and brings the system into the marginal stable state. In the system far above threshold, the virtual plane first oscillates and eventually approaches a steady state location. This early oscillating behaviour strongly correlates to the initial pronounced spiky temporal structure in the output power }, keywords={ gyrotrons masers simulation stability finite length electron cyclotron maser systems temporal growth rate absolute instability particle simulations nonlinear saturation mechanism nonlinear electron phase shift wave field virtual end plane effective interaction length marginal stable state oscillating behaviour }, mynotes={UNREAD}, } @ARTICLE{McCurdyMay92, title={ Self-consistency in the quasi-linear theory of electron cyclotron masers }, journal={International Journal of Electronics}, volume={72}, number={5-6}, year={1992}, month={May}, pages={861-72}, abstract={ The rate equation coefficients in the quasi-linear theory of the electron cyclotron maser are calculated self-consistently by using the true oscillator frequency. Theoretical corrections to the growth rate, oscillation frequency and saturation are calculated and compared with experiment. It is found that the self-consistency requirement can be met in a simple way which substantially improves the theory }, keywords={ masers quasilinear theory quasi-linear theory electron cyclotron masers rate equation coefficients true oscillator frequency growth rate oscillation frequency saturation self-consistency requirement }, mynotes={UNREAD}, } @ARTICLE{Huang-GuangliOct91, author={Huang Guangli and Wang Deyu}, title={ The effects of plasma ambient parameters on spike emissions }, journal={Acta Astrophysica Sinica}, volume={11}, number={4}, year={1991}, month={Oct}, pages={352-61}, abstract={ On the basis of the theory of electron-cyclotron maser instabilities, the effects of the plasma ambient parameter omega /sub pe// Omega /sub e/ on the properties of the spike emissions are discussed, including the physical meaning of this parameter, its magnitude, and the polarization and harmonic structure of the radio spikes, which are sensitive to this parameter }, keywords={ astronomical masers astrophysical plasma astrophysical radiation mechanisms electromagnetic wave polarisation solar corona solar flares solar radiofrequency radiation solar flares ambient plasma solar coronal plasma solar radio spike emission Sun radio spikes polarisation ordinary mode growth rate fast extraordinary mode growth rate plasma instability growth rate plasma ambient parameters electron-cyclotron maser instabilities omega /sub pe// Omega /sub e/ harmonic structure }, mynotes={UNREAD}, } @ARTICLE{McKeanDec91, author={McKean, M.E. and Winglee, R.M.}, title={ A model for the frequency fine structure of auroral kilometric radiation }, journal={Journal of Geophysical Research}, volume={96}, number={A12}, year={1991}, month={Dec}, pages={21055-70}, abstract={ One of the more interesting and as yet unexplained features of auroral kilometric radiation (AKR) is the frequency fine structure observed in wideband spectrograms. This fine structure consists of emission features that drift in frequency with time, and of banded emission structure. Both positive and negative drifts are observed. While the electron cyclotron maser instability is widely believed to be the source of AKR, no proposed explanation for the frequency fine structure seen in AKR has been confirmed. The authors propose a model for AKR frequency fine structure in which the fine structure is a natural consequence of the emission of electron cyclotron maser radiation in a nonuniform magnetic field. This model is examined by using one-dimensional, electromagnetic, particle-in-cell simulations. Maser radiation is emitted as individual wave packets that combine to form the drifting emission features that make up the fine structure }, keywords={ atmospheric radiation magnetosphere LF AKR radiowave emission frequency drift magnetosphere model frequency fine structure auroral kilometric radiation banded emission structure electron cyclotron maser radiation nonuniform magnetic field one-dimensional particle-in-cell simulations 30 to 300 kHz }, mynotes={UNREAD}, } @ARTICLE{VlasovSep91, title={ X-mode generation mechanism of the auroral kilometric radiation in the inhomogeneous plasma }, journal={Planetary and Space Science}, volume={39}, number={9}, year={1991}, month={Sep}, pages={1223-32}, abstract={ A study is made of the influence of plasma and geomagnetic field inhomogeneities (longitudinal and transverse) upon the X-mode generation process of auroral kilometric radiation (AKR) due to cyclotron maser resonance. It is shown that the generation of AKR by auroral electron beams of typical energies 1-10 keV takes effect only in those local regions of a discrete arc where the regular longitudinal inhomogeneity of the geomagnetic field is compensated by the longitudinal inhomogeneity of magnetospheric plasma. Outside of such regions, waves recover too rapidly from cyclotron maser resonance as a consequence of a decrease of the longitudinal component of the wave vector. A critical study is made of an earlier solution to this problem through wave generation, with the transverse component of the refractive index being close to unity }, keywords={ magnetosphere AKR radiowave emission magnetosphere X-mode generation mechanism auroral kilometric radiation inhomogeneous plasma cyclotron maser resonance auroral electron beams discrete arc regular longitudinal inhomogeneity 30 to 300 kHz 1 to 10 keV }, mynotes={UNREAD}, } @ARTICLE{VlasovFeb91, title={ Generation of auroral kilometric radio emission at the cyclotron maser resonance }, journal={Fizika Plazmy}, volume={17}, number={2}, year={1991}, month={Feb}, pages={165-76}, abstract={ A linear mechanism of auroral kilometric radiation (AKR) generation at the maser cyclotron resonance (MCR) in an inhomogeneous multidimensional plasma is developed. The model distribution functions introduced by the author for longitudinal and transverse electron beams allow one to obtain X- and O-mode growth rates in the form of elemental functions. The key idea of the study is the MCR time taking into account all processes leading to the emission of waves from the MCR. It is shown that the MCR time can be sufficient for AKR generation in isolated regions of the auroral plasma. For the X-mode these are the parts of the plasma where the longitudinal gradient of the geomagnetic field is compensated by the plasma density gradient. The O-mode is generated only in those local regions where there is an extremely small longitudinal plasma density gradient. The theoretical minimum width of the AKR spectral line obtained coincides with the minimal measured line width of 5 Hz. It is concluded that the discrete AKR spectrum is related to the inhomogeneous structure of the auroral plasma }, keywords={ atmospheric radiation magnetosphere plasma longitudinal growth rates X-mode growth rates magnetosphere auroral kilometric radio emission cyclotron maser resonance AKR inhomogeneous multidimensional plasma distribution functions transverse electron beams O-mode growth rates elemental functions auroral plasma geomagnetic field plasma density gradient inhomogeneous structure }, mynotes={UNREAD}, } @ARTICLE{RobinsonAug91, title={ Electron-cyclotron maser emission in solar microwave spike bursts }, journal={Solar Physics}, volume={134}, number={2}, year={1991}, month={Aug}, pages={299-314}, abstract={ A new model is developed for electron-cyclotron maser emission from flaring loops, which incorporates competition between driving of the instability and maser-induced relaxation, together with interactions between small neighboring regions of unstable plasma. This results in a picture in which radiation is emitted in bursts from regions whose length scale is determined self-consistently by previous bursts, while the unstable plasma fluctuates about the point, close to marginal stability, at which driving of the instability is balanced by relaxation due to maser-induced electron diffusion. Under the conditions applicable to flaring loops, time scales of fundamental x-mode (x1) driving and saturation are approximately equal at approximately 1 ms, resolving a (10/sup 4/-10/sup 6/)-fold discrepancy in previous models and agreeing with the observed time scales of microwave spike bursts }, keywords={ astronomical masers plasma instability solar radiofrequency radiation solar microwave spike bursts model electron-cyclotron maser emission flaring loops instability maser-induced relaxation unstable plasma electron diffusion }, mynotes={UNREAD}, } @ARTICLE{BratmanAug90, author={Bratman, V.L. and Denisov, G.G. and Lukovnikov, D.A.}, title={ Theory of cyclotron autoresonance masers with open electrodynamic system }, journal={Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika}, volume={33}, number={8}, year={1990}, month={Aug}, pages={976-86}, abstract={ A study is made in the dipole approximation of the resonance interaction of a helical electron beam with the field of a quasioptical wave beam with allowance for the variability of the amplitude and phase velocity of the synchronous wave on the particle trajectories. A detailed study is made of the example of a cyclotron autoresonance maser with resonator formed by two annular spheroidal mirrors, for which the modes with the smallest start currents are found and the nonlinear masing regime is investigated }, keywords={ electrodynamics gyrotrons masers theory cyclotron autoresonance masers open electrodynamic system dipole approximation resonance interaction helical electron beam quasioptical wave beam amplitude phase velocity synchronous wave particle trajectories annular spheroidal mirrors start currents nonlinear masing regime }, mynotes={UNREAD}, } @ARTICLE{Wang91, author={Wang, Q.S. and McDermott, D.B. and Luhmann, N.C., Jr.}, title={ Magnetically tapered CARM for high power }, journal={Proc. SPIE - Int. Soc. Opt. Eng. (USA), Proceedings of the SPIE - TheInternational Society for Optical Engineering}, volume={1407}, number={}, year={1991}, month={}, pages={209-16}, abstract={ A cyclotron autoresonance maser (CARM) inherently demonstrates high efficiency due to its autoresonant feature. Tapering the axial magnetic field can further enhance the CARM's already attractive efficiency. A self-consistent, three-dimensional, nonlinear numerical simulation code has been developed and used to optimize the design of CARM amplifiers, including an axial magnetic field taper. There are usually two free parameters involved in tapering the magnetic field linearly, namely, the tapering rate and taper-starting position. It will be shown in the simulation results that these parameters can be reduced to only one, that is, the tapering rate. By starting the magnetic field taper directly before the first electron crossover occurs, both optimum efficiency and growth rate can be obtained }, keywords={ digital simulation masers optimum growth rate magnetically tapered CARM 3D simulation code design optimisation high power cyclotron autoresonance maser high efficiency autoresonant feature nonlinear numerical simulation code CARM amplifiers axial magnetic field taper tapering rate taper-starting position simulation results optimum efficiency }, mynotes={UNREAD}, } @ARTICLE{LadreiterMar91, title={ The cyclotron maser instability: application to low-density magnetoplasmas }, journal={Astrophysical Journal}, volume={370}, number={1}, year={1991}, month={Mar}, pages={419-26}, abstract={ The cyclotron maser instability is applied to low-density magnetoplasmas (f/sub p//f/sub c/<0.01) to derive simple expressions relating the wave-emergent angle theta of the amplified wave and the ratio f/f/sub c/ at the source to the normalized parallel bulk velocity beta /sub //0/ of the instability (characteristic for an auroral electron distribution function) via the equations cos theta = beta /sub //0/ and f/f/sub c/=(1- beta /sub //0//sup 2/)/sup -1/2/. Loss cone and holelike instabilities are assumed to be responsible for amplification of the electromagnetic wave. For beta /sub //0/, corresponding to 1-10 keV, the cone half angle theta of the amplified wave is nearly perpendicular with respect to the magnetic field and is decreasing as beta /sub //0/ increases. The wave frequency at the source is slightly above the gyrofrequency but also considerably different to the R-X cutoff; thus, the refractive index is close to unity at the radio source. No strong refraction along the ray path is therefore expected for f/sub p//f/sub c/<<1. The results are highly relevant to the lower frequency auroral emission of Jupiter and of Saturn }, keywords={ Jupiter planetary atmospheres plasma instability Saturn loss cone instability magnetized plasma magnetoplasma planetary atmosphere magnetosphere cyclotron maser instability low-density wave-emergent angle amplified wave parallel bulk velocity holelike instabilities }, mynotes={UNREAD}, } @ARTICLE{ChenJul91, author={Chen, C. and Danly, B.G. and Davies, J.A. and Menninger, W.L. and Wurtele, J.S. and Zhang, G.}, title={ CARM amplifier theory and simulation }, journal={Nucl. Instrum. Methods Phys. Res. A, Accel. Spectrom. Detect. Assoc. Equip.(Netherlands), Nuclear Instruments & Methods in Physics Research, Section A(Accelerators, Spectrometers, Detectors and Associated Equipment)}, volume={A304}, number={1-3}, year={1991}, month={Jul}, pages={593-600}, abstract={ The theory and simulation of cyclotron autoresonance maser (CARM) amplifiers are presented, including studies of amplifier phase stability, multimode phenomena, and susceptibility to absolute instabilities. Recent results include particle-in-cell simulations of the onset of absolute instabilities and numerical modeling of multimode effects. Phase stability studies indicate that the output phase of CARM amplifiers is relatively insensitive to fluctuations in beam energy, pitch, and current, for optimized designs; simulations show a phase sensitivity of approximately 2 degrees per percent beam energy variation. An experimental design for a long-pulse 17 GHz CARM amplifier is presented }, keywords={ gyrotrons laser modes laser theory masers physics computing amplifier instability susceptibility current fluctuations beam energy fluctuations pitch fluctuations K-band SHF CARM amplifier theory cyclotron autoresonance maser amplifier phase stability multimode phenomena absolute instabilities particle-in-cell simulations numerical modeling output phase CARM amplifiers phase sensitivity beam energy variation 17 GHz }, mynotes={UNREAD}, } @ARTICLE{BezchastnovApr91, author={Bezchastnov, V.G. and Pavlov, G.G.}, title={ Quantum relativistic theory of the cyclotron radiation in strongly-magnetized plasmas: fine structure of the spectra and maser effect }, journal={Astrophysics and Space Science}, volume={178}, number={1}, year={1991}, month={Apr}, pages={1-39}, abstract={ The full quantum relativistic treatment of cyclotron/synchrotron emission and absorption in a tenuous plasma with superstrong magnetic fields is developed for the case when the radiation modes are linearly polarized. Spectra of emission, absorption and polarization are investigated both for a thermal distribution of the radiating particles and for a distribution with anisotropic temperature. Quantum relativistic effects lead to a fine structure of the cyclotron harmonics with typical spacing approximately nu Omega /sub B/(B/B/sub c/), where nu =1, 2,. . .is the harmonic number, and Omega /sub B/ is the cyclotron frequency. For essentially nonrelativistic temperatures the fine structure can be observed in a wide angle range, cos/sup 2/ theta >>T/sub ////mc/sup 2/, for distributions with strong transverse anisotropy T/sub perpendicular to />>T/sub ///. The transverse anisotropy may also lead to maser amplification of the cyclotron radiation in the narrow frequency ranges corresponding to the fine structure peaks in the emissivity spectra. These effects can be observed in the X-ray and gamma-ray radiation from strongly magnetized neutron stars }, keywords={ astronomical masers astronomical spectra astrophysical plasma astrophysical radiation mechanisms electromagnetic wave polarisation gamma-ray sources (astronomical) neutron stars relativistic plasmas stellar radiation synchrotron radiation X-ray binary stars X-ray sources (astronomical) X-ray emission cyclotron maser emission spectra spectral fine structure absorption spectra polarisation spectra temperature anisotropy linearly polarised radiation modes fine structure spacing gamma-ray bursters cyclotron radiation strongly-magnetized plasmas maser effect quantum relativistic treatment cyclotron/synchrotron emission tenuous plasma superstrong magnetic fields thermal distribution radiating particles anisotropic temperature fine structure cyclotron harmonics harmonic number cyclotron frequency nonrelativistic temperatures transverse anisotropy maser amplification narrow frequency ranges fine structure peaks emissivity spectra gamma-ray radiation strongly magnetized neutron stars 4.41 GT }, mynotes={UNREAD}, } @ARTICLE{Shi-BingrenJan91, author={Shi Bingren and Wu, C.S.}, title={ Direct amplification of electromagnetic waves by a synchrotron maser instability }, journal={Chinese Physics}, volume={11}, number={1}, year={1991}, month={Jan}, pages={92-7}, abstract={ Direct amplification of electromagnetic waves by a synchrotron maser instability is discussed, which is based on the resonant interaction of dilute moderately relativistic electrons with a monoenergetic hollow-beam distribution and the electromagnetic eigenmode in the background plasma. The authors are mainly concerned about the parameter regime of mod omega /sub e// Omega /sub e/ mod 1, the dominant emissions below Omega /sub e/ are strong whistlers and lower hybrid waves while above Omega /sub e/ the dominant waves are electrostatic Berstein and upper hybrid waves }, keywords={ atmospherics electron beams F-region ionosphere plasma plasma waves plasma-beam interactions space research whistlers ionosphere active probing electron beam injections MF EM wave emissions plasma waves spectra HF whistlers cutoff frequency F-region EM fundamental Z-mode waves electrostatic Bernstein waves second harmonic x-mode waves harmonic frequencies half harmonic frequencies ELF VLF LF Echo 7 experiment altitude electron plasma frequency cyclotron frequency plasma waves parallel beam energy electrostatic upper hybrid waves perpendicular beam energy maser instability strong whistlers lower hybrid waves 200 to 300 km 0 to 8 MHz }, mynotes={UNREAD}, } @ARTICLE{UngstrupMay90, author={Ungstrup, E. and Bahnsen, A. and Wong, H.K. and Andre, M. and Matson, L.}, title={ Energy source and generation mechanism for auroral kilometric radiation }, journal={Journal of Geophysical Research}, volume={95}, number={A5}, year={1990}, month={May}, pages={5973-81, 6113-14}, abstract={ The orbit of the Swedish satellite Viking was optimized for observations of plasma phenomena in the auroral acceleration regions, including auroral kilometric radiation. The auroral kilometric radiation (AKR) is the strongest electromagnetic radiation produced on auroral field lines, and the Viking satellite passed through the source region of this radiation on many orbits, as evidenced by the very strong signals observed at the electron cyclotron frequency. For the first time, electron distribution functions were observed inside the AKR source region and immediately adjacent to the source region. The particle data show the presence of energetic electrons in and around the source region and also of upgoing ion beams of several keV energy in and only in the source region. Thus the particle data show clear signatures of parallel electric potentials both above and below the AKR source. The authors observations are in agreement with the cyclotron maser instability theory including the effect of a parallel electric field }, keywords={ atmospheric radiation magnetosphere radiowave emission AKR energy source AD 1986 LF magnetosphere plasma instability generation mechanism auroral kilometric radiation electromagnetic radiation source region electron distribution functions energetic electrons upgoing ion beams parallel electric potentials cyclotron maser instability theory }, mynotes={UNREAD}, } @ARTICLE{KhoApr90, author={Kho, T.H. and Lin, A.T.}, title={ Efficiency dependence on beam current and input power in a cyclotron autoresonance maser amplifier }, journal={Physics of Fluids B (Plasma Physics)}, volume={2}, number={4}, year={1990}, month={Apr}, pages={822-7}, abstract={ The efficiency dependence of a cyclotron autoresonance maser (CARM) amplifier on electron beam current and input power is investigated using computer simulations and a theoretical model is presented to explain the findings. For a resonantly tuned CARM, the efficiency is found to initially increase and then decrease with beam current, while for an optimally detuned CARM, the efficiency drops with any increase in beam current. If the current is kept constant, the efficiency is also found to drop as the input wave power is increased. Force bunching is found to play an important role in reducing the efficiency at high-beam current, which may make extension to high power through increasing beam current more difficult to achieve }, keywords={ electron beams masers force bunching beam current input power cyclotron autoresonance maser amplifier efficiency dependence CARM electron beam current computer simulations high-beam current }, mynotes={UNREAD}, } @ARTICLE{MeniettiJan90, author={Menietti, J.D. and Wong, H.K. and Wah, D.A. and Lin, C.S.}, title={ Source region of the smooth high-frequency nightside Uranus kilometric radiation: a ray-tracing study }, journal={Journal of Geophysical Research}, volume={95}, number={A1}, year={1990}, month={Jan}, pages={51-60}, abstract={ Assuming the cyclotron maser instability is the source mechanism of the smooth high-frequency, nightside component of Uranian kilometric radiation, a plasma density model is developed for the nightside at r<4.2 r/sub u/ based on radio wave observations of the Planetary Radio Astronomy instrument on board the Voyager 2 spacecraft. Using this plasma model and the Q3 magnetic field model (Connerney et al., 1987), a systematic ray tracing of right-hand extraordinary (RX) emission is performed from a grid of nightside sources along magnetic field lines at frequencies just above the RX cutoff. By requiring that the rays satisfy several observational constraints, the authors specify the source region with more accuracy than previously prescribed }, keywords={ astrophysical plasma planetary atmospheres planetary magnetism Uranus right hand extraordinary emission magnetosphere atmosphere smooth high-frequency nightside Uranus kilometric radiation ray-tracing study cyclotron maser instability source mechanism plasma density model Voyager 2 magnetic field cutoff }, mynotes={UNREAD}, } @ARTICLE{BeschastnovMar89, author={Beschastnov, V.G. and Pavlov, G.G.}, title={ Cyclotron absorption and emission in a strongly magnetized plasma }, journal={Zhurnal Eksperimental'noi i Teoreticheskoi Fiziki}, volume={95}, number={3}, year={1989}, month={Mar}, pages={832-7}, abstract={ Cyclotron absorption and emission along an arbitrarily strong magnetic field in a tenuous electron-positron plasma is considered on the basis of an exact quantum-relativistic treatment. The maser effect is rigorously proved to be impossible in this case. Simple expressions are obtained for the absorption coefficient and emissivity of a thermal plasma. It is shown that the nonequidistance of the Landau levels for an anisotropic plasma-particle distribution function may lead to a new type of oscillations in the cyclotron absorption and emission spectra }, keywords={ electromagnetic wave absorption electromagnetic wave propagation in plasma emissivity relativistic plasmas cyclotron emission spectra cyclotron absorption spectra strongly magnetized plasma arbitrarily strong magnetic field tenuous electron-positron plasma exact quantum-relativistic treatment maser effect absorption coefficient emissivity thermal plasma nonequidistance Landau levels anisotropic plasma-particle distribution function }, mynotes={UNREAD}, } @ARTICLE{Kleva88, author={Kleva, R.G. and Baruch Levush and Sprangle, P.}, title={ Optical guiding in the cyclotron autoresonance maser }, journal={Proc. SPIE - Int. Soc. Opt. Eng. (USA), Proceedings of the SPIE - TheInternational Society for Optical Engineering}, volume={1039}, number={}, year={1988}, month={}, pages={322-3}, abstract={ The effect of the electron beam on the propagation of a three-dimensional radiation beam in a cyclotron autoresonance maser amplifier is investigated numerically. In the exponential gain regime, it is shown that the natural tendency of the radiation beam to spread diffractively is overcome and the radiation beam is focused due to interaction with the electron beam. The nature of the focusing is found to depend on the relative magnitude of the Doppler-shifted wave frequency, omega /sub D/, and the relativistic gyrofrequency, Omega . The radiation beam can be transported without defocusing following saturation only if omega /sub D/ is slightly larger than Omega . Efficiencies in excess of 50% can be attained through the use of a tapered magnetic field }, keywords={ electron beam effects focusing masers optical guiding CARM electron beam three-dimensional radiation beam cyclotron autoresonance maser exponential gain regime focusing Doppler-shifted wave frequency relativistic gyrofrequency saturation tapered magnetic field }, mynotes={UNREAD}, } @CONFERENCE{Bezchastnov89, author={Bezchastnov, V.G. and Pavlov, G.G.}, title={ Quantum relativistic theory of cyclotron radiation in a strongly magnetised plasma with anisotropic temperature }, booktitle={Proceedings of an International School and Workshop on Plasma Astrophysics(ESA SP-285, vol.I)}, volume={}, number={}, year={1989}, month={}, pages={321-6}, abstract={ Cyclotron radiation in a tenuous, strongly magnetized plasma with anisotropic temperature is considered on the basis of quantum relativistic theory. It is shown that the quantum effects lead to oscillations in the spectra of the absorption coefficients and emissivity if the transverse temperature exceeds sufficiently the longitudinal one. Negative absorption (maser amplification) is also possible due to quantum effects in such a plasma if the angle between the magnetic field and the wave-vector is not too close to 0 or 90 degrees }, keywords={ astronomical spectra astrophysical plasma plasma magnetohydrodynamics plasma temperature plasma theory relativistic plasmas longitudinal plasma astrophysical plasma MHD cyclotron radiation strongly magnetised plasma anisotropic temperature quantum relativistic theory oscillations spectra absorption coefficients emissivity transverse temperature maser amplification magnetic field wave-vector }, mynotes={UNREAD}, } @ARTICLE{WongMay89, author={Wong, H.K. and Krauss-Varban, D. and Wu, C.S.}, title={ On the role of the energy of suprathermal electrons in the generation of auroral kilometric radiation }, journal={Journal of Geophysical Research}, volume={94}, number={A5}, year={1989}, month={May}, pages={5327-36}, abstract={ Satellite observations have identified second harmonic auroral kilometric radiation in part in source regions where the electron plasma frequency is known to be much smaller than the electron cyclotron frequency. These observations as well as certain observations of the O mode fundamental radiation have raised some controversy because conventional discussions predict their generation to be more favorable in a high-density plasma; the fundamental X mode dominating otherwise. The author reexamines the relativistic dispersion equation based on the cyclotron maser theory for a DGH distribution of energetic electrons. The purpose is to identify and understand the physical conditions under which fundamental O mode and second harmonic X mode radiations can dominate over fundamental X mode emission in low-density source regions }, keywords={ atmospheric radiation magnetosphere plasma magnetosphere atmosphere radiation energy suprathermal electrons auroral kilometric radiation second harmonic source regions electron plasma frequency electron cyclotron frequency fundamental radiation high-density plasma X mode relativistic dispersion equation maser DGH distribution }, mynotes={UNREAD}, } @ARTICLE{Le-QueauMar89, author={Le Queau, D. and Louarn, P.}, title={ Analytical study of the relativistic dispersion: application to the generation of the auroral kilometric radiation }, journal={Journal of Geophysical Research}, volume={94}, number={A3}, year={1989}, month={Mar}, pages={2605-16}, abstract={ The measurements recently performed by the Viking spacecraft have shown that, in addition to being cold plasma depleted, the source regions of the Auroral Kilometric Radiation (AKR) are characterized by a relatively denser, more energetic electron component (a few particles by cm/sup -3/, approximately=5 KeV). In order to properly study the Cyclotron Maser Instability (CMI) which is thought to be responsible for the AKR generation, it is thus necessary to include relativistic corrections in both the Hermitian and the antiHermitian parts of the dielectric tensor characterizing the linear properties of the plasma. Here one presents an analytical study of the corresponding dispersion equation which aims to describe stable and unstable waves having frequencies lying very close to the electronic gyrofrequency and propagating across the geomagnetic field with a perpendicular refractive index less than a few units }, keywords={ atmospheric radiation magnetosphere plasma plasma instability VLF AKR radiowave emission magnetosphere cyclotron maser instability plasma instability relativistic dispersion generation auroral kilometric radiation relativistic corrections unstable waves }, mynotes={UNREAD}, } @ARTICLE{PritchettJan89, author={Pritchett, P.L. and Winglee, R.M.}, title={ Generation and propagation of kilometric radiation in the auroral plasma cavity }, journal={J. Geophys. Res. (USA), Journal of Geophysical Research}, volume={94}, number={A1}, year={1989}, month={Jan}, pages={129-43}, abstract={ Two-dimensional particle simulations and three-dimensional ray-tracing calculations are used to investigate the generation and propagation of electromagnetic radiation produced by the electron cyclotron maser instability under conditions that prevail in the auroral plasma cavity. The simulations incorporate a continual flow of primary energetic electrons along the magnetic field. In such a driven system the maser instability leads to a quasi-steady state in which as much as 7% of the incident flux of electron energy is converted into radiation. The maximum radiation intensity occurs within 20-30 km from the injection point of the primary electrons, and the radiation consists of discrete wave packets with a spatial extent of 4-6 km parallel to the field. The magnetic field gradient is shown to be unimportant for these quasi-local properties of the maser instability. The ray path calculations are performed in a dipolar field geometry and retain the relativistic corrections to the wave dispersion }, keywords={ atmospheric radiation magnetosphere plasma instability magnetosphere radiowave emission AKR auroral kilometric radiation propagation kilometric radiation auroral plasma cavity particle simulations three-dimensional ray-tracing electromagnetic radiation electron cyclotron maser instability 30 to 300 kHz }, mynotes={UNREAD}, } @ARTICLE{KlevaNov88, author={Kleva, R.G. and Levush, B. and Sprangle, P.}, title={ Radiation focusing in the cyclotron autoresonance maser }, journal={Physics of Fluids}, volume={31}, number={11}, year={1988}, month={Nov}, pages={3171-3}, abstract={ In the cyclotron autoresonance maser, an electromagnetic wave is amplified by interaction with an electron beam. Because of the copropagating electron beam, the refractive index seen by the wave is modified from the vacuum index and the dielectric properties of the electron beam can alter the propagation of the radiation beam. This phenomenon is studied through the use of a source-dependent modal expansion of the fully three-dimensional radiation field. In the exponential gain regime, the natural tendency of the radiation beam to spread diffractively is overcome and the beam is focused. The nature of the focusing is found to depend on the relative magnitude of the Doppler-shifted wave frequency and the gyrofrequency }, keywords={ focusing masers radiation focusing cyclotron autoresonance maser electromagnetic wave amplified electron beam copropagating electron beam refractive index vacuum index dielectric properties source-dependent modal expansion three-dimensional radiation field exponential gain regime Doppler-shifted wave frequency gyrofrequency }, mynotes={UNREAD}, } @ARTICLE{KhoOct88, author={Kho, T.H. and Lin, A.T. and Liu Chen}, title={ Gyrophase-coherent electron cyclotron maser }, journal={Physics of Fluids}, volume={31}, number={10}, year={1988}, month={Oct}, pages={3120-6}, abstract={ The basic physics of an electron cyclotron maser driven by a coherently gyrophased, helical electron beam in a uniform magnetic field is analyzed. Theoretical predictions of gain enhancement and reduction in different regimes of the cyclotron instability, compared to a gyrotropic cyclotron maser, are verified with computer simulations. A physical explanation is presented for these findings. Beam-to-radiation energy conversion efficiency in the autoresonance regime is studied with computer simulations and compared with that for a gyrotropic beam }, keywords={ digital simulation masers gyrophase coherent electron cyclotron maser beam to radiation energy conversion efficiency helical electron beam uniform magnetic field gain enhancement reduction cyclotron instability computer simulations autoresonance regime computer simulations }, mynotes={UNREAD}, } @ARTICLE{DohlerOct88, author={Dohler, G. and Gallagher, D.}, title={ The small-signal theory of the cyclotron maser and other gyrotron-type devices }, journal={IEEE Transactions on Electron Devices}, volume={35}, number={10}, year={1988}, month={Oct}, pages={1730-45}, abstract={ The simplified cyclotron maser model presented by Lau (ibid., vol.ED-29, p.320-35, 1982) is analyzed under small-signal conditions with an exact analytical solution to the proper boundary condition taken across a thin, hollow rotating beam. Not only is the transverse electric field discontinuous but so are the axial and radial magnetic field components. The simultaneous presence of TE and TM modes are considered, leading to modifications in the dispersion relationships. The simultaneous inclusion of both modes and space charge leads to the main contribution to the theory: TE-TM coupling, off-resonance behavior, and subcutoff operation in the drift spaces of klystron-type devices. Also, since radial displacement of the beam is taken into account, the theory predicts a peniotron interaction in the cyclotron maser. Examples are presented of gyrotron or peniotron interactions in either the TE and TM modes as well as off-resonance and subcutoff }, keywords={ masers microwave tubes TE mode microwave tubes discontinuous transverse electric field small-signal theory cyclotron maser gyrotron-type devices boundary condition hollow rotating beam radial magnetic field components TM modes dispersion relationships space charge TE-TM coupling off-resonance behavior subcutoff operation drift spaces klystron-type devices radial displacement peniotron interaction }, mynotes={UNREAD}, } @ARTICLE{YoonMar87, author={Yoon, P.H. and Davidson, R.C.}, title={ Closed-form analytical model of the electron whistler and cyclotron maser instabilities in relativistic plasma with arbitrary energy anisotropy }, journal={Physical Review A (General Physics)}, volume={35}, number={6}, year={1987}, month={Mar}, pages={2619-30}, abstract={ Detailed properties of the cyclotron maser and whistler instabilities in a relativistic magnetized plasma are investigated for a particular choice of anisotropic distribution function F(p/sub perpendicular to //sup 2/, p/sub z/) that permits an exact analytical reduction of the dispersion relation for arbitrary energy anisotropy. The analysis assumes electromagnetic wave propagation parallel to a uniform applied magnetic field B/sub 0/e/sub z/. Moreover, the particular equilibrium distribution function considered in the present analysis assumes that all electrons move on a surface with perpendicular momentum p/sub perpendicular to /=const and are uniformly distributed in axial momentum from p/sub z/=-p/sub z/=const to p/sub z/=+p/sub z/=const (so-called 'waterbag' distribution in p/sub z/). This distribution function incorporates the effects of a finite momentum spread in the parallel direction. The resulting dispersion relation is solved numerically, and detailed properties of the cyclotron maser and whistler instabilities are determined over a wide range of energy anisotropy, normalized density omega /sub p//sup 2// omega /sub c//sup 2/, and electron energy }, keywords={ electromagnetic wave propagation in plasma plasma instability plasma waves relativistic plasmas electron whistler instabilities waterbag distribution closed-form analytical model cyclotron maser instabilities relativistic plasma arbitrary energy anisotropy anisotropic distribution function dispersion relation electromagnetic wave propagation uniform applied magnetic field }, mynotes={UNREAD}, } @ARTICLE{Trakhtengerts86, author={Trakhtengerts, V.Yu. and Tagirov, V.R. and Chernous, S.A.}, title={ A circulating cyclotron maser and pulsed VLF emissions }, journal={Geomagnetizm i Aeronomiya}, volume={26}, number={1}, year={1986}, month={}, pages={}, abstract={ A theory of a circulating cyclotron maser (CCM) is developed whose basis is a magnetic force tube containing a filament of enhanced plasma concentration; energetic electrons with an anisotropic velocity distribution enter the CCM in the course of magnetic drift, switch on into a cyclotron instability (CI), and emerge from the filament already in depleted form (with an isotropic velocity distribution). The process of connection of new resonant particles as the CI develops (which leads to the pitch regimes of whistler wave generation and the ejection of energetic electrons into the atmosphere) plays an important role. The temporal characteristics of the pitch regime as well as the intensity and spectral characteristics of the ELF and VLF waves excited are found }, keywords={ atmospheric radiation aurora magnetosphere masers plasma plasma instability magnetosphere polar aurora oscillating spots plasma instability circulating cyclotron maser pulsed VLF emissions magnetic force tube filament enhanced plasma concentration energetic electrons anisotropic velocity distribution magnetic drift cyclotron instability connection resonant particles pitch whistler wave generation ejection atmosphere temporal characteristics spectral characteristics ELF }, mynotes={UNREAD}, } @ARTICLE{WingleeAug86, author={Winglee, R.M. and Dulk, G.A.}, title={ The electron-cyclotron maser instability as a source of plasma radiation }, journal={Astrophysical Journal}, volume={307}, number={2}, year={1986}, month={Aug}, pages={808-19}, abstract={ The generation of continuum bursts from the Sun at decimeter and meter wavelengths (in particular, type IV bursts) via the electron-cyclotron maser instability is examined. The maser instability can be driven by an electron distribution with either a loss-cone anisotropy or a peak at large pitch angles. For omega /sub p// Omega /sub e/>>1 the maser emission is produced by electrons interacting through a harmonic (cyclotron) resonance and is electrostatic, being in the upper hybrid mode at frequencies approximately equal to the omega /sub p/. Coalescence processes are required to convert the electrostatic waves into transverse radiation which can escape from the source region. Whether the resultant spectrum is nearly a smooth continuum or has a zebra-stripe pattern, both of which occur in type IV bursts, depends on (a) the form of the electron distribution, (b) inhomogeneities in the density and the magnetic field, and (c) whether the maser reaches saturation }, keywords={ astronomical masers plasma plasma instability solar radiofrequency radiation VHF UHF radio emission electron-cyclotron maser instability plasma radiation continuum bursts Sun electron distribution loss-cone anisotropy pitch angles resonance electrostatic upper hybrid mode transverse radiation zebra-stripe pattern type IV bursts density magnetic field }, mynotes={UNREAD}, } @ARTICLE{PritchettDec86, title={ Cyclotron maser radiation from a source structure localized perpendicular to the ambient magnetic field }, journal={Journal of Geophysical Research}, volume={91}, number={A12}, year={1986}, month={Dec}, pages={13569-81}, abstract={ The plasma cavity in which the auroral kilometric radiation (AKR) is generated is known to contain localized density enhancements, and the cavity itself is surrounded by regions of much higher plasma density. Particle simulations are used to investigate the effects of such a source structure perpendicular to a uniform magnetic field on the generation and propagation of electromagnetic radiation produced by the cyclotron maser instability. It is found that the efficiency of radiation production is significantly increased in comparison to the uniform geometry case. The radiation is observed to consist of wave packets which travel at speeds of the order of 0.1c-0.2c, which is consistent with the X mode group velocity near cutoff. The reflection of these structures at the edge of a density enhancement is quite weak, with less than 0.1% of the incident energy being reflected in a typical case. The radiation with frequency omega 90%) may be possible for the gyro-peniotron. Stable operation requires, however, that mode competition from the electron cyclotron-maser interaction be avoided. This mode competition can be quite serious since the cyclotron-maser start-oscillation currents are generally much smaller than those from the peniotron interaction. The start-oscillation conditions for the peniotron and the electron cyclotron-maser interactions from linear theory are examined. Both large-orbit axis-encircling and small-orbit off-axis electron beams are investigated. Conditions under which a gyro-peniotron oscillator may be operable are presented, including the important limitations on the spread of the beam guiding center. The results indicate that mode competition for the gyro-peniotron can be easily avoided for TE/sub 211/ and other low-order azimuthal modes when a large-orbit axis-encircling beam is used. Serious mode competition and gyropeniotron suppression are found for small-orbit off-axis beams }, keywords={ masers microwave generation microwave oscillators microwave tubes gyro-peniotron oscillator mode competition electron cyclotron-maser interaction electron beams }, mynotes={UNREAD}, } @ARTICLE{WingleeOct85, title={ Fundamental and harmonic electron cyclotron maser emission }, journal={Journal of Geophysical Research}, volume={90}, number={A10}, year={1985}, month={Oct}, pages={9663-74}, abstract={ Auroral kilometric radiation has been attributed to an electron cyclotron maser instability and is known to have components at both the cyclotron frequency and its harmonics. Solar microwave spike bursts and similar bursts from flare stars are also thought to be maser emission at harmonics of the cyclotron frequency. Fundamental X mode growth is known to dominate when omega /sub p// Omega /sub e/ omega /sub p//sup 2// Omega /sub e//sup 2/<<1. Under such conditions, relativistic effects on the dispersion of extraordinary-mode waves near the electron cyclotron frequency are found to be very significant. Linear theory and computer simulation applied to a model distribution indicate that a k/sub ///=0 extraordinary mode with Re omega 6 keV) electron data from the SEEP payload on the low altitude ( approximately 200 km) polar orbiting S81-1 satellite indicate a high rate of occurrence of short duration (<0.6 s) electron precipitation bursts. Characteristics of events observed at night (2230 MLT) versus daytime (1030 MLT) and at midlatitudes (23) were distinctly different in several ways. Comparison of the electron data with simultaneous VLF wave data from Palmer (L approximately=2.4) and Siple (L approximately=4.3) stations in Antarctica indicated a varying degree of association of electron bursts with whistlers and chorus emissions. Several of the electron bursts observed at nighttime and at 23) were observed on satellite passes within +or-50 degrees of the Siple meridian, chorus was invariably detected at Siple, but correlation of electron bursts with individual chorus spectral elements was not evident }, keywords={ atmospheric electron precipitation whistlers radiowave emission magnetosphere ionosphere short-duration electron precipitation bursts VLF wave activity whistlers chorus lightning-generated }, mynotes={UNREAD}, } @ARTICLE{InanFeb89, author={Inan, U.S. and Walt, M. and Voss, H.D. and Imhof, W.L.}, title={ Energy spectra and pitch angle distributions of lightning-induced electron precipitation: analysis of an event observed on the S81-1 (SEEP) satellite }, journal={Journal of Geophysical Research}, volume={94}, number={A2}, year={1989}, month={Feb}, pages={1379-401}, abstract={ Temporal and spectral signatures of a lightning-induced electron precipitation (LEP) burst observed on the S81-1 (SEEP) satellite are analyzed and compared with the predictions of a test particle model of the gyroresonant whistler-particle interaction in the magnetosphere. The flux to be detected by specific detectors on the low altitude ( approximately 220 km) satellite at L approximately=2.24 is calculated in terms of the integral counting rate as a function of time and in terms of the dynamic energy spectra during the initial approximately 300-ms precipitation pulse. For a whistler wave packet with frequency range 500 Hz to 6 kHz the dynamic energy spectra are found to depend sensitively on the electron angular distribution in the vicinity of the loss cone. In the case of a whistler wave originating in northern hemisphere lightning the maximum whistler-induced pitch angle scattering of electrons occurs near approximately 10 degrees S geomagnetic latitude }, keywords={ atmospheric electron precipitation ionosphere magnetosphere ionosphere wave particle interaction pitch angle distributions lightning-induced electron precipitation burst test particle model gyroresonant whistler-particle interaction magnetosphere whistler wave }, mynotes={UNREAD}, } @ARTICLE{ImhofAug86, author={Imhof, W.L. and Voss, H.D. and Walt, M. and Gaines, E.E. and Mobilia, J. and Datlowe, D.W. and Reagen, J.B.}, title={ Slot region electron precipitation by lightning, VLF chorus and plasmaspheric hiss }, journal={Journal of Geophysical Research}, volume={91}, number={A8}, year={1986}, month={Aug}, pages={8883-94}, abstract={ Energetic electrons are precipitated from the slot region of the radiation belts by a variety of mechanisms, including short duration wave bursts associated with lightning and chorus and more slowly varying plasmaspheric hiss. Characteristics of the nightside short duration precipitation events, including their favored occurrence at certain longitudes in the Northern Hemisphere, indicate that they are predominantly associated with lightning. The dayside events seem to relate primarily to VLF chorus. A study is made of various characteristics of the short duration precipitation burst, namely, the longitude and L shell variations, the day/night differences, the energies of spectral maxima and the rapid spectral variations with time. In addition, the total loss rates of electrons from the radiation belts are obtained from the measured energy spectra and pitch angle distributions. An assessment is made of the relative importance of the bursts as a loss mechanism for slot region electrons in comparison to the more slowly varying precipitation processes }, keywords={ atmospheric electron precipitation atmospheric radiation atmospherics lightning magnetosphere radiation belts magnetosphere atmosphere atmospherics radiation electron precipitation lightning VLF chorus plasmaspheric hiss slot region radiation belts short duration wave bursts nightside Northern Hemisphere longitude spectral maxima total loss rates energy spectra pitch angle }, mynotes={UNREAD}, } @ARTICLE{VossDec84, author={Voss, H.D. and Imhof, W.L. and Walt, M. and Mobilia, J. and Gaines, E.E. and Reagan, J.B. and Inan, U.S. and Helliwell, R.A. and Carpenter, D.L. and Katsufrakis, J.P. and Chang, H.C.}, title={ Lightning-induced electron precipitation }, journal={Nature}, volume={312}, number={5996}, year={1984}, month={Dec}, pages={740-2}, abstract={ The authors report the first satellite measurements of electron precipitation induced by lightning. The measured energy deposition of these conspicuous lightning-induced electron precipitation (LEP) bursts ( approximately 10/sup -3/ erg cm/sup -2/) is sufficient to deplete the Earth's radiation belts and to alter subionospheric radiowave propagation (6 keV) electron data from the SEEP payload on the low altitude ( approximately 200 km) polar orbiting S81-1 satellite indicate a high rate of occurrence of short duration (<0.6 s) electron precipitation bursts. Characteristics of events observed at night (2230 MLT) versus daytime (1030 MLT) and at midlatitudes (23) were distinctly different in several ways. Comparison of the electron data with simultaneous VLF wave data from Palmer (L approximately=2.4) and Siple (L approximately=4.3) stations in Antarctica indicated a varying degree of association of electron bursts with whistlers and chorus emissions. Several of the electron bursts observed at nighttime and at 23) were observed on satellite passes within +or-50 degrees of the Siple meridian, chorus was invariably detected at Siple, but correlation of electron bursts with individual chorus spectral elements was not evident }, keywords={ atmospheric electron precipitation whistlers radiowave emission magnetosphere ionosphere short-duration electron precipitation bursts VLF wave activity whistlers chorus lightning-generated }, mynotes={UNREAD}, } @ARTICLE{InanFeb89, author={Inan, U.S. and Walt, M. and Voss, H.D. and Imhof, W.L.}, title={ Energy spectra and pitch angle distributions of lightning-induced electron precipitation: analysis of an event observed on the S81-1 (SEEP) satellite }, journal={Journal of Geophysical Research}, volume={94}, number={A2}, year={1989}, month={Feb}, pages={1379-401}, abstract={ Temporal and spectral signatures of a lightning-induced electron precipitation (LEP) burst observed on the S81-1 (SEEP) satellite are analyzed and compared with the predictions of a test particle model of the gyroresonant whistler-particle interaction in the magnetosphere. The flux to be detected by specific detectors on the low altitude ( approximately 220 km) satellite at L approximately=2.24 is calculated in terms of the integral counting rate as a function of time and in terms of the dynamic energy spectra during the initial approximately 300-ms precipitation pulse. For a whistler wave packet with frequency range 500 Hz to 6 kHz the dynamic energy spectra are found to depend sensitively on the electron angular distribution in the vicinity of the loss cone. In the case of a whistler wave originating in northern hemisphere lightning the maximum whistler-induced pitch angle scattering of electrons occurs near approximately 10 degrees S geomagnetic latitude }, keywords={ atmospheric electron precipitation ionosphere magnetosphere ionosphere wave particle interaction pitch angle distributions lightning-induced electron precipitation burst test particle model gyroresonant whistler-particle interaction magnetosphere whistler wave }, mynotes={UNREAD}, } @ARTICLE{ImhofAug86, author={Imhof, W.L. and Voss, H.D. and Walt, M. and Gaines, E.E. and Mobilia, J. and Datlowe, D.W. and Reagen, J.B.}, title={ Slot region electron precipitation by lightning, VLF chorus and plasmaspheric hiss }, journal={Journal of Geophysical Research}, volume={91}, number={A8}, year={1986}, month={Aug}, pages={8883-94}, abstract={ Energetic electrons are precipitated from the slot region of the radiation belts by a variety of mechanisms, including short duration wave bursts associated with lightning and chorus and more slowly varying plasmaspheric hiss. Characteristics of the nightside short duration precipitation events, including their favored occurrence at certain longitudes in the Northern Hemisphere, indicate that they are predominantly associated with lightning. The dayside events seem to relate primarily to VLF chorus. A study is made of various characteristics of the short duration precipitation burst, namely, the longitude and L shell variations, the day/night differences, the energies of spectral maxima and the rapid spectral variations with time. In addition, the total loss rates of electrons from the radiation belts are obtained from the measured energy spectra and pitch angle distributions. An assessment is made of the relative importance of the bursts as a loss mechanism for slot region electrons in comparison to the more slowly varying precipitation processes }, keywords={ atmospheric electron precipitation atmospheric radiation atmospherics lightning magnetosphere radiation belts magnetosphere atmosphere atmospherics radiation electron precipitation lightning VLF chorus plasmaspheric hiss slot region radiation belts short duration wave bursts nightside Northern Hemisphere longitude spectral maxima total loss rates energy spectra pitch angle }, mynotes={UNREAD}, } @ARTICLE{VossDec84, author={Voss, H.D. and Imhof, W.L. and Walt, M. and Mobilia, J. and Gaines, E.E. and Reagan, J.B. and Inan, U.S. and Helliwell, R.A. and Carpenter, D.L. and Katsufrakis, J.P. and Chang, H.C.}, title={ Lightning-induced electron precipitation }, journal={Nature}, volume={312}, number={5996}, year={1984}, month={Dec}, pages={740-2}, abstract={ The authors report the first satellite measurements of electron precipitation induced by lightning. The measured energy deposition of these conspicuous lightning-induced electron precipitation (LEP) bursts ( approximately 10/sup -3/ erg cm/sup -2/) is sufficient to deplete the Earth's radiation belts and to alter subionospheric radiowave propagation (130 km for the most perturbed case with larger enhancements in selected narrower spectral regions. The predicted IR enhancements should be observable to an orbiting IR sensor }, keywords={ atmospheric electricity atmospheric radiation atmospheric temperature carbon compounds thunderstorms infrared glow thunderstorms heating lower ionospheric electrons CO/sub 2/ emission excitation rate electron collisions steady-state two-dimensional electrostatic-heating upward coupling vibrational energy transfer line-by-line nonLTE limb-viewing radiance profiles charge distributions ambient ionic conductivities tangent heights 4.3 mum N/sub 2/ CO/sub 2/ }, mynotes={UNREAD}, } @ARTICLE{SonwalkarJul97, author={Sonwalkar, V.S. and Carpenter, D.L. and Helliwell, R.A. and Walt, M. and Inan, U.S. and Caudle, D.L. and Ikeda, M.}, title={ Properties of the magnetospheric hot plasma distribution deduced from whistler mode wave injection at 2400 Hz: ground-based detection of azimuthal structure in magnetospheric hot plasmas }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14363-80}, abstract={ Siple station VLF wave injection experiments aimed at finding the properties of the magnetospheric hot plasma were conducted for a 9-hour period between 1705 and 0210 UT on January 23-24, 1988. A special frequency versus time format, lasting 1 min and transmitted every 5 min, consisted of a sequence of pulses, frequency ramps, and parabolas, all in a 1-kHz range centered on 2400 Hz. The transmitted signals, after propagating along a geomagnetic field-aligned duct were recorded at Lake Mistissini, Canada. At various times during the 9-hour interval the Siple signals showed features characteristic of wave-particle interactions, including wave growth, sidebands, and triggered emissions. On the assumption that gyroresonant interactions were responsible for the observed wave growth and saturation, the timescales over which those phenomena varied provide constraints on the possible energetic electron population within the duct. The authors conclude that ground-based active and passive wave experiments have substantial potential for investigating properties of the hot plasma of the magnetosphere }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation magnetospheric hot plasma distribution whistler mode wave injection ground-based detection azimuthal structure Siple station VLF wave injection experiments AD 1988 01 23 to 24 geomagnetic field-aligned duct Siple signals wave-particle interactions wave growth sidebands triggered emissions gyroresonant interactions energetic electron population ground-based active experiments passive wave experiments 2400 Hz }, mynotes={UNREAD}, } @ARTICLE{CarpenterJul97, author={Carpenter, D.L. and Sonwalkar, V.S. and Helliwell, R.A. and Walt, M. and Inan, U.S. and Ikeda, M. and Caudle, D.L.}, title={ Probing properties of the magnetospheric hot plasma distribution by whistler mode wave injection at multiple frequencies: evidence of spatial as well as temporal wave growth }, journal={Journal of Geophysical Research}, volume={102}, number={A7}, year={1997}, month={Jul}, pages={14355-62}, abstract={ Discusses and illustrates the use of wave injection at multiple discrete frequencies to study temporal changes in magnetospheric hot electrons with parallel (gyroresonant) velocities in various nonoverlapping ranges. The data studied were acquired during a special 9-hour period of 1.9-2.9 kHz VLF transmissions from Siple Station, Antarctica, to Lake Mistissini, Canada, on January 23-24, 1988. The amplitudes of the leading edges of constant frequency pulses at 1900, 2150, and 2400 Hz were found to vary independently with time. This is interpreted as evidence of a spatial amplification process that accompanied the well known and more readily identifiable phenomena of exponential temporal growth to a saturation level. Evidence of wave-hot plasma interactions showed a dependence on df/dt of the input signal frequency versus time format; in general, the slow frequency ramps showed the highest amplitudes and the fast ramps and parabolas the lowest, in agreement with past work }, keywords={ magnetospheric electromagnetic wave propagation plasma plasma waves whistlers magnetospheric hot plasma distribution whistler mode wave injection spatial wave growth temporal wave growth wave injection multiple frequencies temporal changes magnetospheric hot electrons gyroresonant velocities VLF transmissions Siple Station AD 1988 01 23 to 24 spatial amplification process wave-hot plasma interactions 1.9 to 2.9 kHz }, mynotes={UNREAD}, } @ARTICLE{PaskoJul97, author={Pasko, V.P. and Inan, U.S. and Bell, T.F.}, title={ Sprites as evidence of vertical gravity wave structures above mesoscale thunderstorms }, journal={Geophysical Research Letters}, volume={24}, number={14}, year={1997}, month={Jul}, pages={1735-8}, abstract={ Large area multicell thunderstorms lead to the formation of vertically oriented cylindrical structures of gravity waves at mesospheric altitudes closely resembling those observed in optical emissions associated with transient luminous glows called sprites }, keywords={ atmospheric movements gravity waves lightning mesosphere thunderstorms lightning mesosphere middle atmosphere movement gravity wave vertically oriented cylindrical structure sprite sprites vertical gravity wave structure mesoscale thunderstorm optical emission optical emissions transient luminous glow model penetrative convection mesoscale convective complex }, mynotes={UNREAD}, } @ARTICLE{CummerJul97, author={Cummer, S.A. and Inan, U.S.}, title={ Measurement of charge transfer in sprite-producing lightning using ELF radio atmospherics }, journal={Geophysical Research Letters}, volume={24}, number={14}, year={1997}, month={Jul}, pages={1731-4}, abstract={ Transient high altitude optical emissions referred to as "sprites" are believed to occur as a result of the transfer of large amounts of charge (\100-300 C) from cloud altitudes of 5-10 km to the ground. Using a general subionospheric ELF propagation model, the authors quantitatively interpret magnetic field waveforms of ELF radio atmospherics originating in mid-western U.S. lightning discharges and observed at Stanford (\1800 km range) to determine the temporal variation of the lightning current and thereby measure the charge transfer during the stroke. For 6 sprite-producing lightning current waveforms observed on July 24, 1996, the authors find that 25 to 325 coulombs of charge was transferred during the first 5 ms of the discharges, assuming a 10 km altitude for the initial charge }, keywords={ atmospherics clouds ionospheric electromagnetic wave propagation lightning thunderstorms atmosphere troposphere thunderstorm thundercloud electric current electric charge transfer sprite-producing lightning sprites ELF radio atmospherics transient high altitude optical emission cloud subionospheric ELF propagation model magnetic field waveform United States USA temporal variation lightning current AD 1996 07 24 }, mynotes={UNREAD}, } @ARTICLE{CummerApr97, author={Cummer, S.A. and Bell, T.F. and Inan, U.S. and Chenette, D.L.}, title={ VLF remote sensing of high-energy auroral particle precipitation }, journal={Journal of Geophysical Research}, volume={102}, number={A4}, year={1997}, month={Apr}, pages={7477-84}, abstract={ Ground-based measurements of VLF transmitter signals propagating in the Earth-ionosphere waveguide can be used to determine the location of nighttime high-energy (>or approximately=100 keV) auroral particle precipitation. When the region of auroral particle precipitation passes over a VLF propagation path, disturbances in the D-region of the ionosphere created by the high-energy particles perturb the amplitude of VLF signals propagating below in a characteristic manner. Continuous nighttime observations of the amplitude of the signal from the NLK transmitter (24.8 kHz, Jim Creek, Washington) were made in Gander, Newfoundland, during November 1993 and January 1994. Simultaneous images of atmospheric X-rays created by auroral particle precipitation taken by the AXIS instrument on the UARS satellite were examined for times when large-scale auroral particle precipitation extended over the NLK-Gander propagation path. Quantitative characteristics of the precipitation-associated NLK signal perturbations are established from days which clearly exhibit good correlation between the AXIS images and VLF data, and a larger data set from the months of November 1993 and January 1994 is examined statistically to determine the effectiveness of the VLF technique in capturing particle precipitation events. The number of particle precipitation onsets seen in the AXIS images that can be readily identified in the VLF amplitude data is found to be almost 94%. VLF propagation model calculations show that the observed VLF amplitude decreases are consistent with propagation under conditions of enhanced lower ionosphere electron density caused by auroral electron precipitation and suggest that electrons with energies greater than 100 keV are responsible for the VLF amplitude perturbations }, keywords={ atmospheric electron precipitation atmospheric ion precipitation ionospheric techniques ionosphere measurement technique radiowave propagation VLF remote sensing high-energy auroral particle precipitation electron precipitation VLF transmitter signal Earth-ionosphere waveguide location nighttime high-energy precipitation D-region NLK transmitter USA Washington Newfoundland Canada Gander AD 1993 AD 1994 signal perturbation VLF technique ion precipitation 24.8 kHz }, mynotes={UNREAD}, } @ARTICLE{PaskoMar97, author={Pasko, V.P. and Inan, U.S. and Bell, T.F. and Taranenko, Y.N.}, title={ Sprites produced by quasi-electrostatic heating and ionization in the lower ionosphere }, journal={Journal of Geophysical Research}, volume={102}, number={A3}, year={1997}, month={Mar}, pages={4529-61}, abstract={ Quasi-electrostatic (QE) fields that temporarily exist at high altitudes following the sudden removal (e.g., by a lightning discharge) of thundercloud charge at low altitudes lead to ambient electron heating (up to \5 eV average energy), ionization of neutrals, and excitation of optical emissions in the mesosphere/lower ionosphere. Model calculations predict the possibility of significant (several orders of magnitude) modification of the lower ionospheric conductivity in the form of depletions of electron density due to dissociative attachment to O/sub 2/ molecules and/or in the form of enhancements of electron density due to breakdown ionization. Results indicate that the optical emission intensities of the 1st positive band of N/sub 2/ corresponding to fast (\1 ms) removal of 100-300 degrees C of thundercloud charge from 10 km altitude are in good agreement with observations of the upper part ("head" and "hair" [Sentman et al., 1995]) of the sprites. The typical region of brightest optical emission has horizontal and vertical dimensions \10 km, centered at altitudes 70 km and is interpreted as the head of the sprite. The model also shows the formation of low intensity glow ("hair") above this region due to the excitation of optical emissions at altitudes \85 km during \500 mu s at the initial stage of the lightning discharge. Comparison of the optical emission intensities of the 1st and 2nd positive bands of N/sub 2/, Meinel and 1st negative bands of N/sub 2//sup +/ and 1st negative band of O/sub 2//sup +/ demonstrates that the 1st positive band of N/sub 2/ is the dominating optical emission in the altitude range around \70 km, which accounts for the observed red color of sprites, in excellent agreement with recent spectroscopic observations of sprites. Results indicate that the optical emission levels are predominantly defined by the lightning discharge duration and the conductivity properties of the atmosphere/lower ionosphere (i.e., relaxation time of electric }, keywords={ airglow atmospheric ionisation ionosphere ionospheric disturbances lightning mesosphere stratosphere thunderstorms thunderstorm lightning mesosphere ionosphere optical emission airglow middle atmosphere quasi-electrostatic heating sprite ionization electron heating model calculation breakdown ionization ionospheric disturbance thundercloud charge head hair red color }, mynotes={UNREAD}, } @ARTICLE{InanMar97, author={Inan, U.S. and Barrington-Leigh, C. and Hansen, S. and Glukhov, V.S. and Bell, T.F. and Rairden, R.}, title={ Rapid lateral expansion of optical luminosity in lightning-induced ionospheric flashes referred to as elves' }, journal={Geophysical Research Letters}, volume={24}, number={5}, year={1997}, month={Mar}, pages={583-6}, abstract={ Data acquired by a new array of horizontally spaced photometers boresighted with a low-light-level camera provide the first measurement of the rapid lateral expansion of optical luminosity in lightning-induced ionospheric flashes referred to as elves', occurring over time scales substantially less than 1 ms. The narrow individual fields-of-view of (2.2 degrees *1.1 degrees ) provide a spatial resolution of \20-km at a range of 500 km, enabling the documentation of expansion occurring over a horizontal range of 200 km with a time resolution of \30 mu s. The observed dynamic features of elves are consistent with a model in which the optical output is produced as a result of heating by the electromagnetic pulse (EMP) from a lightning discharge }, keywords={ atmospheric radiation atmospheric temperature ionospheric disturbances lightning plasma radiofrequency heating rapid lateral expansion optical luminosity lightning-induced ionospheric flashes elves dynamic features heating electromagnetic pulse lightning discharge }, mynotes={UNREAD}, } @ARTICLE{CarpenterJan97, author={Carpenter, D.L. and Galand, M. and Bell, T.F. and Sonwalkar, V.S. and Inan, U.S. and LaBelle, J. and Smith, A.J. and Clark, T.D.G. and Rosenberg, T.J.}, title={ Quasiperiodic \5-60 s fluctuations of VLF signals propagating in the Earth-ionosphere waveguide: a result of pulsating auroral particle precipitation? }, journal={Journal of Geophysical Research}, volume={102}, number={A1}, year={1997}, month={Jan}, pages={347-61}, abstract={ Subionospheric very low frequency and low-frequency (VLF/LF) transmitter signals received at middle-latitude ground stations at nighttime were found to exhibit pulsating behavior with periods that were typically in the \5-60 s range but sometimes reached \100 s. The amplitude versus time shape of the pulsations was often triangular or zigzag-like, hence the term "zigzag effect." Variations in the envelope shape were usually in the direction of faster development than recovery. Episodes of zigzag activity at Siple, Antarctica (L\4.3), and Saskatoon, Canada (L\4.2), were found to occur widely during the predawn hours and were not observed during geomagnetically quiet periods. The fluctuations appeared to be caused by ionospheric perturbations at the \85 km nighttime VLF reflection height in regions poleward of the plasmapause. The authors infer that in the case of the Saskatoon and Siple data, the perturbations were centered within \500 km of the stations and within \100-200 km of the affected signal paths. Their horizontal extent is inferred to have been in the range \50-200 km. The assembled evidence, supported by Corcuff's (1996) research at Kerguelen (L\3.7), suggests that the underlying cause of the effect was pulsating auroral precipitation }, keywords={ atmospheric elementary particle precipitation Earth-ionosphere waveguide radiowave propagation quasiperiodic fluctuations VLF signals Earth-ionosphere waveguide pulsating auroral particle precipitation subionospheric LF transmitter signals zigzag effect envelope shape Siple Antarctica Saskatoon Canada ionospheric perturbations nighttime VLF reflection height 5 to 60 s }, mynotes={UNREAD}, } @ARTICLE{ReisingDec96, author={Reising, S.C. and Inan, U.S. and Bell, T.F. and Lyons, W.A.}, title={ Evidence for continuing current in sprite-producing cloud-to-ground lightning }, journal={Geophysical Research Letters}, volume={23}, number={24}, year={1996}, month={Dec}, pages={3639-42}, abstract={ Radio atmospherics launched by sprite-producing positive cloud-to-ground lightning flashes and observed at Palmer Station, Antarctica, exhibit large ELF slow tails following the initial VLF portion, indicating the presence of continuing currents in the source lightning flashes. One-to-one correlation of sferics with NLDN lightning data in both time and arrival azimuth, measured with an accuracy of +or-1 degrees at \12,000 km range, allows unambiguous identification of lightning flashes originating in the storm of interest. Slow-tail measurements at Palmer can potentially be used to measure continuing currents in lightning flashes over nearly half of the Earth's surface }, keywords={ atmospherics lightning thunderstorms atmosphere troposphere electric field electric current continuing current sprite-producing cloud-to-ground lightning thunderstorm atmospherics positive cloud-to-ground lightning flash Palmer Station Antarctica large ELF slow tail source lightning flash sferics NLDN lightning }, mynotes={UNREAD}, } @ARTICLE{LehtinenSep96, author={Lehtinen, N.G. and Walt, M. and Inan, U.S. and Bell, T.F. and Pasko, V.P.}, title={ gamma -ray emission produced by a relativistic beam of runaway electrons accelerated by quasi-electrostatic thundercloud fields }, journal={Geophysical Research Letters}, volume={23}, number={19}, year={1996}, month={Sep}, pages={2645-8}, abstract={ In an experiment described by Fishman et al. [1994], high energy photons of atmospheric origin were detected by the Burst and Transient Source Experiment (BATSE) detectors, located on the Compton Gamma Ray Observatory (CGRO). In this paper the authors assess the possibility that the bursts may be bremsstrahlung produced by relativistic (>1 MeV) runaway electron beams-accelerated in an avalanche process by quasi-electrostatic thundercloud fields. They consider the height-dependent density profile of the relativistic electrons specified as a function of time in the context of a previously reported runaway model [Bell et al., 1995]. The electron beam is modeled as a vertical cylinder with radius 10 km, and numerical estimates are provided of gamma -ray fluxes which would be observed at the satellite. The predicted fluxes at the satellite altitude and at horizontal distances of up to 500 km from the source are found to be comparable to the experimental data }, keywords={ atmospheric electricity atmospheric radiation gamma-rays lightning thunderstorms atmosphere storm thunderstorm gamma ray emission gamma -ray emission relativistic electron beam runaway electrons quasi-electrostatic field electric field lightning high energy photons BATSE CGRO gamma ray burst bremsstrahlung avalanche process relativistic electrons runaway model vertical cylinder gamma -ray flux }, mynotes={UNREAD}, } @ARTICLE{FukunishiAug96, author={Fukunishi, H. and Takahashi, Y. and Kubota, M. and Sakanoi, K. and Inan, U.S. and Lyons, W.A.}, title={ Elves: lightning-induced transient luminous events in the lower ionosphere }, journal={Geophysical Research Letters}, volume={23}, number={16}, year={1996}, month={Aug}, pages={2157-60}, abstract={ Observations of optical phenomena at high altitude above thunderstorms using a multichannel high-speed photometer and image intensified CCD cameras were carried but at Yucca Ridge Field Station (40 degrees 40' N, 104 degrees 56' W), Colorado as part of the SPRITES'95 campaign from 15 June to August 6, 1995. These new measurements indicate that diffuse optical flashes with a duration of <1 ms and a horizontal scale of À100-300 km occur at 75-105 km altitude in the lower ionosphere just after the onset of cloud-to-ground lightning discharges, but preceding the onset of sprites. Here we designate these events as "elves" to distinguish them from "red sprites". This finding is consistent with the production of diffuse optical emissions due to the heating of the lower ionosphere by electromagnetic pulses generated by lightning discharges as suggested by several authors }, keywords={ atmospheric radiation atmospheric temperature electromagnetic pulse ionospheric disturbances lightning thunderstorms lightning-induced transient luminous events lower ionosphere thunderstorms SPRITES'95 campaign diffuse optical flashes cloud-to-ground lightning discharges elves heating electromagnetic pulses AD 1995 06 15 to 08 06 75 to 105 km }, mynotes={UNREAD}, } @ARTICLE{GlukhovAug96, author={Glukhov, V.S. and Inan, U.S.}, title={ Particle simulation of the time-dependent interaction with the ionosphere of rapidly varying lightning EMP }, journal={Geophysical Research Letters}, volume={23}, number={16}, year={1996}, month={Aug}, pages={2193-6}, abstract={ The interaction with the lower ionosphere of rapidly varying electromagnetic pulses (EMPs) produced by lightning discharges is studied. The nonlinear heating, ionization and optical emission production are modeled using the Monte Carlo technique, which allows for consideration of realistic lightning EMPs with a few mu s rise times. Results indicate that the electron distribution function is highly anisotropic during the first few mu s of the interaction, but subsequently develops into a near-isotropic quasi-stationary state. The peak optical emissions intensities are found to be highly dependent on the EMP waveform, while the altitude range at which the emissions occur is relatively independent of pulse shape. Results of the particle simulation are used to assess the range of applicability of the quasi-stationary models [Taranenko et al., 1993; Inan et al., 1996] }, keywords={ electromagnetic pulse ionospheric disturbances ionospheric electromagnetic wave propagation lightning EM pulse radiowave propagation ionospheric disturbance particle simulation time-dependent interaction ionosphere rapidly varying lightning EMP rapidly varying electromagnetic pulse nonlinear heating ionization optical emission Monte Carlo method anisotropic electron distribution function EMP waveform quasistationary model }, mynotes={UNREAD}, } @ARTICLE{Lev-TovJul96, author={Lev-Tov, S.J. and Inan, U.S. and Smith, A.J. and Clilverd, M.A.}, title={ Characteristics of localized ionospheric disturbances inferred from VLF measurements at two closely spaced receivers }, journal={Journal of Geophysical Research}, volume={101}, number={A7}, year={1996}, month={Jul}, pages={15737-47}, abstract={ The very low frequency (VLF) NPM signal from Hawaii was recorded at two closely spaced (À50 km) receivers (located at Palmer and Faraday stations) on the Antarctic Peninsula. Measurements of characteristic amplitude and phase signatures of lightning-induced electron precipitation (LEP) events were made on three different days in March 1992. Both amplitude and, for the first time, phase measurements are quantitatively interpreted using a three-dimensional model of VLF propagation in the Earth-ionosphere waveguide in the presence of lower ionospheric disturbances. This is the first time such a study has been undertaken with mirrored precipitation. Differences between the amplitude and phase changes at the two sites are accounted for by the location of the LEP ionospheric disturbance transverse to the VLF signal propagation paths. The change in these differences is explained by the horizontal movement of the disturbance region and, therefore, the causative whistler duct footprint across the transmitter-receiver paths. Trends in the amplitude and phase changes on a timescale of order 1 hour are found to be encompassed by the modeling of the passage of the day-night terminator along the paths }, keywords={ atmospheric electron precipitation Earth-ionosphere waveguide ionospheric disturbances ionosphere three-dimensional model AD 1992 03 localized ionospheric disturbance VLF two closely spaced receivers Antarctica amplitude phase signatures lightning-induced electron precipitation radiowave propagation Earth-ionosphere waveguide mirrored precipitation causative whistler duct footprint transmitter-receiver path day-night terminator passage }, mynotes={UNREAD}, } @ARTICLE{InanMay96, author={Inan, U.S. and Pasko, V.P. and Bell, T.F.}, title={ Sustained heating of the ionosphere above thunderstorms as evidenced in "early/fast" VLF events }, journal={Geophysical Research Letters}, volume={23}, number={10}, year={1996}, month={May}, pages={1067-70}, abstract={ Quasi-electrostatic (QE) thundercloud fields are proposed to maintain the ionospheric electrons at a persistently heated level well above their ambient thermal energy. Changes in the thundercloud charge (e.g., in lightning discharges) lead to heating/cooling above/below this quiescent level, and are registered as sudden (i.e., fast'<20 ms) subionospheric VLF signal changes, occurring simultaneously (i.e., early'<20 ms) with lightning discharges, and referred to as early/fast VLF events [Inan et al., 1993] }, keywords={ atmospheric radiation atmospheric temperature ionospheric disturbances lightning thunderstorms sustained heating ionosphere thunderstorms VLF events quasi-electrostatic thundercloud fields lightning discharges cooling subionospheric VLF signal changes }, mynotes={UNREAD}, } @ARTICLE{InanMay96, author={Inan, U.S. and Reising, S.C. and Fishman, G.J. and Horack, J.M.}, title={ On the association of terrestrial gamma-ray bursts with lightning and implications for sprites }, journal={Geophysical Research Letters}, volume={23}, number={9}, year={1996}, month={May}, pages={1017-20}, abstract={ Measurements of ELF/VLF radio atmospherics (sterics) at Palmer Station, Antarctica, provide evidence of active thunderstorms near the inferred source regions of two different gamma-ray bursts of terrestrial origin (Fishman et al., 1994). In one case, a relatively intense steric occurring within +or-1.5 ms of the time of the gamma-ray burst provides the first indication of a direct association of this burst with a lightning discharge. This steric and many others launched by positive cloud-to-ground (CG) discharges and observed at Palmer during the periods studied exhibit slow tail' waveforms, indicative of continuing currents in the causative lightning discharges. The slow tails of these sterics are similar to those of sterics originating in positive CG discharges that are associated with sprites }, keywords={ atmospheric radiation atmospherics lightning thunderstorms terrestrial gamma-ray bursts CGRO observations sprites ELF radio atmospherics VLF radio atmospherics sterics Palmer Station Antarctica active thunderstorms source regions lightning discharge positive cloud-to-ground discharges slow tail waveforms 300 Hz to 20 kHz }, mynotes={UNREAD}, } @ARTICLE{PaskoMar96, author={Pasko, V.P. and Inan, U.S. and Bell, T.F.}, title={ Sprites as luminous columns of ionization produced by quasi-electrostatic thundercloud fields }, journal={Geophysical Research Letters}, volume={23}, number={6}, year={1996}, month={Mar}, pages={649-52}, abstract={ Quasi-electrostatic (QE) fields which exist above thunderclouds after lightning discharges can lead to the formation of columnar channels of breakdown ionization and carrot-like vertical luminous structures with typical transverse dimension À5-10 km spanning an altitude range from À80 km to well below À50 km. The carrot-like forms closely resemble those observed in sprites. Results indicate that the appearance of optical emissions can be significantly delayed in time (À1-20 ms) with respect to the causative lightning discharge }, keywords={ airglow atmospheric electricity atmospheric ionisation lightning mesosphere thermosphere thunderstorms middle atmosphere mesosphere upper atmosphere thermosphere stratosphere ionisation ionization sprite thunderstorm disturbance optical emission electric discharge luminous column quasi-electrostatic field electric field lightning columnar channel breakdown ionization carrot-like vertical luminous structure delay }, mynotes={UNREAD}, } @ARTICLE{CummerMar96, author={Cummer, S.A. and Bell, T.F. and Inan, U.S. and Zanetti, L.J.}, title={ VLF remote sensing of the auroral electrojet }, journal={Journal of Geophysical Research}, volume={101}, number={A3}, year={1996}, month={Mar}, pages={5381-9}, abstract={ Investigates a new potential technique to determine the position of the auroral electrojet from ground-based VLF amplitude and phase measurements. The chief advantage of this technique over conventional ground magnetometer measurements is that it can provide data on a continental scale with a small number of receiving stations and with a minimum of data processing. At the edge of the auroral zone, where the electrojet current system flows, high-energy (E>300 keV) precipitating electrons cause local electron density enhancements in the ionosphere which cause phase and amplitude perturbations in VLF waves propagating in the Earth-ionosphere waveguide. Continuous measurements of the amplitude and phase of signals from the Omega North Dakota VLF transmitter were made in Nome, Alaska. Using a two-dimensional model of VLF propagation which accounts for ionospheric disturbances caused by the electron precipitation associated with the electrojet, the amplitude and phase signatures of electrojet incursion across each propagation path were predicted. Seventeen nights of simultaneous VLF amplitude and phase data and ground magnetometer data were examined and catalogued based on the degree of temporal correlation between the two data sets and the degree to which the VLF events matched the propagation simulations. Of the nights exhibiting activity, more than 60% exhibited excellent correlation between the magnetometer and VLF events, and the majority of these showed good agreement with the model results. An additional estimate of the electrojet position was provided for one of the studied sights by field-aligned current measurements from the Freja satellite. A comparison of these independent means of determining the electrojet position shows that they are in good agreement for the night examined }, keywords={ electrojets ionospheric electromagnetic wave propagation ionospheric techniques ionosphere electric current measurement technique ground based method VLF remote sensing auroral electrojet position radiowave amplitude phase Earth-ionosphere waveguide LF propagation electron precipitation }, mynotes={UNREAD}, } @ARTICLE{InanMar96, author={Inan, U.S. and Slingeland, A. and Pasko, V.P. and Rodriguez, J.V.}, title={ VLF and LF signatures of mesospheric/lower ionospheric response to lightning discharges }, journal={Journal of Geophysical Research}, volume={101}, number={A3}, year={1996}, month={Mar}, pages={5219-38}, abstract={ New evidence is presented of disturbances of the electrical conductivity of the nighttime mesosphere and the lower ionosphere in association with lightning discharges. In addition to extensive documentation of the characteristics of a class of events heretofore referred to as early/fast VLF events, Inan et al. (1993), the present authors data reveal a new feature of these events, consisting of a postonset peak that typically lasts for 1-2 s. They also report the observation of short-duration VLF or LF perturbations, in which the amplitude of the subionospheric signal exhibits a sudden change within 20 ms of the causative lightning discharge, and recovers back to its original level in <3 s. These short-duration events have characteristics similar to the previously observed rapid onset, rapid decay VLF signatures, Doulden et al. (1994). Both the typical and rapidly recovering events are observed primarily when the causative lightning discharge is within +or-50 km of the VLF or LF great circle propagation path, indicating that the scattering from the localized disturbance is highly collimated in the forward direction. The latter in turn implies that for the parameters in hand, the transverse extent of the disturbance must be at least À100-150 km. The measured VLF signatures are compared with the predictions of a three-dimensional model of subionospheric VLF propagation and scattering in the presence of localized ionospheric disturbances produced by electromagnetic impulses and quasi-electrostatic QE fields produced by lightning discharges. The rapidly recovering or short-duration events are consistent with the heating of the ambient electrons by quasi-static electric fields, in cases when heating is not intense enough to exceed-the attachment or ionization thresholds. When no significant electron density changes occur, the conductivity changes due to heating alone last only as long as the QE fields, typically less than a few seconds. When heating is intense enough so t }, keywords={ atmospheric electricity atmospheric electromagnetic wave propagation atmospherics ionospheric disturbances ionospheric electromagnetic wave propagation lightning mesosphere atmospherics radiowave emission thunderstorm VLF signature LF signature mesosphere lower ionosphere response middle atmosphere ionospheric disturbance lightning electric discharge electrical conductivity night postonset peak short-duration perturbation short-duration events radiowave propagation }, mynotes={UNREAD}, } @ARTICLE{AlfordJan96, author={Alford, J. and Engebretson, M. and Arnoldy, R. and Inan, U.}, title={ Frequency variations of quasi-periodic ELF-VLF emissions: a possible new ground-based diagnostic of the outer high-latitude magnetosphere }, journal={Journal of Geophysical Research}, volume={101}, number={A1}, year={1996}, month={Jan}, pages={83-97}, abstract={ Magnetic pulsations and quasi-periodic (QP) amplitude modulations of ELF-VLF waves at Pc 3-4 frequencies (15-50 mHz) are commonly observed simultaneously in cusp-latitude data. The naturally occurring ELF-VLF emissions are believed to be modulated within the magnetosphere by the compressional component of geomagnetic pulsations formed external to the magnetosphere. The authors have examined data from South Pole Station (LÀ14) to determine the occurrence and characteristics of QP emissions. On the basis of 14 months of data during 1987 and 1988 they found that QP emissions typically appeared in both the 0.5-1 kHz and 1-2 kHz receiver channels at South Pole Station and occasionally in the 2-4 kHz channel. The QP emission frequency appeared to depend on solar wind parameters and interplanetary magnetic field (IMF) direction, and the months near fall equinox in both 1987 and 1988 showed a significant increase in the percentage of QP emissions only in the lowest-frequency channel. They present a model consistent with these variations in which high-latitude (nonequatorial) magnetic field minima near the magnetopause play a major role, because the field magnitude governs both the frequency of ELF-VLF emissions and the whistler mode propagation cutoffs. Because the field in these regions will be strongly influenced by solar wind and IMF parameters, variations in the frequency of such emissions may be useful in providing ground-based diagnostics of the outer high-latitude magnetosphere }, keywords={ atmospheric radiation atmospheric techniques magnetosphere micropulsations whistlers atmosphere measurement technique outer magnetosphere magnetic pulsation micropulsation radiowave emission frequency variation quasi-periodic ELF-VLF emission quasiperiodic emissions ELF VLF high-latitude magnetosphere magnetic pulsations amplitude modulation Pc 3 Pc 4 geomagnetic pulsations South Pole Station occurrence characteristics AD 1987 AD 1988 interplanetary magnetic field IMF direction whistler mode propagation cutoff 0.5 to 5 kHz }, mynotes={UNREAD}, } @ARTICLE{PaskoFeb96, author={Pasko, V.P. and Inan, U.S. and Bell, T.F.}, title={ Blue jets produced by quasi-electrostatic pre-discharge thundercloud fields }, journal={Geophysical Research Letters}, volume={23}, number={3}, year={1996}, month={Feb}, pages={301-4}, abstract={ Pre-discharge quasi-electrostatic fields immediately above the thundercloud lead to the formation and upward propagation of streamer type ionization channels with features in good agreement with video observations of blue jets }, keywords={ atmospheric electricity electric fields lightning thunderstorms blue jets quasielectrostatic predischarge thundercloud fields upward propagation formation streamer type ionization channels video observations sprites runaway electrons 100 km/s }, mynotes={UNREAD}, } @ARTICLE{InanJan96, author={Inan, U.S. and Sampson, W.A. and Taranenko, Y.N.}, title={ Space-time structure of optical flashes and ionization changes produced by lightning-EMP }, journal={Geophysical Research Letters}, volume={23}, number={2}, year={1996}, month={Jan}, pages={133-6}, abstract={ Intense electromagnetic pulses (EMPs) released by lightning discharges produce bright optical emissions at 80-95 km altitudes emitted in a thin (À30 km) cylindrical shell expanding to radial distances of up to >150 km, lasting for À400 mu s, and appearing in limb-view as a thin layer with À400 km lateral extent }, keywords={ airglow atmospheric ionisation atmospheric optics atmospheric radiation lightning upper atmosphere airglow optical emission thermosphere spatial structure temporal structure optical flash light ionization change lightning EMP electromagnetic pulse EM pulse thin cylindrical shell 80 to 95 km }, mynotes={UNREAD}, } @ARTICLE{InanDec95, author={Inan, U.S. and Bell, T.F. and Pasko, V.P. and Sentman, D.D. and Wescott, E.M. and Lyons, W.A.}, title={ VLF signatures of ionospheric disturbances associated with sprites }, journal={Geophysical Research Letters}, volume={22}, number={24}, year={1995}, month={Dec}, pages={3461-4}, abstract={ VLF perturbations on signals propagating along great-circle-paths (GCP) through electrically active midwest thunderstorms are associated with luminous high altitude glows (referred to as sprites) observed from aircraft or ground. The data constitutes the first evidence that the physical processes leading to sprites also alter the conductivity of the lower ionosphere }, keywords={ airglow ionosphere ionospheric disturbances ionospheric electromagnetic wave propagation lightning mesosphere radiowave propagation thermosphere thunderstorms upper atmosphere ionosphere mesosphere upper atmosphere middle atmosphere VLF signature ionospheric disturbance sprite lightning airglow great-circle-path electrically active midwest thunderstorm United States USA radiowave propagation luminous high altitude glow sprites lower ionosphere electrical conductivity decrease }, mynotes={UNREAD}, } @ARTICLE{Lev-TovNov95, author={Lev-Tov, S.J. and Inan, U.S. and Bell, T.F.}, title={ Altitude profiles of localized D region density disturbances produced in lightning-induced electron precipitation events }, journal={Journal of Geophysical Research}, volume={100}, number={A11}, year={1995}, month={Nov}, pages={21375-83}, abstract={ A three-dimensional model of very low frequency (VLF) radio wave propagation in the Earth-ionosphere waveguide in the presence of lower ionospheric disturbances is used to quantitatively interpret VLF signatures of lightning-induced electron precipitation (LEP) events observed in two previously reported cases. One case is that of a 28.5-kHz signal originating in Puerto Rico and propagating to a receiver in Lake Mistissini, Quebec. The other case involves a 24.0-kHz signal originating in Cutler, Maine, and received at Stanford, California. In both cases, high-resolution measurements of the VLF signals were made to accurately document characteristic signatures of LEP events. The comparison of the model calculations with the data yields information about the altitude profiles of electron density of both the extra ionization produced by the LEP events and of the ambient ionospheric D-region. The comparisons are carried out using generally accepted values of the spatial extent of the disturbed regions and the intensity of the particle flux constituting the LEP burst }, keywords={ atmospheric electron precipitation D-region Earth-ionosphere waveguide electron density ionospheric disturbances lightning radiowave propagation ionosphere localized D-region density disturbances lightning-induced electron precipitation events altitude profiles 3D model VLF radio wave propagation Earth-ionosphere waveguide lower ionospheric disturbances high-resolution measurements LEP events electron density ionization disturbed regions particle flux intensity 28.5 kHz 24 kHz }, mynotes={UNREAD}, } @ARTICLE{BellAug95, author={Bell, T.F. and Pasko, V.P. and Inan, U.S.}, title={ Runaway electrons as a source of red sprites in the mesosphere }, journal={Geophysical Research Letters}, volume={22}, number={16}, year={1995}, month={Aug}, pages={2127-30}, abstract={ Large quasi-electrostatic (QE) fields above thunderclouds produce an upward traveling beam of approximately 1 MeV runaway electrons which may contribute to the production of optical emissions above thunderclouds referred to as red sprites. Results of a one dimensional computer simulation model suggest that the runaway electrons can produce optical emissions similar in intensity and spectra to those observed in red sprites, but only for large QE fields produced by positive cloud-to-ground discharges lowering 250 C or more to ground from an altitude of at least 10 km. Differences in predicted optical spectra from that of other mechanisms suggest that the runaway electron mechanism can be readily tested by high resolution spectral measurements of red sprites }, keywords={ atmospheric electricity electric fields electron beam effects mesosphere thunderstorms source red sprites mesosphere quasielectrostatic fields thunderclouds upward travelling electron beam optical emissions 1D computer simulation model emission intensity upward discharges positive cloud-to-ground discharges predicted optical spectra runaway electron mechanism 20 keV to 20 MeV }, mynotes={UNREAD}, } @ARTICLE{SonwalkarMay95, author={Sonwalkar, V.S. and Inan, U.S. and Aggson, T.L. and Farrell, W.M. and Pfaff, R.}, title={ Focusing of nonducted whistlers by the equatorial anomaly }, journal={Journal of Geophysical Research}, volume={100}, number={A5}, year={1995}, month={May}, pages={7783-90}, abstract={ Impulsive ELF/VLF electric field bursts observed by the vector electric field instrument (VEFI) on the Dynamics Explorer 2 (DE 2) satellite on almost every crossing of the geomagnetic equator in the evening hours are interpreted as originating in lightning discharges. These signals that peak in intensity near the magnetic equator are observed within 5-20 degrees latitude of the geomagnetic equator at altitudes of 300-500 km with amplitudes of the order of approximately mV/m in the 512- to 1024-Hz frequency band of the VEFI instrument. Whistler-mode ELF/VLF wave propagation through a horizontally stratified ionosphere predicts strong attenuation of subionospheric signals reaching the equator at low altitudes. However, ray tracing analysis shows that the presence of the equatorial density anomaly, commonly observed in the upper ionosphere during evening hours, leads to the focusing of the wave energy from lightning near the geomagnetic equator at low altitudes, thus accounting for all observed aspects of the phenomenon. The observations presented indicate that during certain hours in the evening, almost all the energy input from lightning discharges entering the ionosphere at <30 degrees latitude remains confined to a small region (in altitude and latitude) near the geomagnetic equator. The net wideband electric field, extrapolated from the observed electric field values in the 512- to 1024-Hz band, can be approximately 10 mV/m or higher. These strong electric fields generated in the ionosphere by lightning at local evening times may be important for the equatorial electrodynamics of the ionosphere }, keywords={ F-region ionospheric electromagnetic wave propagation whistlers radiowave propagation nonducted whistlers whistler focusing ionosphere equatorial electrodynamics equatorial anomaly impulsive ELF electric field burst VLF lightning F-region horizontally stratified ionosphere strong attenuation 300 to 500 km }, mynotes={UNREAD}, } @ARTICLE{PaskoFeb95, author={Pasko, V.P. and Inan, U.S. and Taranenko, Y.N. and Bell, T.F.}, title={ Heating, ionization and upward discharges in the mesosphere due to intense quasi-electrostatic thundercloud fields }, journal={Geophysical Research Letters}, volume={22}, number={4}, year={1995}, month={Feb}, pages={365-8}, abstract={ Quasi-electrostatic fields that temporarily exist at high altitudes following the sudden removal (e.g. by a lightning discharge) of thundercloud charge at low altitudes are found to significantly heat mesospheric electrons and produce ionization and light. The intensity, spatial extent, duration and spectra of optical emissions produced are consistent with the observed features of the red sprite type of upward discharges }, keywords={ atmospheric ionisation electrons electrostatic discharge mesosphere plasma heating thunderstorms mesospheric electron heating ionization upward discharges mesosphere intense quasielectrostatic thundercloud fields lightning discharge sudden thundercloud charge removal light production ionization production intensity spatial extent duration spectra optical emissions red sprites }, mynotes={UNREAD}, } @ARTICLE{SonwalkarFeb95, author={Sonwalkar, V.S. and Inan, U.S. and Bell, T.F.}, title={ An interpretation of a mysterious 3.0- to 4.6-kHz emission band observed on Voyager 2 near Neptune }, journal={Journal of Geophysical Research}, volume={100}, number={A2}, year={1995}, month={Feb}, pages={1795-809}, abstract={ A whistler mode interpretation is provided for the narrowband signal (f approximately 3-4.6 kHz, Delta f approximately 200-800 Hz) detected by the plasma wave instrument on Voyager 2 during its encounter with Neptune. The analysis indicates that this signal may have been generated in a limited spatial region and that it propagated to other regions of the Neptunian magnetosphere in the nonducted whistler mode with wave normal vectors lying close to the whistler mode resonance cone. The observed frequency variation of the emission along the Voyager 2 trajectory is consistent with this interpretation. The source location is estimated to be near the magnetic equator at L approximately 4 and dipole longitude of 111 degrees W (260 degrees W longitude in Neptune coordinate system). The source frequency and bandwidth are estimated to be 3.6 kHz and 300 Hz, respectively. The waves most likely would have been generated by energetic electrons with 2- to 20-keV parallel energy via a gyroresonance mechanism. The interpretation of the narrowband emissions places the following limits on the Neptunian thermal plasma density and temperature: (1) N/sub e,min/>0.16 el/cm/sup 3/ for 1.2R/sub N/770 km distance between NAA and the NAU-Gander great circle path. Heating by the NSS (21.4 kHz, 265 kW) and NLK (24.8 kHz, 850 kW) transmitters was observed serendipitously in data from earlier measurements of the amplitudes of VLF signals propagating in the Earth-ionosphere waveguide. A three-dimensional model of wave absorption and electron heating in a magnetized, weakly ionized plasma is used to calculate the extent and shape of the collision frequency (i.e. electron temperature) enhancement above a VLF transmitter. The calculated changes in the D-region conductivity are used in a three-dimensional model of propagation in the Earth-ionosphere waveguide to predict the effect of the heated patch on a subionospheric VLF probe wave }, keywords={ D-region Earth-ionosphere waveguide ionospheric disturbances plasma radiofrequency heating radiowave propagation heated nighttime D-region Earth-ionosphere waveguide VLF signals ionospheric cooling ionospheric heating NAA transmitter NSS probe wave NAU probe wave NSS transmitter NLK transmitter 3D propagation model wave absorption electron heating magnetized weakly ionized plasma collision frequency electron temperature enhancement D-region conductivity subionospheric VLF probe wave 24 kHz 21.4 kHz 28.5 kHz 24.8 kHz }, mynotes={UNREAD}, } @ARTICLE{BellApr94, author={Bell, T.F. and Inan, U.S. and Lauben, D. and Sonwalkar, V.S. and Helliwell, R.A. and Sobolev, Ya.P. and Chmyrev, V.M. and Gonzalez, S.}, title={ DE-1 and COSMOS 1809 observations of lower hybrid waves excited by VLF whistler mode waves }, journal={Geophysical Research Letters}, volume={21}, number={8}, year={1994}, month={Apr}, pages={653-6}, abstract={ Past work demonstrates that strong lower hybrid (LH) waves can be excited by electromagnetic whistler mode waves throughout large regions of the topside ionosphere and magnetosphere. The effects of the excited LH waves upon the suprathermal ion population in the topside ionosphere and magnetosphere depend upon the distribution of LH wave amplitude with wavelength lambda . The present work reports plasma wave data from the DE-1 and COSMOS 1809 spacecraft which suggests that the excited LH wave spectrum has components for which lambda or=6 eV energy range can be heated by 20 to 40 eV as a result of a single lightning discharge. They also show how the number density of >or=6 eV H/sup +/ ions is enhanced by preheating resulting from the absorption of proton whistlers in the 500-1000 km altitude range. For lightning discharge rates of one or more per second over a 10/sup 4/ km/sup 2/ area, the authors' model predicts a total energy gain for the H/sup +/ ions of 400 eV to 2 KeV and a perpendicular ion flux of j/sub perpendicular to / approximately 10/sup 5/ to 10/sup 6/ cm/sup -2/ sec/sup -1/. These fluxes should be observable on low altitude spacecraft using presently available instrumentation }, keywords={ ionosphere ionospheric electromagnetic wave propagation thunderstorms whistlers ion heating lower atmosphere meteorology plasma wave radiowave suprathermal ions thunderstorm cells topside ionosphere lower hybrid waves linear mode coupling intense electromagnetic whistler mode radiation lightning field-aligned plasma density irregularities H/sup +/ whistlers 500 to 1000 km H }, mynotes={UNREAD}, } @ARTICLE{TaranenkoAug93, author={Taranenko, Y.N. and Inan, U.S. and Bell, T.F.}, title={ Interaction with the lower ionosphere of electromagnetic pulses from lightning: heating, attachment, and ionization }, journal={Geophysical Research Letters}, volume={20}, number={15}, year={1993}, month={Aug}, pages={1539-42}, abstract={ A Boltzmann formulation of the electron distribution function and Maxwell's equations for the electromagnetic (EM) fields are used to simulate the interaction of lightning radiated EM pulses with the lower ionosphere. Ionization and dissociative attachment induced by the heated electrons cause significant changes in the local electron density (N/sub e/). Due to 'slow' field changes of typical lightning EM pulses over time scales of tens of mu s, the distribution function follows the quasi-equilibrium solution of the Boltzmann equation in the altitude range of interest (70 to 100 km). The EM pulse is simulated as a planar 100 mu s-long single period oscillation of a 10-kHz wave injected at 70 km. Under nighttime conditions, individual pulses of intensity 10-20 V/m (normalized to 100 km horizontal distance) produce changes in N/sub e/ of 1-30% while a sequence of pulses leads to strong modification of N/sub e/ at altitudes <95 km. The N/sub e/ changes produce a 'sharpening' of the lower ionospheric boundary by causing a reduction in electron density at 75-85 km (due to attachment) and a substantial increase at 85-95 km (due to ionization) (e.g. the scale height decreases by a factor of approximately 2 at approximately 85 km for a single 20 V/m EM pulse). No substantial N/sub e/ changes occur during daytime }, keywords={ atmospheric ionisation electromagnetic pulse electron attachment ionospheric electromagnetic wave propagation lightning plasma heating lower ionosphere lightning radiated EM pulses heating VLF perturbations ionization Boltzmann equation Maxwell equations dissociative attachment heated electrons local electron density oscillation nighttime conditions modification 70 to 100 km 100 mus 10 kHz }, mynotes={UNREAD}, } @ARTICLE{PoulsenSep93, author={Poulsen, W.L. and Bell, T.F. and Inan, U.S.}, title={ The scattering of VLF waves by localized ionospheric disturbances produced by lightning-induced electron precipitation }, journal={Journal of Geophysical Research}, volume={98}, number={A9}, year={1993}, month={Sep}, pages={15553-9}, abstract={ A 3D model of the scattering of VLF waves in the Earth-ionosphere waveguide by localized disturbances in the lower ionosphere is examined for typical disturbances expected to be produced by lightning-induced electron precipitation events. Results indicate that the scattering is generally independent of the conductivity and permittivity of the Earth's surface immediately beneath the disturbed region except for extremely low conductivities such as that found over deep ice caps. Thus the scattered signal is principally a function of the ionospheric perturbation. For typical disturbances characterized by altitude profiles of enhanced ionization expected for 1.4or=5.0. ELF/VLF noise measured near the epicenters was analyzed for occurrence rates and average spectra, as well as for peak and mean electric field intensities in three spectrometers covering a frequency range of 4 Hz-512 kHz in 20 channels }, keywords={ atmospheric radiation earthquakes ionosphere ionospheric electromagnetic wave propagation magnetosphere terrestrial electricity ELF VLF radiowave emission earthquake induced EM wave geoelectric precursor AD 1983 magnetosphere AD 1981 AD 1982 ionosphere DE 2 0.3 to 512 kHz 4 to 300 Hz }, mynotes={UNREAD}, } @ARTICLE{PoulsenFeb93, author={Poulsen, W.L. and Inan, U.S. and Bell, T.F.}, title={ A multiple-mode three-dimensional model of VLF propagation in the Earth-ionosphere waveguide in the presence of localized D region disturbances }, journal={Journal of Geophysical Research}, volume={98}, number={A2}, year={1993}, month={Feb}, pages={1705-17}, abstract={ Transient localized D region disturbances, such as those associated with lightning discharges, affect the characteristics of VLF waves propagating in the Earth-ionosphere waveguide. In particular, both phase and amplitude changes in the subionospheric signal can be observed at receiving sites as a result of the wave scattering that takes place in the disturbed region. The authors present a multiple-mode three-dimensional model of VLF propagation in the Earth-ionosphere waveguide in the presence of localized D region disturbances. This new model is applied to experimental observations and is found to be in general agreement. The diagnostics potential of the model for characterizing energetic particle precipitation events is discussed }, keywords={ atmospheric elementary particle precipitation D-region ionospheric electromagnetic wave propagation radiowave propagation D-region radiowave propagation multiple-mode three-dimensional model VLF propagation Earth-ionosphere waveguide VLF waves phase amplitude subionospheric signal energetic particle precipitation events }, mynotes={UNREAD}, } @ARTICLE{InanOct92, author={Inan, U.S. and Rodriguez, J.V. and Lev-Tov, S. and Oh, J.}, title={ Ionospheric modification with a VLF transmitter }, journal={Geophysical Research Letters}, volume={19}, number={20}, year={1992}, month={Oct}, pages={2071-4}, abstract={ Detectable heating of the nighttime D-region by a 28.5 kHz signal is observed in 16 out of 144 cases with events occurring under conditions of moderate to low D-region electron densities as represented by the unperturbed VLF signal levels. Three dimensional modeling of the effects of NAU heating on a probe VLF signal predicts values in general agreement with observations and suggests that maximum effects should occur under tenuous D-region conditions }, keywords={ D-region ionospheric electromagnetic wave propagation plasma radiofrequency heating night radiowave heating D-region ionosphere modification three-dimensional model AD 1989 VLF transmitter nighttime modeling 28.5 kHz }, mynotes={UNREAD}, } @ARTICLE{RodriguezOct92, author={Rodriguez, J.V. and Inan, U.S. and Bell, T.F.}, title={ D region disturbances caused by electromagnetic pulses from lightning }, journal={Geophysical Research Letters}, volume={19}, number={20}, year={1992}, month={Oct}, pages={2067-70}, abstract={ Electromagnetic pulses from weak lightning discharges (E/sub 100/=1 V/m, where E/sub 100/ is the field strength in the radiation pattern maximum at 100 km) may substantially heat D region electrons, while only pulses with E/sub 100/>or=20 V/m may create electron density enhancements >or=10% of ambient. A E/sub 100/=20 V/m pulse from a horizontal radiator at 5 km altitude (e.g. the cloud discharge at the stepped-leader onset) increases the electron temperature by a factor of approximately 400 maximum and the electron density (in one ionization cycle) by approximately 230 cm/sup 3/ maximum; the widths at half-maximum of the heated and ionized regions are 200 km and 90 km. A E/sub 100/=40 V/m pulse from a vertical radiator at 0 km altitude (e.g. the vertical return stroke channel) increases the electron temperature by a factor of approximately 350 maximum and the electron density by approximately 80 cm/sup 3/ maximum }, keywords={ D-region lightning electron heating modification EM pulse EM radiation disturbance radiowave emission D-region ionosphere electromagnetic pulses lightning electron temperature }, mynotes={UNREAD}, } @ARTICLE{TaranenkoSep92, author={Taranenko, Y.N. and Inan, U.S. and Bell, T.F.}, title={ Optical signatures of lightning-induced heating of the D region }, journal={Geophysical Research Letters}, volume={19}, number={18}, year={1992}, month={Sep}, pages={1815-18}, abstract={ Lightning-induced heating of the nighttime D region leads to the excitation of a number of lines of O, O/sub 2/, N/sub 2/, O/sub 2//sup +/, and N/sub 2//sup +/, at intensities of 10-10/sup 9/ rayleighs (R) for vertical observations. For example, the 5577 AA emission from O has intensity approximately 60 R lasting for approximately 350 ms while the 1st and 2nd positive bands of N/sub 2/ are at approximately 10/sup 9/ R but last only approximately 50 mu s }, keywords={ airglow D-region lightning plasma heating visible D-region ionosphere airglow lightning-induced heating O O/sub 2/ N/sub 2/ O/sub 2//sup +/ N/sub 2//sup +/ }, mynotes={UNREAD}, } @ARTICLE{GlukhovNov92, author={Glukhov, V.S. and Pasko, V.P. and Inan, U.S.}, title={ Relaxation of transient lower ionospheric disturbances caused by lightning-whistler-induced electron precipitation bursts }, journal={Journal of Geophysical Research}, volume={97}, number={A11}, year={1992}, month={Nov}, pages={16971-9}, abstract={ A quantitative model of the relaxation of transient lower ionospheric (D-region) disturbances caused by lightning-induced electron precipitation is developed, taking advantage of known particular features of the lightning-induced disturbances, such as the fact that they are produced in typically <1 s and decay over 10-100 s. The model represents the nighttime D-region as consisting of only four kinds of charged particles (electrons, positive ions, negative ions, and positive cluster ions) and is particularly suited for description of the detailed behavior of the electron density. Application of the model to some previously modeled disturbances indicates that some of the least known chemical reaction rates in the nighttime D-region altitudes may be measurable using subionospheric VLF data }, keywords={ atmospheric electron precipitation D-region ionosphere lightning D-region transient lower ionospheric disturbances lightning-whistler-induced electron precipitation bursts quantitative model relaxation }, mynotes={UNREAD}, } @ARTICLE{JasnaAug92, author={Jasna, D. and Inan, U.S. and Bell, T.F.}, title={ Precipitation of suprathermal (100 eV) electrons by oblique whistler waves }, journal={Geophysical Research Letters}, volume={19}, number={16}, year={1992}, month={Aug}, pages={1639-42}, abstract={ Electron precipitation induced by oblique whistler waves is investigated using a new test particle simulation code based on gyro-averaged equations of motion. The results indicate that highly oblique waves can efficiently pitch angle scatter suprathermal electrons (10-100 eV). At L=3, for example, in a single encounter with a wave with power density S approximately 8 pW/m/sup 2/ propagating at psi =60 degrees with respect to the Earth's magnetic field B/sub 0/, the average pitch angle scattering of 100 eV electrons is approximately 0.1 degrees . In comparison, the average scattering of energetic (100 keV) electrons by a parallel propagating wave with the same S is approximately 0.01 degrees . Estimates indicate that the precipitated electron energy fluxes resulting from the interaction of approximately 100 eV electrons with oblique waves can be up to 30 times larger than that due to the precipitation of 100 keV electrons by parallel propagating waves }, keywords={ atmospheric electron precipitation magnetosphere magnetospheric electromagnetic wave propagation plasma radiation belts whistlers radiation belt electrons VLF magnetosphere suprathermal electrons precipitation wave-particle interactions wave propagation direction whistler wave power density oblique whistler waves test particle simulation code gyro-averaged equations of motion highly oblique waves average pitch angle scattering precipitated electron energy fluxes 100 eV 10 to 25 kHz 5.60 to 15.79 kHz }, mynotes={UNREAD}, } @ARTICLE{ImhofSep92, author={Imhof, W.L. and Voss, H.D. and Mobilia, J. and Datlowe, D.W. and Gaines, E.E. and McGlennon, J.P. and Inan, U.S.}, title={ Relativistic electron microbursts }, journal={Journal of Geophysical Research}, volume={97}, number={A9}, year={1992}, month={Sep}, pages={13829-37}, abstract={ The authors report the first satellite observations of relativistic (>1 MeV) electron precipitation in microbursts with measured durations of less than 1 s. The data on these relativistic microbursts appear to indicate that many of the bursts may be due to wave-particle interaction not with whistler mode chorus but possibly with other waveforms. The locations of many of the relativistic microbursts are concentrated at the outer edge of the trapped radiation belt, where the gyroradii of the electrons are comparable to the curvature of the magnetic field lines and stable trapping may therefore not occur. The preferred location of the microbursts, which may be primarily spatial in character, implies the possible importance of irregularities in the magnetic field lines near the trapping boundary as the responsible mechanism }, keywords={ atmospheric electron precipitation radiation belts magnetosphere atmosphere electron microbursts relativistic microbursts wave-particle interaction trapped radiation belt gyroradii 1 MeV }, mynotes={UNREAD}, } @ARTICLE{InanApr92, author={Inan, U.S. and Chiu, Y.T. and Davidson, G.T.}, title={ Whistler-mode chorus and morningside aurorae }, journal={Geophysical Research Letters}, volume={19}, number={7}, year={1992}, month={Apr}, pages={653-6}, abstract={ Quasi-electrostatic ELF/VLF chorus emissions immediately above the equatorial half-gyrofrequency, observed to propagate with wave normal angle ( psi ) within 0.4-1.2 degrees of the resonance cone ( psi /sub r/) (Muto et al., 1987), are shown to efficiently resonate with 0.1-10 keV electrons. These waves may thus be important in driving the relatively low energy (<10 keV) component of pulsating aurorae and the morning-side diffuse aurorae ( approximately 1 keV) }, keywords={ atmospheric electron precipitation aurora magnetospheric electromagnetic wave propagation radiowave propagation whistlers whistler mode chorus electron precipitation quasielectrostatic ELF-VLF chorus emission radiowaves magnetosphere morningside aurorae pulsating aurorae diffuse aurorae 0.1 to 10 keV }, mynotes={UNREAD}, } @ARTICLE{DraganovFeb92, author={Draganov, A.B. and Inan, U.S. and Sonwalkar, V.S. and Bell, T.F.}, title={ Magnetospherically reflected whistlers as a source of plasmaspheric hiss }, journal={Geophysical Research Letters}, volume={19}, number={3}, year={1992}, month={Feb}, pages={233-6}, abstract={ Ray-tracing simulations and estimates of whistler wave damping show that magnetospherically reflected whistlers can persist for approximately 10/sup 2/ s in a low frequency band (f approximately 1 kHz). The combined contribution from whistler rays produced by a single lightning flash but entering the magnetosphere at different points form a continuous hiss-like signal, as observed at a fixed point. Estimates indicate that the total whistler wave energy input into the magnetosphere from lightning discharges may maintain experimentally observed levels of magnetospheric hiss }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation whistlers magnetosphere plasmasphere radiowave emission ELF whistler reflection reflected whistlers hiss whistler wave damping lightning magnetosphere 1 kHz }, mynotes={UNREAD}, } @ARTICLE{TaranenkoJan92, author={Taranenko, Y.N. and Inan, U.S. and Bell, T.F.}, title={ VLF-HF heating of the lower ionosphere and ELF wave generation }, journal={Geophysical Research Letters}, volume={19}, number={1}, year={1992}, month={Jan}, pages={61-4}, abstract={ For incident wave power densities of 10/sup -6/-10/sup -2/ W/m/sup 2/ (at 30 km altitude), VLF heating of the D-region (<90 km) is found to be 2-10 times more effective (depending on power) than HF heating, resulting in comparable perturbations of subionospheric VLF probe waves in spite of up to 10/sup 3/ times larger power density utilized in HF heating and at least as efficient in ELF wave generation. In view of generally larger (100*100 km) areas of the ionosphere illuminated by VLF transmitters, ELF wave generation by modulated VLF heating is estimated to produce ELF power levels of approximately 100 mW, comparable with or larger than those produced in typical HF heating experiments. ELF wave generation in a typical midlatitude ambient ionosphere occurs primarily via the modulation of Pedersen current whereas in a typical auroral ionosphere Hall current is dominant for pump wave frequencies up to approximately 6 MHz. For 10-30 MHz and power densities >10/sup -4/ W/m/sup 2/, Pedersen current modulation is again dominant, potentially providing up to 2-15 times higher ELF dipole moment than those found in experiments using 3-5 MHz heaters }, keywords={ ionospheric electromagnetic wave propagation plasma radiofrequency heating radiowave propagation radiowave absorption lower ionosphere ELF wave generation power densities VLF heating D-region HF heating perturbations heating experiments Pedersen current auroral ionosphere Hall current pump wave frequencies modulation dipole moment 30 to 150 km }, mynotes={UNREAD}, } @ARTICLE{RodriguezJan92, author={Rodriguez, J.V. and Inan, U.S. and Li, Y.Q. and Holzworth, R.H. and Smith, A.J. and Orville, R.E. and Rosenberg, T.J.}, title={ A case study of lightning, whistlers, and associated ionospheric effects during a substorm particle injection event }, journal={Journal of Geophysical Research}, volume={97}, number={A1}, year={1992}, month={Jan}, pages={65-75}, abstract={ Simultaneous ground-based observations of narrowband and broadband VLF radio waves and of cloud-to-ground lightning were made at widely spaced locations during the 1987 Wave-Induced Particle Precipitation (WIPP) campaign, conducted from Wallops Island, Virginia. Based on these observations, the first case study has been made of the relationships among located cloud-to-ground (CG) lightning flashes, whistlers, and associated ionospheric effects during a substorm particle injection event. This event took place two days after the strongest geomagnetic storm of 1987, during a reintensification in geomagnetic activity (Kp=5) that did not affect the high rate of whistlers observed at Faraday Station, Antarctica (L=2.46). At the time of the injection event, several intense nighttime thunderstorms were located over Long Island and the coast of New England, between 400 km northwest and 600 km north of the region geomagnetically conjugate to Faraday }, keywords={ atmospherics lightning magnetic storms whistlers cloud to ground flashes atmospherics United States lightning whistlers ionospheric effects substorm particle injection event VLF radio waves geomagnetic storm geomagnetic activity intense nighttime thunderstorms Long Island New England }, mynotes={UNREAD}, } @ARTICLE{InanApr91, author={Inan, U.S. and Bell, T.F. and Rodriguez, J.V.}, title={ Heating and ionization of the lower ionosphere by lightning }, journal={Geophysical Research Letters}, volume={18}, number={4}, year={1991}, month={Apr}, pages={705-8}, abstract={ Nighttime ionospheric electrons at 90-95 km altitude are heated by a factor of 100-500 during the upward passage of short (<100 mu s) pulses of intense (5-20 V/m at 100 km distance) electromagnetic radiation from lightning. Heated electrons with average energy of 4-20 eV in turn produce secondary ionization, of up to 400 cm/sup -3/ at approximately 95 km altitude in a single ionization cycle ( approximately 3 mu s). With the time constant of heating being 5-10 mu s, a number of such ionization cycles can occur during a 50 mu s radiation pulse, leading to even higher density enhancements. This effect can account for observations of 'early' or 'fast' subionospheric VLF perturbations }, keywords={ atmospheric ionisation atmospheric radiation atmospheric temperature atmospheric thermodynamics D-region electron density ionosphere ionospheric electromagnetic wave propagation lightning nighttime ionospheric electrons heating aeronomy short intense EM radiation pulses ionosphere ionisation D-region ionisation hot electrons energy ionisation cycle time EM pulse duration ionosphere heating time constant fast VLF perturbations ionisation bubbles lower ionosphere lightning secondary ionization single ionization cycle density enhancements subionospheric VLF perturbations 90 to 95 km 3000 ns 100 km 5 to 10 mus 50 mus 4 to 20 eV }, mynotes={UNREAD}, } @ARTICLE{DraganovJun91, author={Draganov, A.B. and Inan, U.S. and Taranenko, Y.N.}, title={ ULF magnetic signatures at the Earth surface due to ground water flow: a possible precursor to earthquakes }, journal={Geophysical Research Letters}, volume={18}, number={6}, year={1991}, month={Jun}, pages={1127-30}, abstract={ Magnetic field fluctuations at the Earth's surface of Delta B/B approximately 10/sup -5/ at <1 Hz are shown to result from motion with a peak velocity of approximately 4 cm/s of ground water ( approximately 4 S/m) at approximately 5 km depth. Surface field changes can occur due to either divergence free fluid motion with transverse spatial wavelengths of a few tens of km, and/or homogeneous flow which displaces local inhomogeneities in the Earth magnetic field }, keywords={ earthquakes groundwater seismology terrestrial electricity earthquake seismology groundwater magnetic field fluctuation ULF magnetic signatures Earth surface ground water flow precursor divergence free fluid motion 0.01 to 0.5 Hz }, mynotes={UNREAD}, } @ARTICLE{BellMar91, author={Bell, T.F. and Inan, U.S. and Sonwalkar, V.S. and Helliwell, R.A.}, title={ DE-1 observations of lower hybrid waves excited by VLF whistler mode waves }, journal={Geophysical Research Letters}, volume={18}, number={3}, year={1991}, month={Mar}, pages={393-6}, abstract={ Recent satellite data show high amplitude lower hybrid (LH) waves excited by electromagnetic (EM) whistler mode waves throughout magnetospheric regions where small scale magnetic-field-aligned plasma density irregularities exist. One important consequence in the auroral acceleration region is the heating of suprathermal ions by the excited LH waves. To evaluate such heating it is necessary to know the wavelength ( lambda ) range of the waves, information not previously available since most past observations were made with long (l>or=75; l=antenna length) electric dipole antennas which have very poor response for lambda 40 keV electrons in association with ducted whistlers may thus be accompanied by substantial fluxes of lower energy (10 eV-40 keV) electrons precipitated by the nonducted components }, keywords={ atmospheric electron precipitation magnetosphere radiation belts EM wave radiowave electron precipitation radiation belt loss process magnetosphere wave particle interaction first order cyclotron energetic particles oblique whistler waves Landau resonant pitch angle scattering }, mynotes={UNREAD}, } @ARTICLE{WolfDec90, author={Wolf, T.G. and Inan, U.S.}, title={ Path-dependent properties of subionospheric VLF amplitude and phase perturbations associated with lightning }, journal={Journal of Geophysical Research}, volume={95}, number={A12}, year={1990}, month={Dec}, pages={20997-10015}, abstract={ A comprehensive study of lightning-associated amplitude and phase perturbations on multiple VLF/LF signals (Trimpi events) observed at Stanford, California and at Palmer Station, Antarctica, has revealed a number of new properties that appear to be characteristic of the particular signal paths. None of the existing models of the Trimpi effect are found to explain all of the observed new features. Instead, the new experimental findings provide an empirical framework to guide the evaluation of more sophisticated models }, keywords={ ionospheric electromagnetic wave propagation lightning radiowave propagation subionospheric amplitude perturbations phase perturbations lightning multiple VLF/LF signals Trimpi events }, mynotes={UNREAD}, } @ARTICLE{JasnaOct90, author={Jasna, D. and Inan, U.S. and Bell, T.F.}, title={ Equatorial gyroresonance between electrons and magnetospherically reflected whistlers }, journal={Geophysical Research Letters}, volume={17}, number={11}, year={1990}, month={Oct}, pages={1865-8}, abstract={ Magnetospherically reflected whistlers resonantly interact with energetic (of order 100 keV) electrons in a relatively narrow energy range during multiple equatorial crossings over a wide range of L-shells (1.54 over a approximately 40 degrees range of latitudes including the geomagnetic equator and are often accompanied by discrete emissions or a band of hiss. Some observed features are consistent with previous observations of electrostatic plasma waves (Ondoh et al., 1989; Reinleitner et al., 1983); however, the magnetic measurements clearly indicate that the impulsive signals are electromagnetic in nature. The possibility of spacecraft discharge effects as the cause of these signals is discussed }, keywords={ artificial satellites atmospheric radiation magnetosphere AD 1985 01 to 1989 12 magnetosphere wideband VLF EM bursts Dynamics Explorer 1 DE 1 satellite discrete emissions hiss impulsive signals spacecraft discharge effects 0.650 to 16.0 kHz }, mynotes={UNREAD}, } @ARTICLE{InanOct90, author={Inan, U.S. and Knifsend, F.A. and Oh, J.}, title={ Subionospheric VLF 'imaging' of lightening-induced electron precipitation from the magnetosphere }, journal={Journal of Geophysical Research}, volume={95}, number={A10}, year={1990}, month={Oct}, pages={17217-31}, abstract={ High-resolution measurements of subionospheric VLF signals at multiple sites are used as a new tool to assess the spatial distribution and occurrence of ionospheric disturbances associated with lightning-induced electron precipitation. Simultaneous observations in California, Saskatchewan and Quebec of VLF signals from multiple sources allow the monitoring of event activity over a coarse grid covering the continental United States. Association of the observed VLF signal perturbations with lightning is often made on the basis of time correlation with prominent radio atmospherics. Simultaneous observations of individual events on subionospheric paths that 'cross' one another are used to locate the disturbed ionospheric region(s). Absence of perturbations on nearby paths permits assessment of the spatial extent of the region with a varying degree of accuracy, depending on the distribution of signal paths }, keywords={ atmospheric electron precipitation ionosphere magnetosphere subionospheric imaging lightening-induced electron precipitation magnetosphere spatial distribution occurrence ionospheric disturbances California Saskatchewan Quebec United States }, mynotes={UNREAD}, } @ARTICLE{GailSep90, author={Gail, W.B. and Inan, U.S. and Helliwell, R.A. and Carpenter, D.L.}, title={ Gyroresonant wave-particle interactions in a dynamic magnetosphere }, journal={Journal of Geophysical Research}, volume={95}, number={A9}, year={1990}, month={Sep}, pages={15103-12}, abstract={ Experimental and theoretical methods for studying gyroresonant wave-particle interactions (WPI) in the magnetosphere commonly assume that the magnetic field is static over the time scales of interest. In order to investigate the effect of nonequilibrium or dynamic magnetospheric processes in WPI, the response of the interaction mechanism to time-dependent perturbations in the magnetic field was examined using the global field compressions that occur during sudden commencements (sc). By measuring modifications of the wave spectrum and electron distribution during sc, the response of the WPI mechanism to slow variations in the magnetic field and plasma environment can be determined. This technique was used to examine the applicability of both nonlinear and quasi-linear descriptions of gyroresonant WPI to dynamic environments }, keywords={ magnetosphere plasma nonequilibrium processes atmosphere dynamic magnetosphere gyroresonant wave-particle interactions magnetic field time-dependent perturbations global field compressions sudden commencements wave spectrum electron distribution plasma quasi-linear descriptions }, mynotes={UNREAD}, } @ARTICLE{CarlsonSep90, author={Carlson, C.R. and Helliwell, R.A. and Inan, U.S.}, title={ Space-time evolution of whistler mode wave growth in the magnetosphere }, journal={Journal of Geophysical Research}, volume={95}, number={A9}, year={1990}, month={Sep}, pages={15073-89}, abstract={ A new model is developed to simulate the space-time evolution of a propagating coherent whistler mode wave pulse in the magnetosphere. The model is applied to the case of single frequency (2-6 kHz) wave pulses injected into the magnetosphere near L approximately=4, using the VLF transmitting facility at Siple Station, Antarctica. The mechanism for growth is cyclotron resonance between the circularly polarized waves and the gyrating energetic electrons of the radiation belts }, keywords={ magnetospheric electromagnetic wave propagation radiowave propagation whistlers whistler mode wave growth magnetosphere space-time evolution VLF cyclotron resonance radiation belts 2 to 6 kHz }, mynotes={UNREAD}, } @ARTICLE{JamesAug90, author={James, H.G. and Inan, U.S. and Rietveld, M.T.}, title={ Observations on the DE 1 spacecraft of ELF/VLF waves generated by an ionospheric heater }, journal={Journal of Geophysical Research}, volume={95}, number={A8}, year={1990}, month={Aug}, pages={12187-95}, abstract={ Radio waves at frequencies between 1525 and 5925 Hz were observed on the DE 1 satellite during a pass over the Heating facility of the Max-Planck-Institut fur Aeronomie (MPAe Heating) near Tromso, Norway. The waves were detected during a 2-min period on December 12, 1981, and measurements indicated pulse stretching by a few hundred milliseconds and spectral broadening of about 10 Hz. Measured signal delays are compared with those calculated using three-dimensional ray tracing. Scattering by density irregularities may be responsible for the observed long delays and spectral broadening }, keywords={ ionospheric electromagnetic wave propagation plasma radiofrequency heating radiowave propagation radiowave heating AD 1981 12 12 MF ELF/VLF waves ionospheric heater DE 1 satellite MPAe Heating pulse stretching spectral broadening signal delays density irregularities 1525 Hz 5925 Hz 2.759 MHz }, mynotes={UNREAD}, } @ARTICLE{RosenbergMay90, author={Rosenberg, T.J. and Wei, R. and Detrick, D.L. and Inan, U.S.}, title={ Observations and modeling of wave-induced microburst electron precipitation }, journal={Journal of Geophysical Research}, volume={95}, number={A5}, year={1990}, month={May}, pages={6467-75}, abstract={ Energy-time features of X-ray microbursts are examined and compared with the predictions of a test particle simulation model of wave-induced electron precipitation resulting from gyroresonant wave-particle interactions in the magnetosphere. The observations were obtained on a balloon flight at Siple station, Antarctica (L approximately=4.2) on December 30, 1980. The energy and time evolution of the microbursts were studied for X-rays in the energy range from 25 to 175 keV. The authors identify the narrow microbursts with electrons which are precipitated directly after undergoing pitch-angle scattering interactions with the wave pulse; the wide microbursts are identified with electrons which, after interacting with the wave, mirror in the conjugate ionosphere before precipitating into the southern ionosphere. In general, the results provide further support for the gyroresonant test particle simulation model, and for the belief that the observed type of microbursts originates in the vicinity of the magnetic equator in a gyroresonant process involving discrete chorus emissions }, keywords={ atmospheric electron precipitation atmospheric radiation magnetosphere radiation belts AD 1980 12 30 ionosphere radiation belt wave-induced microburst electron precipitation X-ray microbursts test particle simulation model gyroresonant wave-particle interactions magnetosphere pitch-angle scattering interactions 25 to 175 keV }, mynotes={UNREAD}, } @ARTICLE{InanMay90, title={ VLF heating of the lower ionosphere }, journal={Geophysical Research Letters}, volume={17}, number={6}, year={1990}, month={May}, pages={729-32}, abstract={ A controlled wave-injection experiment with a 28.5 kHz transmitter having a radiated power of 100 kW has revealed evidence of ionospheric heating by the VLF waves. Calculations indicate that the observed effect can be attributed to the absorption of wave energy in the lower ionosphere, which is estimated to result in a 30% enhancement in the collision frequency at 85 km. This process also represents a new means of direct coupling of lightning energy to the lower ionosphere }, keywords={ atmospherics ionosphere lightning radiowave heating experiment atmospherics ionospheric modification VLF heating lower ionosphere wave-injection experiment absorption wave energy direct coupling lightning energy 28.5 kHz }, mynotes={UNREAD}, } @ARTICLE{HelliwellApr90, author={Helliwell, R.A. and Mielke, T. and Inan, U.S.}, title={ Rapid whistler-mode wave growth resulting from frequency-time curvature }, journal={Geophysical Research Letters}, volume={17}, number={5}, year={1990}, month={Apr}, pages={599-602}, abstract={ The rapid (<50 ms) temporal growth of ducted whistlers is simulated using controlled injection of VLF pulses from the Siple Station, Antarctica transmitter. The results show that, when the frequency-time function of the injected pulse has a positive slope and negative curvature, producing a kind of 'chirp' such that it approximates the f(t) shape of a lightning-generated whistler at frequencies above the 'nose' frequency, growth up to a saturation level (20-30 dB) commonly occurs within <50 ms as opposed to 200-300 ms that is required for monochromatic input signals. The phenomenon is explained in terms of second-order-resonance theory }, keywords={ whistlers whistlers EM wave rapid growth whistler-mode wave growth frequency-time curvature ducted whistlers controlled injection VLF pulses Siple Station injected pulse second-order-resonance theory }, mynotes={UNREAD}, } @ARTICLE{GailJan90, author={Gail, W.B. and Inan, U.S.}, title={ Characteristics of wave-particle interactions during sudden commencements. 2. Spacecraft observations }, journal={Journal of Geophysical Research}, volume={95}, number={A1}, year={1990}, month={Jan}, pages={139-47}, abstract={ For pt.I see ibid., vol.95, no.A1, p.110-37 (1990). Wave data from the DE 1 spacecraft for 50 sudden commencements were analyzed for amplitude and spectral modifications and correlated with data from ground-based observatories. Changes in wave activity were identified in 14 of the events studied. The changes, which were commonly observed at frequencies below the local electron gyrofrequency, exhibited a complex structure both in frequency and in time and varied considerably among events }, keywords={ magnetic storms magnetospheric electromagnetic wave propagation plasma radiowave propagation spacecraft observations magnetic storms magnetosphere plasma amplitude modification wave-particle interactions sudden commencements DE 1 spectral modifications wave activity 0.3 to 30 kHz }, mynotes={UNREAD}, } @ARTICLE{GailJan90, author={Gail, W.B. and Inan, U.S. and Helliwell, R.A. and Carpenter, D.L. and Krishnaswamy, S. and Rosenberg, T.J. and Lanzerotti, L.J.}, title={ Characteristics of wave-particle interactions during sudden commencements. 1. Ground-based observations }, journal={Journal of Geophysical Research}, volume={95}, number={A1}, year={1990}, month={Jan}, pages={119-37}, abstract={ ELF-VLF (0.3-30 kHz) wave data measured at ground-based observatories for 250 sudden commencements were analyzed for amplitude and spectral modifications and correlated with magnetic field and precipitating particle observations. Changes in ELF-VLF wave activity at high-latitude stations were observed in 50-60% of the events studied and for approximately 80% of the events when the observing station was on the dayside. Characteristic, well-defined modifications of both coherent and incoherent ELF-VLF wave emissions were observed }, keywords={ magnetic storms magnetospheric electromagnetic wave propagation plasma radiowave propagation ELF VLF ground based observation magnetosphere plasma magnetic storm amplitude modification wave-particle interactions sudden commencements spectral modifications magnetic field precipitating particle wave activity 0.3 to 30 kHz }, mynotes={UNREAD}, } @ARTICLE{BurgessMar90, author={Burgess, W.C. and Inan, U.S.}, title={ Simultaneous disturbance of conjugate ionospheric regions in association with individual lightning flashes }, journal={Geophysical Research Letters}, volume={17}, number={3}, year={1990}, month={Mar}, pages={259-62}, abstract={ Characteristic whistler-associated amplitude perturbations of subionospheric VLF or LF signals ('Trimpi events') observed within one second of each other at Palmer Station, Antarctica and at Arecibo, Puerto Rico suggest that ionospheric regions in both northern and southern hemispheres are disturbed together in association with individual lightning flashes. During a one hour period on March 21, 1989, the onsets of 44 out of 47 perturbations measured on a 21.4 kHz signal from Maryland to Arecibo occurred within 1 s of perturbation onsets measured on a 23.4 kHz signal from Hawaii to Palmer Station. Similar activity occurred before and after this period, and on the preceding and following days. The observations are consistent with the disturbance of geomagnetically conjugate ionospheric regions by multiple bounces between hemispheres of bursts of radiation belt electrons, scattered in pitch angle by whistlers in the magnetosphere. Analysis of patterns of perturbations with corresponding whistler and lightning information from this period suggests that there were at least two distinct ionospheric disturbances in each hemisphere }, keywords={ ionosphere whistlers ionosphere conjugate region Trimpi event AD 1989 03 21 disturbance lightning flashes whistler-associated amplitude perturbations VLF LF Palmer Station Antarctica Arecibo Puerto Rico magnetosphere }, mynotes={UNREAD}, } @ARTICLE{PoulsenMar90, author={Poulsen, W.L. and Bell, T.F. and Inan, U.S.}, title={ Three-dimensional modeling of subionospheric VLF propagation in the presence of localized D region perturbations associated with lightning }, journal={Journal of Geophysical Research}, volume={95}, number={A3}, year={1990}, month={Mar}, pages={2355-66}, abstract={ A theoretical model of single-mode, subionospheric VLF wave propagation in the presence of localized perturbations of the nighttime D region has been developed. Values for changes in the amplitude and phase of a received signal were obtained and compared with amplitude and phase measurements of a VLF signal received at Palmer Station, Antarctica, from the NPM transmitter (23.4 kHz) in Hawaii during energetic electron precipitation events. Positive phase and/or negative amplitude shifts in the received signal are produced by perturbations centered on the great circle (GC) path, whereas both positive and negative amplitude (or phase) shifts in a single-mode signal can be produced by perturbations lying in regions off the GC path. The magnitude of the signal scattered by the perturbation towards the receiver continuously decreases with distance away from the GC path, becoming insignificant beyond approximately 20 lambda . On or near the GC path, the magnitude of the scattered signal was proportional to the scale of the perturbation parallel to the GC path }, keywords={ atmospheric electromagnetic wave propagation atmospheric electron precipitation atmospheric ionisation D-region ionospheric electromagnetic wave propagation plasma radiowave propagation upper atmosphere D-region lightning-induced perturbations night-time D-region single-mode VLF wave propagation received signal amplitude changes signal phase changes positive phase shifts negative phase shifts negative amplitude shifts scattered radio signal strength ionisation perturbation location perturbation scale size single waveguide mode theory subionospheric VLF propagation localized perturbations VLF signal Palmer Station Antarctica NPM transmitter Hawaii energetic electron precipitation events negative amplitude shifts single-mode signal 23.4 kHz }, mynotes={UNREAD}, } @ARTICLE{ImhofAug89, author={Imhof, W.L. and Voss, H.D. and Mobilia, J. and Walt, M. and Inan, U.S. and Carpenter, D.L.}, title={ Characteristics of short-duration electron precipitation bursts and their relationship with VLF wave activity }, journal={Journal of Geophysical Research}, volume={94}, number={A8}, year={1989}, month={Aug}, pages={10079-93}, abstract={ Energetic (>6 keV) electron data from the SEEP payload on the low altitude ( approximately 200 km) polar orbiting S81-1 satellite indicate a high rate of occurrence of short duration (<0.6 s) electron precipitation bursts. Characteristics of events observed at night (2230 MLT) versus daytime (1030 MLT) and at midlatitudes (23) were distinctly different in several ways. Comparison of the electron data with simultaneous VLF wave data from Palmer (L approximately=2.4) and Siple (L approximately=4.3) stations in Antarctica indicated a varying degree of association of electron bursts with whistlers and chorus emissions. Several of the electron bursts observed at nighttime and at 23) were observed on satellite passes within +or-50 degrees of the Siple meridian, chorus was invariably detected at Siple, but correlation of electron bursts with individual chorus spectral elements was not evident }, keywords={ atmospheric electron precipitation whistlers radiowave emission magnetosphere ionosphere short-duration electron precipitation bursts VLF wave activity whistlers chorus lightning-generated }, mynotes={UNREAD}, } @ARTICLE{SonwalkarJun89, author={Sonwalkar, V.S. and Inan, U.S.}, title={ Lightning as an embryonic source of VLF hiss }, journal={Journal of Geophysical Research}, volume={94}, number={A6}, year={1989}, month={Jun}, pages={6986-94}, abstract={ Data from the DE 1 satellite show that lightning-generated whistlers often trigger hiss emissions that endure for up to 10- and 20-s periods. The data consist of the measured electric and magnetic fields in the frequency range of 1.5 kHz to 6.0 kHz, during 22 DE 1 passes during the period December 28, 1986 to January 18, 1987. The 22 passes covered L shells of 3.4 to 5.1 and geomagnetic latitude of 20 degrees N to 40 degrees S in the afternoon ( approximately 1400-1500 MLT) sector. The whistler-triggered hiss emissions were observed on 16 of the passes, and they generally exhibited the following characteristics: emission spectra were wide band (1-2 kHz) and rather structureless; and well-defined and sustained fading patterns were observed at twice the spin frequency over 10- to 20-s periods. These results indicate that lightning-generated whistlers may be an important embryonic source for magnetospheric hiss and that whistlers and emissions triggered by them often constitute the dominant wave activity in the approximately 1.5- to 6-kHz range during geomagnetically quiet periods }, keywords={ atmospheric electron precipitation atmospheric proton precipitation atmospheric spectra atmospherics lightning magnetosphere radiation belts wideband structureless emission spectra ELF magnetosphere electric fields L-shells 3.4 to 5.1 afternoon sector wave normal angle trapped electrons loss ring current protons precipitation AD 1986 12 28 to 1987 01 18 VLF hiss DE 1 satellite lightning-generated whistlers hiss emissions magnetic fields DE 1 passes December 28, 1986 to January 18, 1987 geomagnetic latitude whistler-triggered hiss emissions sustained fading patterns spin frequency embryonic source magnetospheric hiss dominant wave activity geomagnetically quiet periods 1.5 to 6.0 kHz 3.4 to 5.1 Earthradii 0.5 to 50 keV }, mynotes={UNREAD}, } @ARTICLE{InanFeb89, author={Inan, U.S. and Walt, M. and Voss, H.D. and Imhof, W.L.}, title={ Energy spectra and pitch angle distributions of lightning-induced electron precipitation: analysis of an event observed on the S81-1 (SEEP) satellite }, journal={Journal of Geophysical Research}, volume={94}, number={A2}, year={1989}, month={Feb}, pages={1379-401}, abstract={ Temporal and spectral signatures of a lightning-induced electron precipitation (LEP) burst observed on the S81-1 (SEEP) satellite are analyzed and compared with the predictions of a test particle model of the gyroresonant whistler-particle interaction in the magnetosphere. The flux to be detected by specific detectors on the low altitude ( approximately 220 km) satellite at L approximately=2.24 is calculated in terms of the integral counting rate as a function of time and in terms of the dynamic energy spectra during the initial approximately 300-ms precipitation pulse. For a whistler wave packet with frequency range 500 Hz to 6 kHz the dynamic energy spectra are found to depend sensitively on the electron angular distribution in the vicinity of the loss cone. In the case of a whistler wave originating in northern hemisphere lightning the maximum whistler-induced pitch angle scattering of electrons occurs near approximately 10 degrees S geomagnetic latitude }, keywords={ atmospheric electron precipitation ionosphere magnetosphere ionosphere wave particle interaction pitch angle distributions lightning-induced electron precipitation burst test particle model gyroresonant whistler-particle interaction magnetosphere whistler wave }, mynotes={UNREAD}, } @ARTICLE{GurnettMay88, author={Gurnett, D.A. and Inan, U.S.}, title={ Plasma wave observations with the Dynamics Explorer 1 spacecraft }, journal={Reviews of Geophysics}, volume={26}, number={2}, year={1988}, month={May}, pages={285-316}, abstract={ Reviews the results from the plasma wave instrument on the Dynamics Explorer 1 (DE 1) spacecraft. The DE 1 spacecraft was launched on August 3, 1981, into an elliptical polar orbit with initial perigee and apogee radial distances of 1.09 and 4.65 R/sub E/. In the roughly 6 years since the launch of the spacecraft, DE 1 has provided basic new information on a wide variety of magnetospheric plasma wave phenomena. These include auroral kilometric radiation, auroral hiss, Z mode radiation, narrow-band electromagnetic emissions associated with equatorial upper hybrid waves, whistler mode emissions, wave-particle interactions stimulated by ground VLF transmitters, equatorial ion cyclotron emissions, ion Bernstein mode emissions, and electric field turbulence along the auroral field lines. The authors first give a brief review of the basic plasma wave modes that can exist in the equatorial and polar regions of the magnetosphere. After the basic terminology is established, each of the above areas of plasma wave research is discussed in detail }, keywords={ magnetosphere reviews AD 1981 to 1987 DE satellite plasma wave ionosphere magnetosphere EM wave radiowave emissions Dynamics Explorer 1 auroral kilometric radiation auroral hiss Z mode radiation narrow-band electromagnetic emissions equatorial upper hybrid waves whistler mode emissions wave-particle interactions }, mynotes={UNREAD}, } @ARTICLE{InanOct88, author={Inan, U.S. and Shafer, D.C. and Yip, W.Y. and Orville, R.E.}, title={ Subionospheric VLF signatures of nighttime D region perturbations in the vicinity of lightning discharges }, journal={Journal of Geophysical Research}, volume={93}, number={A10}, year={1988}, month={Oct}, pages={11455-72}, abstract={ A 12-hour sequence of perturbations of subionospheric VLF signals observed in association with lightning provided preliminary evidence that the ionospheric regions perturbed in these events may be confined to within approximately 150 km of the lightning discharges, and that intracloud flashes as well as cloud-to-ground lightning may be important in producing the perturbations. High-resolution analysis of event signatures indicated the presence of two different classes of events. For one set of events, observed during the most active central 6 hours of the observation period, a approximately 0.6-s delay between the causative lightning and VLF event onset and a approximately 1-s onset duration was observed, consistent with previously suggested models of the gyroresonant whistler-particle interaction that leads to particle precipitation and perturbation of the Earth-ionosphere waveguide. However, another set of events, observed during the first 2 hours of the observation period, exhibited a very different temporal signature, characterized by a much smaller (<50 ms) delay and sometimes also very short (<50 ms) rise times }, keywords={ atmospheric radiation D-region lightning whistlers night radiowave emission D-region ionosphere perturbation AD 1987 03 nighttime lightning discharges subionospheric VLF signals gyroresonant whistler-particle interaction particle precipitation Earth-ionosphere waveguide }, mynotes={UNREAD}, } @ARTICLE{InanSep88, author={Inan, U.S. and Wolf, T.G. and Carpenter, D.L.}, title={ Geographic distribution of lightning-induced electron precipitation observed as VLF/LF perturbation events }, journal={Journal of Geophysical Research}, volume={93}, number={A9}, year={1988}, month={Sep}, pages={9841-53}, abstract={ Expected occurrence characteristics of lightning-induced electron precipitation (LEP) events at longitudes of the western (110 degrees W) versus eastern (71 degrees W) United States are considered from the point of view of available trapped particle flux at the edge of the loss cone. Considering published data on nighttime fluxes of >68 keV electrons observed at L approximately=2.5, and for 'direct' precipitation into the northern hemisphere induced by northern hemisphere lightning, the occurrence rate and flux levels are expected to be a factor of 20-200 higher in the west than in the east, assuming no significant variation in lightning source activity with longitude. Again assuming lightning sources in the north, it is predicted that at 71 degrees W, 'mirrored' precipitation into the southern hemisphere would involve precipitation fluxes 30-300 times higher than 'direct' precipitation into the northern hemisphere. However, at 110 degrees W and again assuming lightning in the north, southern hemisphere precipitation would tend to be limited to that small fraction of particles that were initially scattered into the northern loss cone and that were then backscattered from the northern atmosphere so as to reach the south }, keywords={ atmospheric electron precipitation ionosphere magnetosphere atmospherics LEP ionosphere magnetosphere lightning-induced electron precipitation United States available trapped particle flux occurrence rate }, mynotes={UNREAD}, } @ARTICLE{SonwalkarJul88, author={Sonwalkar, V.S. and Inan, U.S.}, title={ Wave normal direction and spectral properties of whistler mode hiss observed on the DE 1 satellite }, journal={Journal of Geophysical Research}, volume={93}, number={A7}, year={1988}, month={Jul}, pages={7493-514}, abstract={ A new study of magnetospheric hiss as a spatially and temporally enduring phenomenon is undertaken using a recently developed formalism that allows the representation of hiss by a field distribution function (FDF). This formalism explicitly takes into account the whistler mode relationships and the linear and spin motion of the satellite, so that on a spin-stabilized satellite, it becomes possible to measure the wave propagation direction(s) from the observed fading patterns in the received electromagnetic field data. The authors have analyzed hiss signals received by electric and magnetic field antennae aboard the DE 1 satellite during a approximately 3-hour period on September 23, 1983. A band of hiss at frequencies <2 kHz was observed continuously from 0236 UT t0 0539 UT over a range of geomagnetic latitudes from lambda /sub m/=45 degrees N to lambda /sub m/=20 degrees S and L shells of L=4.3 to L=5.3. Electron density deduced from in situ and remote measurements indicate that during this time the DE 1 satellite was near the boundary of the plasmasphere. The observations are summarized }, keywords={ atmospheric radiation magnetosphere whistlers radiowave emission wave normal direction magnetosphere ELF AD 1983 09 23 VLF spectral properties whistler mode hiss magnetospheric hiss field distribution function formalism wave propagation direction boundary plasmasphere 1 to 4 kHz }, mynotes={UNREAD}, } @ARTICLE{InanFeb88, author={Inan, U.S. and Burgess, W.C. and Wolf, T.G. and Shafer, D.C. and Orville, R.E.}, title={ Lightning-associated precipitation of MeV electrons from the inner radiation belt }, journal={Geophysical Research Letters}, volume={15}, number={2}, year={1988}, month={Feb}, pages={172-5}, abstract={ Transient perturbations of subionospheric very low frequency radiowave signals provide new evidence for lightning-induced electron precipitation events involving (<1 s) bursts of >1 MeV electrons from the Earth's inner radiation belt at L30. The emissions may be generated near the equatorial plane at frequencies of approximately 0.2 F/sub Heq/ inside and approximately 0.35 f/sub Heq/ outside the plasmapause. The parallel energy of electrons for gyroresonance with the observed waves is found to be approximately 20-50 keV in both cases }, keywords={ atmospherics dispersion (wave) ionospheric electromagnetic wave propagation magnetic storms magnetosphere magnetospheric electromagnetic wave propagation whistlers emission elements bandwidth K/sub p/-index plasmasphere burstlike emissions emission elements dispersion equatorial whistlers source ISIS-2 satellite gyroresonant electrons parallel energy ionospheric reflections discrete VLF emission discrete whistler mode emission magnetosphere lower cutoff frequency equatorial electron gyrofrequency chorus emissions plasmapause early morning local time sector geomagnetic activity equatorial plane 1 to 5 kHz 5 to 25 kHz 2 to 4 Earthradii }, mynotes={UNREAD}, } @ARTICLE{InanApr87, title={ Waves and instabilities }, journal={Reviews of Geophysics}, volume={25}, number={3}, year={1987}, month={Apr}, pages={588-98}, abstract={ This review concentrates on US research activities in the area of waves and instabilities during the mid-1982 to mid-1986 period. Plasma waves and instabilities are phenomena that are central to the energization, acceleration, transport, and loss of energetic particles in magnetized plasmas. As such, they play a dominant role in almost all energy exchange phenomena that occur in planetary magnetospheres. The US research can be somewhat arbitrarily divided into the following six categories: (1) whistler mode wave-electron interactions, (2) wave-induced particle precipitation, (3) ULF wave phenomena, (4) ion-mode waves and instabilities, (5) auroral kilometric radiation, (6) ionospheric irregularities and instabilities, and (7) waves and instabilities in the outer magnetosphere }, keywords={ ionosphere magnetosphere reviews plasma wave magnetosphere plasma stability whistler mode wave-electron interactions wave-induced particle precipitation ULF wave phenomena ionospheric }, mynotes={UNREAD}, } @ARTICLE{CarpenterApr87, author={Carpenter, D.L. and Inan, U.S.}, title={ Seasonal, latitudinal and diurnal distributions of whistler-induced electron precipitation events }, journal={Journal of Geophysical Research}, volume={92}, number={A4}, year={1987}, month={Apr}, pages={3429-35}, abstract={ The seasonal, latitudinal, and diurnal distributions of whistler-induced electron precipitation events, detected as subionospheric signal perturbations (Trimpi events), have been studied by means of data sets acquired in 1982-3 at Palmer and Siple stations, Antarctica. The authors also compare simultaneous records from L approximately 2.4 and L approximately 4.3, and find evidence of an inner magnetospheric maximum in burst precipitation activity for E>40 keV in the range L approximately 2-3, consistent with theoretical predictions }, keywords={ atmospheric electron precipitation whistlers AD 1982 to 1983 VLF seasonal variation latitudinal variation diurnal distributions whistler-induced electron precipitation events subionospheric signal perturbations Trimpi events Palmer Siple Antarctica inner magnetospheric maximum burst precipitation activity }, mynotes={UNREAD}, } @ARTICLE{InanApr87, author={Inan, U.S. and Carpenter, D.L.}, title={ Lightning-induced electron precipitation events observed at L approximately 2.4 as phase and amplitude perturbations on subionospheric VLF signals }, journal={Journal of Geophysical Research}, volume={92}, number={A4}, year={1987}, month={Apr}, pages={3293-303}, abstract={ Lightning-induced electron precipitation (LEP) events are studied using the Trimpi effect, in which the precipitation-induced ionization enhancements in the lower ionosphere (D region) give rise to rapid perturbations of subionospheric VLF signals. In 1983, the phase and amplitude of signals from the NPM transmitter in Hawaii (23.4 kHz) and the Omega transmitter in Argentina (12.9 kHz) were measured at Palmer, Antarctica (L approximately 2.4), together with the magnetospheric whistler background. The long baseline and over-sea great circle paths from these two sources make it possible for the observed perturbations to be interpreted using a single waveguide mode theory. Analytical expressions are used to relate the magnitude of the phase perturbations to differential changes in ionospheric reflection height along a segment of the propagation path. The predicted relationship between relative perturbation sizes on the two different signals is compared with measurements. From this information, the whistler-induced flux levels are inferred to be in the 10/sup -4/-10/sup -2/ erg cm/sup -2/ s/sup -1/ range and the precipitation regions are inferred to be roughly 'circular' in shape, rather than elongated along L shells }, keywords={ atmospheric electron precipitation ionospheric electromagnetic wave propagation AD 1983 phase perturbation radiowave propagation lightning induced ionosphere D-region electron precipitation events amplitude perturbations subionospheric VLF signals Trimpi effect precipitation-induced ionization enhancements lower ionosphere whistler }, mynotes={UNREAD}, } @ARTICLE{HurrenAug86, author={Hurren, P.J. and Smith, A.J. and Carpenter, D.L. and Inan, U.S.}, title={ Burst precipitation induced perturbations on multiple VLF propagation paths in Antarctica }, journal={Annales Geophysicae, Series A (Upper Atmosphere and Space Sciences)}, volume={4}, number={4}, year={1986}, month={Aug}, pages={311-18}, abstract={ The burst precipitation of energetic (E>40 keV) electrons near L=4 has been detected as amplitude perturbations (Trimpi events) on subionospheric 3.79 kHz CW signals from the Siple (L=4.2) VLF transmitter that were observed at Halley (L/sup -/=4.3), Palmer (L=2.3) and South Pole ( Lambda =74 degrees ) Antarctic stations. The observations were made on the dayside of the Earth but beneath a locally dark ionosphere during a generally disturbed 6 d period in July 1982 when the plasmapause projection was equatorward of the Siple-Halley and Siple-South Pole paths }, keywords={ atmospheric electron precipitation ionospheric electromagnetic wave propagation radiowave propagation ionosphere radiowave energetic electrons AD 1982 07 12 to 17 multiple VLF propagation paths Antarctica burst precipitation amplitude Trimpi events CW signals Siple Halley Palmer South Pole plasmapause projection 3.79 kHz }, mynotes={UNREAD}, } @ARTICLE{InanJan87, title={ Gyroresonant pitch angle scattering by coherent and incoherent whistler mode waves in the magnetosphere }, journal={Journal of Geophysical Research}, volume={92}, number={A1}, year={1987}, month={Jan}, pages={127-42}, abstract={ A test particle approach is used to compare gyroresonant pitch angle scattering of energetic electrons by coherent versus incoherent whistler mode waves, for the case in which the coherent wave amplitude is below the nonlinear phase trapping threshold. Wave packets of 400 ms duration propagating along the magnetic field at L=4 within the plasmasphere are considered, and the wave-induced pitch angle scattering along the propagation path from one hemisphere to the other and the resulting precipitation flux are computed. An incoherent wave spectrum is simulated by random modulation of the wave frequency at intervals of 1 ms, thereby generating signals with nearly constant power spectral density over a bandwidth of 2 kHz centered at 5.5 kHz. The associated pitch angle scattering is compared with that of a monochromatic 5.5 kHz signal of 400 ms duration. Results of the test particle analysis are compared with those expected on the basis of a classical diffusion treatment }, keywords={ atmospheric elementary particle precipitation magnetospheric electromagnetic wave propagation plasma radiation belts whistlers EM wave atmosphere VLF radiation belt plasma incoherent whistler mode waves magnetosphere test particle approach gyroresonant pitch angle scattering energetic electrons coherent wave amplitude nonlinear phase trapping threshold magnetic field plasmasphere precipitation flux wave spectrum random modulation wave frequency power spectral density classical diffusion treatment 5.5 kHz }, mynotes={UNREAD}, } @ARTICLE{TolstoyDec86, author={Tolstoy, A. and Rosenberg, T.J. and Inan, U.S. and Carpenter, D.L.}, title={ Model predictions of subionospheric VLF signal perturbations resulting from localized, electron precipitation-induced ionization enhancement regions }, journal={Journal of Geophysical Research}, volume={91}, number={A12}, year={1986}, month={Dec}, pages={13473-82}, abstract={ Whistler-induced precipitation of energetic electrons produces transient ionospheric conductivity variations that perturb the amplitude and phase of VLF signals propagating in the Earth-ionosphere waveguide. This study uses a waveguide mode theoretic propagation model to predict the effect of localized ionization enhancement (IE) regions on nighttime long-path VLF signals from the US Navy navigational transmitters NSS, NAA, NLK and NPM to Antarctic receiving stations. The predictions are then compared with the observed signal behavior in Trimpi events from which inferences can be drawn about an IE region's approximate characteristics. The study also examines the effects of transmitter-induced electron precipitation on the VLF signals }, keywords={ atmospheric electricity atmospheric electron precipitation atmospheric ionisation ionosphere ionospheric electromagnetic wave propagation radiowave propagation D-region whistlers atmosphere radiowave subionospheric VLF signal perturbations electron precipitation-induced ionization enhancement regions transient ionospheric conductivity variations amplitude phase Earth-ionosphere waveguide propagation nighttime US Navy navigational transmitters Antarctic receiving stations Trimpi events }, mynotes={UNREAD}, } @ARTICLE{InanApr86, title={ Jovian VLF chorus and Io torus aurora }, journal={Journal of Geophysical Research}, volume={91}, number={A4}, year={1986}, month={Apr}, pages={4543-50}, abstract={ A test particle model of the cyclotron resonance interaction of waves and trapped radiation belt particles is used to estimate the energetic electron fluxes precipitated by Jovian VLF chorus waves observed on the Voyager 1 and 2 spacecraft near the Io torus. The precipitation fluxes induced by 1-s-long chorus wave packets at L approximately=7.6 and 8.6 are estimated to be bursts of approximately 5 s duration with a peak of 0.3-3 and 0.7-7 ergs/cm/sup 2/ s that consist of electrons of approximately 5-100 keV energy and that arrives at the ionosphere approximately 15 s after the generation of the chorus wave at the equatorial plane. The effects in the Jovian ionosphere of the chorus-induced precipitation are estimated using existing ionospheric models }, keywords={ Jupiter planetary atmospheres planetary satellite atmospheres Jupiter planetary atmosphere radiowave emission plasma torus magnetosphere electron precipitation VLF chorus Io torus aurora test particle model cyclotron resonance interaction radiation belt energetic electron fluxes ionosphere }, mynotes={UNREAD}, } @ARTICLE{HelliwellApr86, author={Helliwell, R.A. and Carpenter, D.L. and Inan, U.S. and Katsufrakis, J.P.}, title={ Generation of band-limited VLF noise using the Siple transmitter: a model for magnetospheric hiss }, journal={Journal of Geophysical Research}, volume={91}, number={A4}, year={1986}, month={Apr}, pages={4381-92}, abstract={ Band-limited VLF noise generated by the experimental transmitter at Siple Station, Antarctica, is used to simulate the interaction of natural magnetospheric hiss with energetic radiation belt particles. While the observed spectrum of the generated noise at times closely resembles that of natural VLF hiss, at other times discrete emissions are found to be generated from the incoherent noise signal. Results imply that magnetospheric chorus can be triggered by hiss signals, indicating the similarity of generation mechanisms for coherent and incoherent VLF emissions. A model based on second-order cyclotron resonance can explain the conversion of the relatively short duration wavelets of a hiss spectrum into the longer, semicoherent discrete emissions that are typical of chorus }, keywords={ magnetosphere radiowave emission generation wave particle interaction band-limited VLF noise model magnetospheric hiss interaction natural radiation belt particles discrete emissions chorus generation mechanisms }, mynotes={UNREAD}, } @ARTICLE{InanMar86, author={Inan, U.S. and Carpenter, D.L.}, title={ On the correlation of whistlers and associated subionospheric VLF/LF perturbations }, journal={Journal of Geophysical Research}, volume={91}, number={A3}, year={1986}, month={Mar}, pages={3106-16}, abstract={ Several periods of whistler-associated subionospheric signal perturbations (i.e. Trimpi events) observed at Palmer, Antarctica (L approximately 2.4) have been studied. In a case study of the time signature of the signal perturbations during a 10-min recording period on March 30, 1983, the time delay between the whistler-producing spheric and the onset of the change was found to be in the range 0.52-0.62 s, independent of the amplitude of the change. Event amplitude, as expected from previous work, was found to be well correlated with the associated whistler wave intensity. Other temporal features such as the rise and decay times of the perturbations were also found to be independent of the event amplitude. These results are consistent with a recent theoretical model of gyroresonant particle scattering interaction in the magnetosphere }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation whistlers associated subionospheric perturbations VLF LF magnetosphere AD 1983 03 Trimpi event correlation whistlers spheric onset gyroresonant particle scattering interaction magnetosphere }, mynotes={UNREAD}, } @ARTICLE{SonwalkarJan86, author={Sonwalkar, V.S. and Inan, U.S.}, title={ Measurements of Siple transmitter signals on the DE 1 satellite: wave normal direction and antenna effective length }, journal={Journal of Geophysical Research}, volume={91}, number={A1}, year={1986}, month={Jan}, pages={154-64}, abstract={ A new experimental technique is developed to simultaneously measure the wave propagation direction and the effective length of a small (L<< lambda ) electric dipole antenna on a spin stabilized satellite in the magnetosphere. The technique relies on the near simultaneous measurement of single components of the electric and magnetic fields of a coherent VLF signal injected into the medium from a ground-based source. The spin fading characteristics of the signal received by the electric dipole and the magnetic loop antenna permit the measurement of the wave normal direction. Measurements of the local cold plasma density are used to determine the refractive index. The wave electric field is then inferred from the wave magnetic field as measured on the loop antenna, the refractive index and the direction of propagation. Comparing this electric field with the measured voltage across the dipole antenna leads to the effective length of the receiving electric dipole }, keywords={ artificial satellites atmospheric electricity atmospheric techniques geomagnetism magnetosphere magnetospheric electromagnetic wave propagation whistlers VLF whistler mode signals small dipole antenna magnetosphere EM wave propagation HZ 4025 signal electric fields components AD 1982 07 28 dipole antenna voltage magnetospheric technique Earth radii 004.5 to 005.5 Siple transmitter signals DE 1 satellite wave normal direction antenna effective length wave propagation direction electric dipole antenna spin stabilized satellite near simultaneous measurement single components magnetic fields coherent VLF signal ground-based source spin fading characteristics magnetic loop antenna local cold plasma density refractive index wave electric field wave magnetic field receiving electric dipole }, mynotes={UNREAD}, } @ARTICLE{HelliwellJan86, author={Helliwell, R.A. and Inan, U.S. and Katsufrakis, J.P. and Carpenter, D.L.}, title={ Beat excitation of whistler mode sidebands using the Siple VLF transmitter }, journal={Journal of Geophysical Research}, volume={91}, number={A1}, year={1986}, month={Jan}, pages={143-53}, abstract={ The process of whistler mode sideband generation in the magnetosphere is studied by transmitting two monochromatic signals closely spaced in frequency ( Delta f=5-45 Hz) from the experimental VLF transmitter at Siple Station, Antarctica. The signals were observed following ducted magnetospheric propagation to the conjugate station at Roberval, Quebec. Sidebands up to seventh order were generated extending to +or-100 Hz with respect to the average frequency of the carriers. New frequencies were observed both under conditions of little or no growth of the input signals and when one of the input signals did grow significantly. A small signal mechanism is proposed in which emissions are triggered by each beat between the input waves but are then suppressed by the following beat. The energy from the phase bunched particles is believed to feed preferentially into the sidebands. The observed process of sideband generation provides a mechanism to break down the coherence of relatively narrowband waves in the magnetosphere and may account for the transformation of relatively coherent wave packets into broader more variable bands of noiselike signals }, keywords={ atmospherics magnetosphere magnetospheric electromagnetic wave propagation whistlers whistler sidebands beat excitation ELF atmospherics magnetosphere EM wave propagation two-frequency signal seventh-order sidebands carriers average frequency input signals growth rate phase bunched particles energy VLF emissions triggering Hz 2200 to 3800 AD 1983 06 30 AD 1983 07 11 Siple VLF transmitter whistler mode sideband generation monochromatic signals Siple Station Antarctica ducted magnetospheric propagation conjugate station Roberval Quebec small signal mechanism relatively coherent wave packets noiselike signals }, mynotes={UNREAD}, } @ARTICLE{DejnakarintraDec85, author={Dejnakarintra, M. and Inan, U.S. and Carpenter, D.L.}, title={ Transient tropospheric electric fields resulting from sudden changes in ionospheric conductivity }, journal={Journal of Geophysical Research}, volume={90}, number={A12}, year={1985}, month={Dec}, pages={12271-81}, abstract={ The transient electric fields that would be generated by sudden changes in the atmospheric conductivity profile are estimated using a theoretical model. The model assumes the existence of a horizontal electric field with a spatial extent of >or=20-km at 150-km altitude and involves the solution of the boundary value problem in two dimensions. The geomagnetic field lines below 150-km altitude are assumed to be vertical, but the anisotropy of the medium above approximately 70-km altitude is fully accounted for. The computed electric field strength depends sensitively on the size of the source field as well as the conductivity profile of the atmosphere. During a transient the peak electric fields produced in the case of a small-scale source field can be considerably larger than those due to large-scale source distributions }, keywords={ atmospheric electricity troposphere troposphere transient electric field atmosphere electrical conductivity sudden changes ionospheric conductivity theoretical model horizontal electric field boundary value problem source field }, mynotes={UNREAD}, } @ARTICLE{InanAug85, author={Inan, U.S. and Carpenter, D.L. and Helliwell, R.A. and Katsufrakis, J.P.}, title={ Subionosphere VLF/LF phase perturbations produced by lightning-whistler induced particle precipitation }, journal={Journal of Geophysical Research}, volume={90}, number={A8}, year={1985}, month={Aug}, pages={7457-69}, abstract={ New evidence of phase perturbations of subionospheric VLF/LF signals, produced by lightning-whistler-induced precipitation of bursts of radiation belt electrons, is reported. Phase changes of 0.1-1.0 mu s on a 12.9-kHz signal arriving at Palmer, Antarctica (L approximately 2.4), over a approximately 2400-km path are regularly observed with a characteristic signature of a rapid (or=50 keV) into the nighttime lower ionosphere. The receiving stations, each approximately 1400 km from Siple, were located to the north at Palmer (L approximately 2.3), to the east at Halley (L approximately 4.3), and to the south at South Pole ( Lambda approximately 74 degrees ). Rapid changes in the received phase and amplitude of the Siple signal ('Trimpi events') were observed in conjunction with the reception of one-hop whistlers. Phase measurements appear to be a particularly sensitive means of detecting burst precipitation activity under experimental conditions of the kind described. The length and spatial distribution of the signal paths provide a basis for studying the occurrence and approximate location of burst precipitation in regions outside the observing range of most instruments used for detection of precipitation }, keywords={ atmospheric electron precipitation ionospheric techniques electron precipitation measurement technique ionosphere VLF method burst precipitation plasmapause occurrence nighttime lower ionosphere phase occurrence approximate location }, mynotes={UNREAD}, } @ARTICLE{InanJan85, author={Inan, U.S. and Chang, H.C. and Helliwell, R.A. and Imhof, W.L. and Reagan, J.B. and Walt, M.}, title={ Precipitation of radiation belt electrons by man-made waves: a comparison between theory and measurement }, journal={Journal of Geophysical Research}, volume={90}, number={A1}, year={1985}, month={Jan}, pages={359-69}, abstract={ The temporal and spectral shape and the absolute flux level of particle pulses precipitated by a VLF transmitter are examined from a theoretical point of view. A test-particle model of the gyroresonant wave-particle interactions is applied to the parameters of the observed cases for calculating the precipitation characteristics. The temporal shapes of the precipitation pulses are found to be controlled (1) by the pitch angle dependence of the particle distribution near the edge of the loss cone and (2) by the multiple interaction of the particles with the waves due to significant atmospheric backscatter }, keywords={ atmospheric electron precipitation magnetosphere radiation belts radiowave propagation magnetosphere electron precipitation artificial modification experiment transmitter induced radiation belt electrons man-made waves theory VLF test-particle model gyroresonant wave-particle interactions precipitation pulses }, mynotes={UNREAD}, } @ARTICLE{SmithJan85, author={Smith, A.J. and Carpenter, D.L. and Inan, U.S.}, title={ Whistler-triggered VLF noise bursts observed on the DE-1 satellite and simultaneously at Antarctic ground stations }, journal={Annales Geophysicae}, volume={3}, number={1}, year={1985}, month={Jan}, pages={81-8}, abstract={ Whistler-triggered bursts of very low frequency chorus in the 5-7 kHz range, occurring quasi-periodically every 3-5 min, have previously been observed at ground stations under conditions of relatively deep quieting following moderate magnetic disturbance. It was found that these wave bursts propagate outside the plasmapause and that they can induce detectable electron precipitation at ionospheric D-region altitudes. This paper reports simultaneous observations of such wave events on the ground at Antarctic stations Halley and Siple (L=4.3) and on the high altitude satellite DE-1 }, keywords={ atmospherics magnetosphere whistlers whistler-triggering chorus kHz 0005 to 0007 ducted propagation VLF noise bursts DE-1 satellite Antarctic ground stations electron precipitation ionospheric D-region Halley Siple high altitude satellite }, mynotes={UNREAD}, } @ARTICLE{InanFeb85, author={Inan, U.S. and Bell, T.F.}, title={ Spectral broadening of VLF transmitter signals observed on DE 1: a quasi-electrostatic phenomenon? }, journal={Journal of Geophysical Research}, volume={90}, number={A2}, year={1985}, month={Feb}, pages={1771-5}, abstract={ Spectrally broadened VLF transmitter signals are observed on the DE 1 satellite using alternatively both electric and magnetic field sensors. It is found that at times when the electric field component undergoes significant bandwidth expansion (up to approximately 110 Hz) the magnetic field component has a bandwidth of less than 10 Hz. The results support the theory that the off-carrier components are quasi-electrostatic in nature. Measurement of the absolute E and B field magnitudes of the broadened signals are used to determine the wave Poynting vector }, keywords={ ionospheric electromagnetic wave propagation radiowave propagation radiowave propagation quasielectrostatic ionosphere spectral broadening offcarrier transionospheric VLF transmitter signals theory off-carrier wave Poynting vector }, mynotes={UNREAD}, } @ARTICLE{ChangFeb85, author={Chang, H.C. and Inan, U.S.}, title={ Lightning-induced electron precipitation from the magnetosphere }, journal={Journal of Geophysical Research}, volume={90}, number={A2}, year={1985}, month={Feb}, pages={1531-41}, abstract={ Precipitation of radiation belt particles induced by whistlers that are generated by atmospheric lightning discharges and propagate over L shells of 2-4.5 is considered. Using a test particle model of the whistler-particle interaction, the energy spectra and temporal profile of whistler-induced fluxes as a function of L shell are quantitatively determined for representative plasmaspheric cold plasma distribution. Results indicate that for higher energy electron precipitation (E>40 keV) there exists an inner magnetospheric region (250 on the active VLF paths. The MF perturbations were of order 50% in amplitude and were not in general followed by a approximately 30-s decay toward a pre-event level, as is usually the case for the VLF signals }, keywords={ atmospheric electron precipitation ionospheric electromagnetic wave propagation radiowave propagation whistlers LF radiowave propagation ionosphere subionospheric MF whistler-induced electron precipitation bursts }, mynotes={UNREAD}, } @ARTICLE{TkalcevicDec84, author={Tkalcevic, S. and Inan, U.S. and Helliwell, R.A.}, title={ Nonlinear pitch angle scattering and trapping of energetic particles during Landau resonance interactions with whistler mode waves }, journal={Journal of Geophysical Research}, volume={89}, number={A12}, year={1984}, month={Dec}, pages={10813-26}, abstract={ The time averaged equations of motivation derived by Inan and Tkalcevic (1982) are used in a test particle study of Landau resonant interactions of whistler mode waves and energetic particles in the magnetosphere. By computing individual particle trajectories it is shown that the pitch angle scattering and energy exchange is significantly different for the two classes of particles, trapped and untrapped. The trapped particles are characterized by a bounded phase variation, whereas the nontrapped particles exhibit unbounded phase variation. The threshold wave electric field intensities necessary for trapping are determined. Full distribution test particle simulation is carried out to determine the precipitated electron flux that would be induced as a result of these interactions }, keywords={ atmospheric electron precipitation magnetosphere whistlers nonlinear trapped particle EM wave wave particle interaction pitch angle scattering trapping energetic particles Landau resonance interactions whistler mode waves equations of motivation energy exchange untrapped nontrapped }, mynotes={UNREAD}, } @ARTICLE{LeyserOct84, author={Leyser, T.B. and Inan, U.S. and Carpenter, D.L. and Trimpi, M.L.}, title={ Diurnal variation of burst precipitation effects on subionospheric VLF/LF signal propagation near L=2 }, journal={Journal of Geophysical Research}, volume={89}, number={A10}, year={1984}, month={Oct}, pages={9139-43}, abstract={ Burst precipitation effects on subionospheric VLF/LF signal propagation are studied using data recorded at Palmer Station, Antarctica (L approximately 2.4) between March 3 and April 7, 1983. Relatively abrupt signal amplitude changes known as 'Trimpi' effects were observed in conjunction with magnetospheric whistlers, which are inferred to induce electron precipitation that in turn causes enhanced ionization at the 80 to 90-km altitude level. Earlier findings that Trimpi effects occur predominantly under nighttime ionospheric conditions were confirmed by comparing the sunrise-sunset terminator position with perturbation activity on three VLF/LF signal paths for which the arrival bearings range from magnetic north to west. Events were found to occur on 70% of the observing nights. Signal paths making larger angles with the terminator were used to deduce that most events were caused by ionospheric effects occurring within approximately 1000 km of Palmer Station }, keywords={ atmospheric electromagnetic wave propagation atmospheric electron precipitation atmospheric ionisation ionosphere ionospheric electromagnetic wave propagation upper atmosphere whistlers ionospheric disturbances upper atmosphere atmospheric EM wave propagation equinox electron precipitation events altitude km 0080 to 0090 ionospheric events distance AD 1983 03 03 to 04 07 kHz 0013 to 0780 precipitation effects diurnal variation burst precipitation effects subionospheric VLF/LF signal propagation Palmer Station Antarctica signal amplitude changes magnetospheric whistlers enhanced ionization 80 to 90-km altitude level Trimpi effects nighttime ionospheric conditions sunrise-sunset terminator position perturbation activity VLF/LF signal paths arrival bearings }, mynotes={UNREAD}, } @ARTICLE{SonwalkarMay84, author={Sonwalkar, V.S. and Bell, T.F. and Helliwell, R.A. and Inan, U.S.}, title={ Direct multiple path magnetospheric propagation: a fundamental property of nonducted VLF waves }, journal={Journal of Geophysical Research}, volume={89}, number={A5}, year={1984}, month={May}, pages={2823-30}, abstract={ ISEE 1 satellite observations of nonducted whistler mode signals from the Siple Station VLF transmitter show that all well-defined pulses are elongated by 20 ms to 200 ms. This elongation is attributed to closely spaced multiple paths of propagation between the ground and the satellite. The results are illustrated by two cases: one on October 29, 1977, inside the plasmapause and the other on May 7, 1979, outside the plasmapause. The results establish that, in general, at any point in the magnetosphere the direct signals transmitted from the ground arrive almost simultaneously along two or more closely spaced direct ray paths. It is shown that multiple paths can be explained by assuming field-aligned irregularities of 1 to 10-km horizontal scale in the ionosphere with a few percent enhancement or depletion in the plasma density }, keywords={ atmospheric ionisation ionosphere ionospheric electromagnetic wave propagation magnetospheric electromagnetic wave propagation plasma whistlers direct multiple path magnetospheric propagation pulse elongation EM wave propagation atmospheric ionisation AD 1977 10 29 plasma density irregularities characteristic size AD 1979 05 07 wave-particle interactions cyclotron resonant electron wave Doppler broadening nonducted VLF waves ISEE 1 satellite observations whistler mode signals Siple Station VLF transmitter closely spaced multiple paths October 29, 1977 plasmapause May 7, 1979 direct ray paths field-aligned irregularities horizontal scale ionosphere }, mynotes={UNREAD}, } @ARTICLE{InanMay84, author={Inan, U.S. and Chang, H.C. and Helliwell, R.A.}, title={ Electron precipitation zones around major ground-based VLF signal sources }, journal={Journal of Geophysical Research}, volume={89}, number={A5}, year={1984}, month={May}, pages={2891-906}, abstract={ The spatial distribution of electron precipitation induced by VLF signals from ground-based transmitters is determined by using a test particle computer model of the gyroresonant wave-particle interaction (Inan et al., 1982). The results are presented as contours of energy flux on a map of the region around each transmitter. It is shown that the size of the precipitation zones is a strong function of the geographic location of the transmitter, as well as its radiated power and operating frequency. In general, the precipitation zones are much wider in longitude than in latitude and are oriented along lines of constant geomagnetic latitude. Assuming backscatter and/or wave echoing, precipitation zones around the points that are magnetically conjugate to the sources are also estimated. The results presented can be used to interpret satellite- or ground-based measurements of the precipitation induced by ground-based VLF transmitters }, keywords={ atmospheric electron precipitation ionosphere magnetosphere magnetospheric electromagnetic wave propagation radiation belts whistlers geomagnetic parallels precipitation zones dimensions magnetically conjugate precipitation zones magnetosphere EM wave propagation whistler mode waves induced precipitation energy flux contours radiation belts particle losses ground-based VLF signal sources spatial distribution electron precipitation ground-based transmitters test particle computer model gyroresonant wave-particle interaction geographic location radiated power operating frequency constant geomagnetic latitude backscatter wave echoing }, mynotes={UNREAD}, } @ARTICLE{ChangDec83, author={Chang, H.C. and Inan, U.S.}, title={ A theoretical model study of observed correlations between whistler mode waves and energetic electron precipitation event in the magnetosphere }, journal={Journal of Geophysical Research}, volume={88}, number={A12}, year={1983}, month={Dec}, pages={10053-64}, abstract={ A recently extended test particle computer model of the gyroresonance wave-particle interaction in the magnetosphere is applied to previously reported cases of observed correlations between whistler mode waves and ionospheric responses to particle precipitation. Three different ionospheric effects, namely X-ray bursts, photoemissions, and D region perturbations, all correlated with VLF waves and believed to be caused by precipitated particles, are considered. The precipitation flux level, the pulse shape, and the associated time delays are computed for the parameters relevant to each case and are compared with values deduced from the data. The results demonstrate that the existing theoretical model can be useful for interpreting experimental results of this kind }, keywords={ atmospheric electron precipitation magnetosphere whistlers EM wave trapped particle wave particle interaction ionosphere theoretical model correlations whistler mode waves energetic electron precipitation event magnetosphere gyroresonance VLF waves }, mynotes={UNREAD}, } @ARTICLE{ChangSep83, author={Chang, H.C. and Inan, U.S. and Bell, T.F.}, title={ Energetic electron precipitation due to gyroresonant interactions in the magnetosphere involving coherent VLF waves with slowly varying frequency }, journal={Journal of Geophysical Research}, volume={88}, number={A9}, year={1983}, month={Sep}, pages={7037-50}, abstract={ A test particle simulation model (Inan et al., 1982) of the gyroresonance wave-particle interaction in the magnetosphere is extended to study the transient particle precipitation fluxes induced by various coherent VLF waves with slowly varying frequency propagating along the Earth's magnetic field lines. For moderate wave intensities (B/sub omega /1 the system is unstable and can generate self-excited oscillations. The self-excited oscillations reach saturation when G falls to unity, which occurs when the electron transit time through the interaction region is comparable with the phase bunching time. At signal levels well below saturation the model predicts exponential temporal growth }, keywords={ atmospheric radiation magnetosphere VLF radiowave emission triggering Doppler wave growth discrete emission magnetosphere feedback model cyclotron resonance narrowband whistler mode }, mynotes={UNREAD}, } @ARTICLE{BellMay82, author={Bell, T.F. and Luette, J.P. and Inan, U.S.}, title={ ISEE 1 observations of VLF line radiation in the Earth's magnetosphere }, journal={Journal of Geophysical Research}, volume={87}, number={A5}, year={1982}, month={May}, pages={3530-36}, abstract={ A search has been carried out for magnetospheric line radiation in the VLF data acquired during the period October 1977-August 1979. While the satellite position varied between L=2 and L=8 and the satellite longitude lay in the range 50 degrees W to 110 degrees W. This magnetospheric region encompassed the main regions in which the occurrence of VLF chorus has been actively linked to power line radiation. Line radiation was detected on only 5 of 90 orbits, and all examples occurred at frequencies below 4 kHz. Line radiation was detected during a period when whistler mode echoing was quite pronounced on lower L shells and may actually have been a scattered component of line radiation echoing between hemispheres on a magnetic shell of lower L value. It is concluded that very little of the background VLF wave energy in the outer magnetosphere is contained directly in VLF line radiation }, keywords={ atmospheric radiation magnetosphere radiowave emission AD 1977 to 1979 VLF line radiation magnetosphere }, mynotes={UNREAD}, } @ARTICLE{InanApr82, author={Inan, U.S. and Tkalcevic, S.}, title={ Nonlinear equations of motion for Landau resonance interactions with a whistler mode wave }, journal={Journal of Geophysical Research}, volume={87}, number={A4}, year={1982}, month={Apr}, pages={2363-7}, abstract={ A simple set of equations are derived for describing the cyclotron averaged motion of Landau resonant particles in a whistler mode wave propagating at an angle to the static magnetic field. It is argued that for the parameters of the inner magnetosphere, the equations would be an accurate description of the near-resonant particles' motion. The relative magnitudes of the wave magnetic and electric field forces are discussed and the parameter ranges for which the wave magnetic field effects can be neglected are specified }, keywords={ ionosphere magnetosphere whistlers nonlinear ionosphere wave particle interaction equations of motion Landau resonance interactions whistler mode wave cyclotron inner magnetosphere }, mynotes={UNREAD}, } @ARTICLE{BellOct81, author={Bell, T.F. and Inan, U.S.}, title={ Transient nonlinear pitch angle scattering of energetic electrons by coherent VLF wave packets in the magnetosphere }, journal={Journal of Geophysical Research}, volume={86}, number={A11}, year={1981}, month={Oct}, pages={9047-63}, abstract={ With the aid of adiabatic theory, a study is made of the transient nonlinear pitch angle scattering experienced by energetic electrons under the influence of coherent VLF wave packets in the magnetosphere. Finite wave packets of both fixed and variable frequency are considered, as are wide ranges of L shell, wave frequency, and wave amplitude. The results indicate that large mean pitch angle changes can be induced in the portion of the energetic population that undergoes a nonlinear cyclotron resonance interaction with the wave packet. Two classes of nonlinearly interacting particles are involved, the nonlinearly resonant particles trapped in the wave and the nonlinearly resonant nontrapped particles }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation radiowave propagation L-shell radiowave propagation energetic electrons coherent VLF wave packets magnetosphere adiabatic theory transient nonlinear pitch angle scattering wave frequency wave amplitude nonlinear cyclotron resonance interaction nonlinearly interacting particles nonlinearly resonant particles }, mynotes={UNREAD}, } @ARTICLE{BellJun81, author={Bell, T.F. and Inan, U.S. and Helliwell, R.A.}, title={ Nonducted coherent VLF waves and associated triggered emissions observed on the ISEE-1 satellite }, journal={Journal of Geophysical Research}, volume={86}, number={A6}, year={1981}, month={Jun}, pages={4649-70}, abstract={ Reports observations of non-ducted coherent VLF waves from ground-based transmitters and associated VLF emissions in the magnetosphere. The data reported were acquired by the Stanford University VLF Wave Injection Experiment on the ISEE-1 satellite. The aim is to acquire understanding of interactions between coherent VLF waves and energetic particles in the magnetosphere, in particular the whistler mode instability through which both natural and stimulated VLF emissions are produced }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation radiowave propagation radiowave propagation AD 1977 10 to 1979 10 triggered emissions non-ducted coherent VLF waves magnetosphere energetic particles whistler mode instability }, mynotes={UNREAD}, } @ARTICLE{InanJul78, author={Inan, U.S. and Bell, T.F. and Helliwell, R.A.}, title={ Nonlinear pitch angle scattering of energetic electrons by coherent VLF waves in the magnetosphere }, journal={Journal of Geophysical Research}, volume={83}, number={A7}, year={1978}, month={Jul}, pages={3235-53}, abstract={ A computer simulation approach is used to study the nonlinear cyclotron resonant interaction of energetic electrons and coherent VLF waves, with special emphasis on the pitch angle scattering of the particles. Complete equations of motion in an inhomogeneous magnetosphere are used, and the effects of various parameters are studied. Comparison is made with linear theory, and a quantitative and easy-to-use criterion to determine the applicability of linear theory under any given conditions is presented. The full distribution of particles is simulated by test electrons appropriately distributed in energy and pitch angle. By computing the scattering of these test particles and integrating over energy and pitch angle, the precipitated flux is obtained. The results indicate that coherent VLF waves can have a significant effect on the dynamics and lifetimes of energetic electrons trapped in the magnetosphere on magnetic shells illuminated by the waves }, keywords={ atmospheric electron precipitation atmospheric radiation magnetosphere magnetospheric electromagnetic wave propagation whistlers energetic electrons coherent VLF waves magnetosphere computer simulation nonlinear cyclotron resonant interaction pitch angle scattering linear theory applicability criterion 1 to 2 keV electrons precipitated particle flux whistler mode waves wave/particle interactions particle energy integration }, mynotes={UNREAD}, } @ARTICLE{InanJul77, author={Inan, U.S. and Bell, T.F.}, title={ The plasmapause as a VLF wave guide }, journal={Journal of Geophysical Research}, volume={82}, number={19}, year={1977}, month={Jul}, pages={2819-27}, abstract={ The properties of the plasmapause as a VLF wave guide are studied. The guidance that occurs is a form of gradient trapping of VLF wave energy. It is shown that guiding is possible at both the inner and outer edges of the plasmapause and that more efficient guiding occurs as the plasmapause gradients become stronger. In the case of strong gradients, waves coming from a wide latitude range ( approximately 8 degrees ) are focused tightly about the plasmapause field lines, resulting in a wave intensity increase of approximately 3 dB near the magnetic equatorial plane. It is shown that plasmapause-guided waves can be observed on the ground and can echo between hemispheres, precisely as can waves guided in normal whistler ducts. The single distinguishing feature of plasmapause-guided waves is a lowered upper cutoff frequency. The results indicate that the vicinity of the plasmapause represents a natural and readily accessible region of VLF wave guidance and focusing where both passive and active VLF experiments can be studied through ground and in situ satellite measurements }, keywords={ guided electromagnetic wave propagation magnetospheric electromagnetic wave propagation radiowave propagation plasmapause VLF wave guide whistler mode waves }, mynotes={UNREAD}, } @ARTICLE{InanMar77, author={Inan, U.S. and Bell, T.F. and Carpenter, D.L. and Anderson, R.R.}, title={ Explorer 45 and Imp 6 observations in the magnetosphere of injected waves from the Siple Station VLF transmitter }, journal={Journal of Geophysical Research}, volume={82}, number={7}, year={1977}, month={Mar}, pages={1177-87}, abstract={ Reports the first results of a Stanford University-University of Iowa joint experiment in which VLF waves from the Siple Station transmitter in Antarctica are injected into the magnetosphere along the Earth's magnetic field lines and are detected near the magnetic equatorial plane by the Explorer 45 and Imp 6 spacecraft. The purpose of this experiment is to conduct a controlled in situ study of VLF wave-particle interactions, in particular, to determine the propagation characteristics of the injected waves in the magnetosphere, to determine the regions where VLF emissions are produced, and to determine the effective volume of the magnetosphere illuminated by the Siple transmitter }, keywords={ magnetosphere magnetospheric electromagnetic wave propagation radiowave propagation Explorer 45 Imp 6 magnetosphere injected waves Siple Station VLF transmitter Antarctica wave particle interactions }, mynotes={UNREAD}, } @ARTICLE{InanMar77, author={Inan, U.S. and Bell, T.F. and Anderson, R.R.}, title={ Cold plasma diagnostics using satellite measurements of VLF signals from ground transmitters }, journal={Journal of Geophysical Research}, volume={82}, number={7}, year={1977}, month={Mar}, pages={1167-76}, abstract={ A new diagnostic technique to obtain the cold plasma density profile in the magnetosphere is introduced. This method uses satellite measurements of group delay and pulse duration of VLF signals from ground transmitters in conjunction with a detailed ray tracing analysis. An iterative method is involved. This method starts with an approximate density profile, computes the ray paths for that profile, and then compares the properties of the rays that reach the satellite location with the actual satellite measurements. The density profile is then modified to account for any discrepancies between the two results. The same process is repeated with the new profile until one has reasonable agreement between the data and ray tracing results. This method is applied to the case of an Imp 6 pass on June 28, 1973, where strong signals from the Siple VLF transmitter were observed for over 25 min. Good agreement is found between the results of the new technique and the well-known ground whistler techniques of cold plasma diagnostics. The results also serve to illustrate the wide diversity of paths of propagation from ground transmitters to high-altitude satellites during VLF wave injection experiments }, keywords={ atmospheric techniques magnetosphere magnetospheric electromagnetic wave propagation plasma plasma diagnostics satellite measurements VLF signals ground transmitters diagnostic technique cold plasma density profile magnetosphere ray tracing iterative method }, mynotes={UNREAD}, } @CONFERENCE{Bultan97, title={ A four-parameter atomic decomposition of chirplets }, booktitle={1997 IEEE International Conference on Acoustics, Speech, and SignalProcessing (Cat. No.97CB36052)}, volume={}, number={}, year={1997}, month={}, pages={3625-8 vol.5}, abstract={ A new four-parameter atomic decomposition of chirplets is developed for compact representation of signals with chirp components. The four-parameter atom is obtained by scaling the Gaussian function, and then applying the fractional Fourier transform (FRFT), time-shift and frequency-shift operators to the scaled Gaussian. The decomposition is realized by extending the matching pursuit algorithm to four parameters. For this purpose, the four-parameter space is discretized to obtain a dense subset in the Hilbert space. Also, a related time-frequency distribution is developed for clear visualization of the signal components. The decomposition provides a more compact and precise representation of chirp components as compared to the three-parameter ones }, keywords={ chirp modulation Fourier transforms Gaussian processes Hilbert spaces signal representation time-frequency analysis four-parameter atomic decomposition chirplets compact representation chirp components Gaussian function scaling fractional Fourier transform time-shift operators frequency-shift operator matching pursuit algorithm dense subset Hilbert space time-frequency distribution visualization signal component }, mynotes={UNREAD}, } @ARTICLE{BonmassarOct97, author={Bonmassar, G. and Schwartz, E.L.}, title={ Space-variant Fourier analysis: the exponential chirp transform }, journal={IEEE Transactions on Pattern Analysis and Machine Intelligence}, volume={19}, number={10}, year={1997}, month={Oct}, pages={1080-9}, abstract={ Space-variant (or foveating) vision architectures are of importance in both machine and biological vision. In this paper, we focus on a particular space-variant map, the log-polar map, which approximates the primate visual map, and which has been applied in machine vision by a number of investigators during the past two decades. Associated with the log-polar map, we define a new linear integral transform, which we call the exponential chirp transform. This transform provides frequency domain image processing for space-variant image formats, while preserving the major aspects of the shift-invariant properties of the usual Fourier transform. We then show that a log-polar coordinate transform in frequency provides a fast exponential chirp transform. This provides size and rotation, in addition to shift, invariant properties in the transformed space. Finally, we demonstrate the use of the fast exponential chirp algorithm on a database of images in a template matching task, and also demonstrate its uses for spatial filtering }, keywords={ computer vision filtering theory Fourier analysis Fourier transforms frequency-domain analysis image matching real-time systems spatial filters exponential chirp transform space-variant image processing log-polar map machine vision frequency domain analysis Fourier transform template matching spatial filtering rotation scale shift invariance real time systems Fourier analysis }, mynotes={UNREAD}, } @CONFERENCE{Karle97, author={Karle, T. and Reuter, C.}, title={ Time domain analysis of high frequency circuits through measurement-based characterization and parametric techniques }, booktitle={Proceedings of the 1997 Summer Computer Simulation Conference Simulationand Modeling Technology for the Twenty-First Century}, volume={}, number={}, year={1997}, month={}, pages={410-13}, abstract={ The paper addresses a novel time domain technique which characterizes the behaviour of a microwave circuit from a model based parameter estimation process in which the parameters are determined from a set of frequency measurements. The estimation process is robust in the manner in which it can accommodate for noise that is present in the input frequency data. The new parametric technique is evaluated on a microstrip network and the simulated time domain results are validated against: 1) an inverse discrete Fourier transform and 2) a measured inverse Chirp Z transform using a Hewlett Packard 8510C network analyzer }, keywords={ circuit analysis computing digital simulation discrete Fourier transforms microstrip circuits microwave circuits parameter estimation time-domain analysis Z transforms time domain analysis high frequency circuits measurement based characterization parametric techniques time domain technique microwave circuit model based parameter estimation process frequency measurements input frequency data parametric technique microstrip network simulated time domain results inverse discrete Fourier transform measured inverse Chirp Z transform Hewlett Packard 8510C network analyzer }, mynotes={UNREAD}, } @CONFERENCE{Salous97, title={ Auto-regressive estimation of spectral width of chirp sounder signals }, booktitle={Seventh International Conference on HF Radio Systems and Techniques (Conf.Publ. No.441)}, volume={}, number={}, year={1997}, month={}, pages={115-19}, abstract={ A major limitation of HF chirp sounders is the use of fast Fourier transform (FFT) analysis to resolve the different multipath components. To reduce the effects of spectral leakage associated with the FFT, the signal is usually weighted by a suitable window prior to spectral analysis. The choice of window function and its effects on the measured width of the dispersed chirp pulse has been previously studied. It was found that the window with the narrowest main lobe gave the best resolution in the least dispersive part of the ionograms whereas the window with the highest attenuation of the edges and hence the widest main lobe had the best resolution in the most dispersive parts. Since the mainlobe of the window is the narrowest width that can be measured non-dispersed pulses will be masked by it. Hence, a spectral estimation technique which is capable of avoiding the limitations of FFT analysis is desirable. Modern spectral estimation techniques such as autoregressive (AR) modelling extend the signal outside the observation interval rather than windowing it to zero as in the FFT. The implied extrapolation results in a higher resolution than is obtained from the FFT which is limited to the inverse of the observation interval. The enhancement of resolution with AR analysis depends on the signal to noise ratio (SNR). The HF spectrum is highly congested. Hence, techniques such as filtering and interference reduction to improve the SNR prior to AR analysis would be required. This paper discusses the analysis stages for both FFT analysis and AR analysis. The results of applying both techniques to ionospheric data obtained over a short skywave link in the UK are presented }, keywords={ autoregressive processes delays fast Fourier transforms FM radar geophysical signal processing ionospheric techniques multipath channels radar signal processing remote sensing by radar signal resolution spectral analysis auto-regressive estimation spectral width chirp sounder signals multipath components spectral leakage window function main lobe spectral estimation technique extrapolation resolution signal to noise ratio HF spectrum FFT analysis AR analysis ionospheric data short skywave link UK United Kingdom }, mynotes={UNREAD}, } @ARTICLE{IkramApr97, author={Ikram, M.Z. and Abed-Meraim, K. and Hua, Y.}, title={ Fast quadratic phase transform for estimating the parameters of multicomponent chirp signals }, journal={Digital Signal Processing}, volume={7}, number={2}, year={1997}, month={Apr}, pages={127-35}, abstract={ We present a technique based on the quadratic phase transform (QPT) for joint phase parameter estimation of multicomponent chirp signals. The QPT has the ability to analyze chirp signals in the same way as the Fourier transform analyzes sinusoidal signals. In view of its practical implementation, a discrete version of the QPT, called the discrete quadratic phase transform (DQPT), is introduced. A novel fast computational procedure of the DQPT is developed. Explicit expressions for the arithmetic operation count are derived. Simulation results are presented to illustrate the usefulness of the DQPT }, keywords={ chirp modulation phase estimation signal processing transforms multicomponent chirp signals phase parameter estimation discrete quadratic phase transform arithmetic operation count simulation results }, mynotes={UNREAD}, } @CONFERENCE{Toshio96, title={ A gammachirp' function as an optimal auditory filter with the Mellin transform }, booktitle={1996 IEEE International Conference on Acoustics, Speech, and SignalProcessing Conference Proceedings (Cat. No.96CH35903)}, volume={}, number={}, year={1996}, month={}, pages={981-4 vol. 2}, abstract={ A gammachirp' function has been derived as an optimal auditory filter function in terms of minimal uncertainty in a joint time and modified-scale representation if the scale transform defined by Cohen (1989) is used in the auditory system. The gammatone function, which is widely used as the impulse response of a linear auditory filter, is a first-order approximation of the gammachirp' function consisting of a chirp carrier with an envelope that is a gamma distribution function. The optimality of the gammachirp' function is argued for the general Mellin transform since Cohen's scale transform is a specific example of the Mellin transform. A sample speech signal is analyzed to demonstrate the properties of a joint time and scale distribution derived with a short-time Mellin transform in comparison with a short-time Fourier spectrum }, keywords={ band-pass filters filtering theory gamma distribution hearing signal representation speech processing transforms transient response gammachirp function optimal auditory filter minimal uncertainty modified-scale representation time representation Cohen scale transform auditory system gammatone function impulse response linear auditory filter first-order approximation chirp carrier envelope gamma distribution function sample speech signal speech signal analysis scale distribution time distribution short-time Mellin transform short-time Fourier spectrum }, mynotes={UNREAD}, } @ARTICLE{Wang96, author={Wang, H.-J. and Yang, T.-C. and Jay Kuo, C.-C.}, title={ A new time-frequency approach for weak chirp signal detection }, journal={Proc. SPIE - Int. Soc. Opt. Eng. (USA), Proceedings of the SPIE - TheInternational Society for Optical Engineering}, volume={2762}, number={}, year={1996}, month={}, pages={270-80}, abstract={ Several methods have been proposed to detect chirp signals buried in white noise, including wavelet shrinkage and matching pursuits. However, most of these methods perform poorly when the signal-to-noise ratio (SNR) becomes very low (e.g. lower than 0 dB). In this work, we present a new time-frequency technique using the multi-window Fourier transform (MWFT) and local maximum indexing. The new method detects the location and frequency range of a chirp signal with SNR up to -6dB }, keywords={ chirp modulation signal detection time-frequency analysis white noise time-frequency approach weak chirp signal detection white noise signal-to-noise ratio multi-window Fourier transform local maximum indexing }, mynotes={UNREAD}, } @ARTICLE{MannNov95, author={Mann, S. and Haykin, S.}, title={ The chirplet transform: physical considerations }, journal={IEEE Transactions on Signal Processing}, volume={43}, number={11}, year={1995}, month={Nov}, pages={2745-61}, abstract={ We consider a multidimensional parameter space formed by inner products of a parameterizable family of chirp functions with a signal under analysis. We propose the use of quadratic chirp functions (which we will call q-chirps for short), giving rise to a parameter space that includes both the time-frequency plane and the time-scale plane as 2-D subspaces. The parameter space contains a "time-frequency-scale volume" and thus encompasses both the short-time Fourier transform (as a slice along the time and frequency axes) and the wavelet transform (as a slice along the time and scale axes). In addition to time, frequency, and scale, there are two other coordinate axes within this transform space: shear in time (obtained through convolution with a q-chirp) and shear in frequency (obtained through multiplication by a q-chirp). Signals in this multidimensional space can be obtained by a new transform, which we call the "q-chirplet transform" or simply the "chirplet transform". The proposed chirplets are generalizations of wavelets related to each other by 2-D affine coordinate transformations (translations, dilations, rotations, and shears) in the time-frequency plane, as opposed to wavelets, which are related to each other by 1-D affine coordinate transformations (translations and dilations) in the time domain only }, keywords={ chirp modulation convolution Fourier transforms signal processing signal representation time-frequency analysis wavelet transforms chirplet transform multidimensional parameter space quadratic chirp functions signal analysis physical considerations q-chirps time-frequency plane time-scale plane 2-D subspaces time-frequency-scale volume short-time Fourier transform wavelet transform shear in time shear in frequency convolution multiplication 2-D affine coordinate transformations translations dilations rotations shears signal processing }, mynotes={UNREAD}, } @CONFERENCE{Santhanam95, author={Santhanam, B. and McClellan, J.H.}, title={ The DRFT-a rotation in time-frequency space }, booktitle={1995 International Conference on Acoustics, Speech, and Signal Processing.Conference Proceedings (Cat. No.95CH35732)}, volume={}, number={}, year={1995}, month={}, pages={921-4 vol.2}, abstract={ The continuous-time angular Fourier transformation (AFT) represents a rotation in continuous time-frequency space and also serves as an orthonormal signal representation for chirp signals. We present a discrete version of the AFT (DRFT) that represents a rotation in discrete time-frequency space and some properties of the transform that support its interpretation as a rotation. The transform is a generalization of the DFT. The eigenvalue structure of the DFT is then exploited to develop an efficient algorithm for the computation of this transform }, keywords={ discrete Fourier transforms eigenvalues and eigenfunctions signal representation spectral analysis time-frequency analysis discrete rotational Fourier transform continuous-time angular Fourier transformation continuous time-frequency space orthonormal signal representation chirp signals rotation DFT eigenvalue structure algorithm }, mynotes={UNREAD}, } @ARTICLE{Filipiak93, author={Filipiak, J. and Kawalec, A.}, title={ Broadband dispersive delay line for compressive receiver on quartz substrate }, journal={Opto-Electronics Review}, volume={}, number={}, year={1993}, month={}, pages={135-6}, abstract={ Surface acoustic wave chirp transformation is an analog technique for making the Fourier transform of signals in real time. In multiplication-convolution configuration, the use of chirp filters with time-bandwidth product TB provides the signal spectrum with maximum number of points equal to TB/4. Dispersive delay liners (DDL) of large TB are discussed. Results of theoretical and experimental investigations of DDL with 100% passband built on the quartz substrate, are presented }, keywords={ acoustic signal processing band-pass filters quartz surface acoustic wave filters ultrasonic delay lines ultrasonic transducers broadband dispersive delay line compressive receiver quartz substrate surface acoustic wave chirp transformation analog technique Fourier transform real time multiplication-convolution configuration chirp filters time-bandwidth product signal spectrum dispersive delay liner passband 70 MHz SiO/sub 2/ }, mynotes={UNREAD}, } @ARTICLE{LawtonJul92, title={ Multidimensional chirp algorithms for computing Fourier transforms }, journal={IEEE Transactions on Image Processing}, volume={1}, number={3}, year={1992}, month={Jul}, pages={429-31}, abstract={ Continuous versions of the multidimensional chirp algorithms compute the function G(y)=F(My), where F(y) is the Fourier transform of a function f(x) of a vector variable x and M is an invertible matrix. Discrete versions of the algorithms compute values of F over the lattice L/sub 2/=ML/sub 1/ from values of f over a lattice L/sub 1/, where L/sub 2/ need not contain the lattice reciprocal to L/sub 1/. If M is symmetric, the algorithms are multidimensional versions of the Bluestein chirp algorithm, which employs two pointwise multiplication operations (PMOs) and one convolution operation (CO). The discrete version may be efficiently implemented using fast algorithms to compute the convolutions. If M is not symmetric, three modifications are required. First, the Fourier transform is factored as the product of two Fresnel transforms. Second, the matrix M is factored as M=AB, where A and B are symmetric matrices. Third, the Fresnel transforms are modified by the matrices A and B and each modified transform is factored into a product of two PMOs and one CO }, keywords={ fast Fourier transforms matrix algebra vectors discrete Fourier transform computation DFT multidimensional chirp algorithms invertible matrix M Bluestein chirp algorithm pointwise multiplication operations convolution operation fast algorithms Fresnel transforms symmetric matrices }, mynotes={UNREAD}, } @ARTICLE{JonesDec90, author={Jones, D.L. and Parks, T.W.}, title={ A high resolution data-adaptive time-frequency representation }, journal={IEEE Transactions on Acoustics, Speech and Signal Processing}, volume={38}, number={12}, year={1990}, month={Dec}, pages={2127-35}, abstract={ A data-adaptive time-frequency representation is developed that overcomes some limitations of the short-time Fourier transform, while avoiding the cross-terms that make the Wigner distribution and other bilinear representations difficult to interpret. The adaptive time-frequency representations uses Gaussian basis functions but varies their time width and chirp rate with time and frequency to achieve high signal concentration everywhere. A measure of local signal concentration allows fully automated determination of the optimal basis parameters. The adaptive method is computationally expensive, but may provide much better performance than any currently known technique }, keywords={ signal processing spectral analysis signal processing frequency analysis data-adaptive time-frequency representation short-time Fourier transform Gaussian basis functions time width chirp rate local signal concentration optimal basis parameters }, mynotes={UNREAD}, } @ARTICLE{JonesApr91, author={Jones, D.L. and Baraniuk, R.G.}, title={ Efficient approximation of continuous wavelet transforms }, journal={Electronics Letters}, volume={27}, number={9}, year={1991}, month={Apr}, pages={748-50}, abstract={ An efficient algorithm is developed for computing the continuous wavelet transform or wideband ambiguity function on a grid whose samples are spaced uniformly in time but placed arbitrarily in scale. The method is based on the chirp z transform and requires the same order of computation as constant-bandwidth analysis techniques, such as the short-time Fourier transform and narrowband ambiguity function }, keywords={ computational complexity signal processing transforms efficient algorithm continuous wavelet transform wideband ambiguity function chirp z transform order of computation }, mynotes={UNREAD}, } @ARTICLE{ChallisJan91, author={Challis, R.E. and Kitney, R.I.}, title={ Biomedical signal processing. II. The frequency transforms and their inter-relationships }, journal={Medical & Biological Engineering & Computing}, volume={29}, number={1}, year={1991}, month={Jan}, pages={1-17}, abstract={ For pt.I see ibid., vol.28, p.509 (1990). This tutorial paper on biomedical signal processing concerns the relationships between commonly used frequency transforms. It begins with the Fourier series and Fourier transform for continuous time signals and extends these concepts for aperiodic discrete time data and then periodic discrete time data. The Laplace transform is discussed as an extension of the Fourier transform. The Z-transform is introduced and the ideas behind the chirp-Z transform are described. The equivalence between the time and frequency domains is described in terms of Parseval's theorem and the theory of convolution. The use of the FFT for fast convolution and fast correlation is described for both short recordings and long recordings that must be processed in sections }, keywords={ biomedical measurement Fourier transforms Laplace transforms reviews signal processing Z transforms digital signal processing frequency transforms biomedical signal processing Fourier series Fourier transform continuous time signals aperiodic discrete time data periodic discrete time data Laplace transform Z-transform chirp-Z transform Parseval's theorem FFT fast convolution fast correlation }, mynotes={UNREAD}, } @ARTICLE{WangApr90, title={ The segmented chirp Z-transform and its application in spectrum analysis }, journal={IEEE Transactions on Instrumentation and Measurement}, volume={39}, number={2}, year={1990}, month={Apr}, pages={318-23}, abstract={ The chirp Z-transform (CZT) algorithm is known to be more flexible than the fast Fourier transform in calculating the frequency spectrum. However, its mathematical implementation is complex, and additional memory space is required. A modified CZT algorithm called the segmented chirp Z transform (SCZT) is introduced. SCZT has the ability to handle a very large amount of input data with very limited memory space and to limit its calculation to a portion of the frequency spectrum of interest with greatly increased dynamic range and frequency resolution }, keywords={ computerised signal processing spectral analysis Z transforms segmented algorithm instrumentation segmented chirp Z-transform spectrum analysis frequency spectrum }, mynotes={UNREAD}, } @CONFERENCE{Kobayashi88, title={ A fast method of chirp signal analysis }, booktitle={Signal Processing IV: Theories and Applications. Proceedings of EUSIPCO-88.Fourth European Signal Processing Conference}, volume={}, number={}, year={1988}, month={}, pages={383-6 vol.1}, abstract={ As a vehicle for time-varying signals analysis, a method is presented to determine the average frequency and chirp rate of a signal with an order of computation O(Nlog/sub 2/N+N/sup 2/), as contrasted to O(N/sup 2/log/sub 2/N) of the traditional method. The derived chirp-rate parameter could be used for data-adaptive windows for high-resolution Fourier transforms }, keywords={ fast Fourier transforms spectral analysis FFT spectral analysis chirp signal analysis time-varying signals frequency chirp rate order of computation data-adaptive windows high-resolution Fourier transforms }, mynotes={UNREAD}, } @ARTICLE{McIverMay89, author={McIver, R.T. and Jr., Baykut and G. and Hunter, R.L.}, title={ Theory of impulse excitation for Fourier transform mass spectrometry }, journal={International Journal of Mass Spectrometry and Ion Processes}, volume={89}, number={2-3}, year={1989}, month={May}, pages={343-58}, abstract={ Most Fourier transform mass spectrometer utilize a rapid radio frequency sweep, or 'chirp', to accelerate and detect ions. Impulse excitation is different because the ions are accelerated by a very short, high voltage DC pulse. In this paper, an analytical theory of impulse excitation is presented. Ion trajectories are plotted to illustrate the effects of pulse width, pulse height and 'risetime' and 'falltime' of the pulse on the ion motion. To minimize mass discrimination, the risetime of the impulse signal must be very fast (50-100 ns) and the pulse width must be much shorter than the period of the cyclotron orbit of an ion }, keywords={ Fourier transform spectroscopy mass spectroscopy ion acceleration ion detection ion trajectories impulse excitation Fourier transform mass spectrometry Fourier transform mass spectrometer radio frequency sweep DC pulse pulse width pulse height falltime ion motion mass discrimination risetime impulse signal cyclotron orbit }, mynotes={UNREAD}, } @CONFERENCE{Gibbins89, title={ Atmospheric effects on the propagation of very short pulses at millimetric wavelengths }, booktitle={Sixth International Conference on Antennas and Propagation (ICAP 89) (Conf.Publ. No.301)}, volume={}, number={}, year={1989}, month={}, pages={432-6 vol.2}, abstract={ An alternative approach to the solution of the Fourier integral in closed form was adopted by Terina (1967) for reflections from the ionosphere of pulsed HF (3-6 MHz) transmissions. This technique, appropriate to any line shape, assumes that the atmospheric channel transfer function can be approximated by a truncated Taylor series of frequency; its validity thus relies on the presumption that high-order terms can be neglected. Although this may not be strictly valid at frequencies very close to resonant absorption lines, the treatment allows an examination of a variety of phenomena arising from the dispersive nature of the atmosphere, such as the imposition of frequency modulation (chirp) on the carrier frequency within the pulse and the corresponding changes in the spectrum which arise through the frequency-dependent group velocity. This analysis has been considered briefly for line-of-sight transmissions near 55 GHz by Medeiros Filho et al (1983). The paper extends this to investigate absorptive and dispersive effects on pulses at carrier frequencies between 10 and 200 GHz, for pulse widths between 2 ns and 0.1 ns, for line-of-sight pathlengths from 1 to 50 km, and along Earth-space paths }, keywords={ atmospheric electromagnetic wave propagation electromagnetic pulse radiowave propagation very short pulses propagation SHF EHF millimetric wavelengths reflections ionosphere atmospheric channel transfer function truncated Taylor series frequency modulation chirp carrier frequency group velocity line-of-sight transmissions dispersive effects pulse widths Earth-space paths 3 to 6 MHz 10 to 200 GHz 0.1 to 10 ns 1 to 50 km }, mynotes={UNREAD}, } @ARTICLE{PooleNov85, title={ Advanced sounding. I. The FMCW alternative }, journal={Radio Science}, volume={20}, number={6}, year={1985}, month={Nov}, pages={1609-16}, abstract={ HF radar employing linear frequency-modulated continuous wave or 'chirp' modulation provides an alternative to the more conventional pulsed amplitude modulation technique in advanced ionosphere sounding. An analysis is presented which shows that the phases of the discrete Fourier components of the receiver output can be used in the same fashion as the phases of pulsed, fixed frequency ionospheric echoes to evaluate the standard digital parameters, including group path by the method of stationary phase. This can be used to overcome the group path/Doppler velocity ambiguity of linear frequency modulation. A description is given of a sounding structure from which unambiguous group range, angle of arrival, O/X mode, and Doppler velocity can be evaluated. A simple error analysis is also given }, keywords={ ionospheric electromagnetic wave propagation ionospheric measuring apparatus ionospheric techniques radar systems radiowave propagation chirp modulation polarization mode HF radar linear frequency-modulated continuous wave advanced ionosphere sounding Fourier components receiver output group path stationary phase Doppler velocity group range angle of arrival error analysis }, mynotes={UNREAD}, } @ARTICLE{ZakareviciusMar81, title={ Chirp waveforms and signal processing }, journal={Journal of Electrical and Electronics Engineering, Australia}, volume={1}, number={1}, year={1981}, month={Mar}, pages={93-8}, abstract={ Chirp waveforms are waveforms with a carrier frequency which varies linearly with time. They can be employed in various signal processing operations, the most important of which is Fourier Transformation. Other applications include signal compression/dilation, time reversal and electronically variable time delay, all of which can be achieved with no signal distortion. This paper takes a tutorial approach to explain the role of chirp waveforms in these signal processing operations and their practical applications. Whenever possible, the underlying physical principles are emphasised }, keywords={ Fourier analysis Fourier transforms signal processing signal processing Fourier Transformation chirp waveforms practical applications physical principles }, mynotes={UNREAD}, } @ARTICLE{QuatieriDec78, title={ Short-time spectral analysis with the conventional and sliding CZT }, journal={IEEE Transactions on Acoustics, Speech and Signal Processing}, volume={ASSP-26}, number={6}, year={1978}, month={Dec}, pages={561-6}, abstract={ Two sequential short-time spectral analysis techniques, amenable to nonrecursive filter implementation, are the conventional chirp-z-transform (CZT) realization of the discrete Fourier transform and the sliding CZT realization of the discrete sliding Fourier transform. This paper presents a comparative study of frame rate limitations, windowing, time and frequency resolution, spectral correlation, complexity, and inverse structures for these methods, with particular emphasis on the recently proposed sliding transform. The sliding transform and its CZT realization are viewed as skewed output samples of a filter bank, an approach which aids in understanding the relationship between the conventional and sliding schemes. Numerous forward and inverse CZT formulations are presented to improve resolution, frame rates, and compactness }, keywords={ Fourier transforms spectral analysis Z transforms discrete Fourier transform CZT realization discrete sliding Fourier transform frame rate limitations windowing frequency resolution spectral correlation complexity inverse structures signal processing short time spectral analysis chirp z-transform }, mynotes={UNREAD}, } @ARTICLE{ZakareviciusMay77, title={ Signal processing with fast chirp waveforms }, journal={Electronics Letters}, volume={13}, number={10}, year={1977}, month={May}, pages={296-7}, abstract={ The analysis shows that the implementation with chirp waveforms of the operations of time compression and variable delay of signals can be significantly simplified if fast rates of chirp are used. A related simplification for Fourier transformation is also presented }, keywords={ signal processing fast chirp waveforms time compression variable delay Fourier transformation signal processing }, mynotes={UNREAD}, } @ARTICLE{BlochJul73, title={ Introduction to chirp concepts with a cheap chirp radar }, journal={American Journal of Physics}, volume={41}, number={7}, year={1973}, month={Jul}, pages={857-64}, abstract={ The elements of pulse compression of a chirp in a dispersive delay are reviewed and chirp and pulse modes are contrasted. A simple microwave Doppler-shift apparatus is modified into a chirp system to permit distance measurement in a laboratory experiment that is rich in fundamental concepts of physical parameters which are related by the Fourier transform, and which involve the convergence of ideas from several disciplines }, keywords={ demonstrations distance measurement radar chirp concepts chirp radar pulse compression pulse modes distance measurement Fourier transform microwave Doppler shift apparatus }, mynotes={UNREAD}, } @ARTICLE{RabinerMay69, author={Rabiner, L.R. and Schafer, R.W. and Rader, C.M.}, title={ The chirp z-transform algorithm and its application }, journal={Bell System Technical Journal}, volume={48}, number={5}, year={1969}, month={May}, pages={1249-92}, abstract={ A computational algorithm is discussed for numerically evaluating the z-transform of a sequence of N samples. This algorithm has been named the chirp z-transform algorithm. Using this algorithm one can efficiently evaluate the z-transform at M points in the z-plane which lie on circular or spiral contours beginning at any arbitrary point in the z-plane. The angular spacing of the points is an arbitrary constant; M and N are arbitrary integers. The algorithm is based on the fact that the values of the z-transform on a circular or spiral contour can be expressed as a discrete convolution. Thus one can use well-known high-speed convolution techniques to evaluate the transform efficiently. For M and N moderately large, the computation time is roughly proportional to (N+M) log/sub 2/ (N+M) as opposed to being proportional to N.M for direct evaluation of the z-transform at M points. Applications discussed include: enhancement of poles in spectral analysis, high resolution narrow-band frequency analysis, interpolation of band-limited waveforms, and the conversion of a base 2 fast Fourier transform program into an arbitrary radix fast Fourier transform program }, keywords={ numerical analysis subroutines Z transforms }, mynotes={UNREAD}, } @ARTICLE{Hamed97, author={Hamed, Z.F. and Flores, B.C.}, title={ Wideband spectral reconstruction via short-time modified chirp z-transform processing }, journal={Proc. SPIE - Int. Soc. Opt. Eng. (USA), Proceedings of the SPIE - TheInternational Society for Optical Engineering}, volume={3161}, number={}, year={1997}, month={}, pages={113-24}, abstract={ The chirp z-transform is adapted for the spectral reconstruction of a wideband signal. Here, spectral reconstruction is based on the coherent and sequential processing of non-overlapping short-time segments. This approach eases hardware implementation in the presence of limited memory allocation and can provide savings in computational effort. In addition, it offers the flexibility of focusing the reconstruction of the spectrum on a narrow spectral band of interest }, keywords={ coherence discrete Fourier transforms signal reconstruction spectral analysis Z transforms wideband spectral reconstruction short-time modified chirp z-transform processing wideband signal sequential processing coherent processing nonoverlapping short-time segments hardware implementation limited memory allocation computational effort savings narrow spectral band FFT DFT }, mynotes={UNREAD}, } @CONFERENCE{Bultan97, title={ A four-parameter atomic decomposition of chirplets }, booktitle={1997 IEEE International Conference on Acoustics, Speech, and SignalProcessing (Cat. No.97CB36052)}, volume={}, number={}, year={1997}, month={}, pages={3625-8 vol.5}, abstract={ A new four-parameter atomic decomposition of chirplets is developed for compact representation of signals with chirp components. The four-parameter atom is obtained by scaling the Gaussian function, and then applying the fractional Fourier transform (FRFT), time-shift and frequency-shift operators to the scaled Gaussian. The decomposition is realized by extending the matching pursuit algorithm to four parameters. For this purpose, the four-parameter space is discretized to obtain a dense subset in the Hilbert space. Also, a related time-frequency distribution is developed for clear visualization of the signal components. The decomposition provides a more compact and precise representation of chirp components as compared to the three-parameter ones }, keywords={ chirp modulation Fourier transforms Gaussian processes Hilbert spaces signal representation time-frequency analysis four-parameter atomic decomposition chirplets compact representation chirp components Gaussian function scaling fractional Fourier transform time-shift operators frequency-shift operator matching pursuit algorithm dense subset Hilbert space time-frequency distribution visualization signal component }, mynotes={UNREAD}, } @ARTICLE{BonmassarOct97, author={Bonmassar, G. and Schwartz, E.L.}, title={ Space-variant Fourier analysis: the exponential chirp transform }, journal={IEEE Transactions on Pattern Analysis and Machine Intelligence}, volume={19}, number={10}, year={1997}, month={Oct}, pages={1080-9}, abstract={ Space-variant (or foveating) vision architectures are of importance in both machine and biological vision. In this paper, we focus on a particular space-variant map, the log-polar map, which approximates the primate visual map, and which has been applied in machine vision by a number of investigators during the past two decades. Associated with the log-polar map, we define a new linear integral transform, which we call the exponential chirp transform. This transform provides frequency domain image processing for space-variant image formats, while preserving the major aspects of the shift-invariant properties of the usual Fourier transform. We then show that a log-polar coordinate transform in frequency provides a fast exponential chirp transform. This provides size and rotation, in addition to shift, invariant properties in the transformed space. Finally, we demonstrate the use of the fast exponential chirp algorithm on a database of images in a template matching task, and also demonstrate its uses for spatial filtering }, keywords={ computer vision filtering theory Fourier analysis Fourier transforms frequency-domain analysis image matching real-time systems spatial filters exponential chirp transform space-variant image processing log-polar map machine vision frequency domain analysis Fourier transform template matching spatial filtering rotation scale shift invariance real time systems Fourier analysis }, mynotes={UNREAD}, } @CONFERENCE{Karle97, author={Karle, T. and Reuter, C.}, title={ Time domain analysis of high frequency circuits through measurement-based characterization and parametric techniques }, booktitle={Proceedings of the 1997 Summer Computer Simulation Conference Simulationand Modeling Technology for the Twenty-First Century}, volume={}, number={}, year={1997}, month={}, pages={410-13}, abstract={ The paper addresses a novel time domain technique which characterizes the behaviour of a microwave circuit from a model based parameter estimation process in which the parameters are determined from a set of frequency measurements. The estimation process is robust in the manner in which it can accommodate for noise that is present in the input frequency data. The new parametric technique is evaluated on a microstrip network and the simulated time domain results are validated against: 1) an inverse discrete Fourier transform and 2) a measured inverse Chirp Z transform using a Hewlett Packard 8510C network analyzer }, keywords={ circuit analysis computing digital simulation discrete Fourier transforms microstrip circuits microwave circuits parameter estimation time-domain analysis Z transforms time domain analysis high frequency circuits measurement based characterization parametric techniques time domain technique microwave circuit model based parameter estimation process frequency measurements input frequency data parametric technique microstrip network simulated time domain results inverse discrete Fourier transform measured inverse Chirp Z transform Hewlett Packard 8510C network analyzer }, mynotes={UNREAD}, } @CONFERENCE{Salous97, title={ Auto-regressive estimation of spectral width of chirp sounder signals }, booktitle={Seventh International Conference on HF Radio Systems and Techniques (Conf.Publ. No.441)}, volume={}, number={}, year={1997}, month={}, pages={115-19}, abstract={ A major limitation of HF chirp sounders is the use of fast Fourier transform (FFT) analysis to resolve the different multipath components. To reduce the effects of spectral leakage associated with the FFT, the signal is usually weighted by a suitable window prior to spectral analysis. The choice of window function and its effects on the measured width of the dispersed chirp pulse has been previously studied. It was found that the window with the narrowest main lobe gave the best resolution in the least dispersive part of the ionograms whereas the window with the highest attenuation of the edges and hence the widest main lobe had the best resolution in the most dispersive parts. Since the mainlobe of the window is the narrowest width that can be measured non-dispersed pulses will be masked by it. Hence, a spectral estimation technique which is capable of avoiding the limitations of FFT analysis is desirable. Modern spectral estimation techniques such as autoregressive (AR) modelling extend the signal outside the observation interval rather than windowing it to zero as in the FFT. The implied extrapolation results in a higher resolution than is obtained from the FFT which is limited to the inverse of the observation interval. The enhancement of resolution with AR analysis depends on the signal to noise ratio (SNR). The HF spectrum is highly congested. Hence, techniques such as filtering and interference reduction to improve the SNR prior to AR analysis would be required. This paper discusses the analysis stages for both FFT analysis and AR analysis. The results of applying both techniques to ionospheric data obtained over a short skywave link in the UK are presented }, keywords={ autoregressive processes delays fast Fourier transforms FM radar geophysical signal processing ionospheric techniques multipath channels radar signal processing remote sensing by radar signal resolution spectral analysis auto-regressive estimation spectral width chirp sounder signals multipath components spectral leakage window function main lobe spectral estimation technique extrapolation resolution signal to noise ratio HF spectrum FFT analysis AR analysis ionospheric data short skywave link UK United Kingdom }, mynotes={UNREAD}, } @ARTICLE{IkramApr97, author={Ikram, M.Z. and Abed-Meraim, K. and Hua, Y.}, title={ Fast quadratic phase transform for estimating the parameters of multicomponent chirp signals }, journal={Digital Signal Processing}, volume={7}, number={2}, year={1997}, month={Apr}, pages={127-35}, abstract={ We present a technique based on the quadratic phase transform (QPT) for joint phase parameter estimation of multicomponent chirp signals. The QPT has the ability to analyze chirp signals in the same way as the Fourier transform analyzes sinusoidal signals. In view of its practical implementation, a discrete version of the QPT, called the discrete quadratic phase transform (DQPT), is introduced. A novel fast computational procedure of the DQPT is developed. Explicit expressions for the arithmetic operation count are derived. Simulation results are presented to illustrate the usefulness of the DQPT }, keywords={ chirp modulation phase estimation signal processing transforms multicomponent chirp signals phase parameter estimation discrete quadratic phase transform arithmetic operation count simulation results }, mynotes={UNREAD}, } @CONFERENCE{Toshio96, title={ A gammachirp' function as an optimal auditory filter with the Mellin transform }, booktitle={1996 IEEE International Conference on Acoustics, Speech, and SignalProcessing Conference Proceedings (Cat. No.96CH35903)}, volume={}, number={}, year={1996}, month={}, pages={981-4 vol. 2}, abstract={ A gammachirp' function has been derived as an optimal auditory filter function in terms of minimal uncertainty in a joint time and modified-scale representation if the scale transform defined by Cohen (1989) is used in the auditory system. The gammatone function, which is widely used as the impulse response of a linear auditory filter, is a first-order approximation of the gammachirp' function consisting of a chirp carrier with an envelope that is a gamma distribution function. The optimality of the gammachirp' function is argued for the general Mellin transform since Cohen's scale transform is a specific example of the Mellin transform. A sample speech signal is analyzed to demonstrate the properties of a joint time and scale distribution derived with a short-time Mellin transform in comparison with a short-time Fourier spectrum }, keywords={ band-pass filters filtering theory gamma distribution hearing signal representation speech processing transforms transient response gammachirp function optimal auditory filter minimal uncertainty modified-scale representation time representation Cohen scale transform auditory system gammatone function impulse response linear auditory filter first-order approximation chirp carrier envelope gamma distribution function sample speech signal speech signal analysis scale distribution time distribution short-time Mellin transform short-time Fourier spectrum }, mynotes={UNREAD}, } @ARTICLE{Wang96, author={Wang, H.-J. and Yang, T.-C. and Jay Kuo, C.-C.}, title={ A new time-frequency approach for weak chirp signal detection }, journal={Proc. SPIE - Int. Soc. Opt. Eng. (USA), Proceedings of the SPIE - TheInternational Society for Optical Engineering}, volume={2762}, number={}, year={1996}, month={}, pages={270-80}, abstract={ Several methods have been proposed to detect chirp signals buried in white noise, including wavelet shrinkage and matching pursuits. However, most of these methods perform poorly when the signal-to-noise ratio (SNR) becomes very low (e.g. lower than 0 dB). In this work, we present a new time-frequency technique using the multi-window Fourier transform (MWFT) and local maximum indexing. The new method detects the location and frequency range of a chirp signal with SNR up to -6dB }, keywords={ chirp modulation signal detection time-frequency analysis white noise time-frequency approach weak chirp signal detection white noise signal-to-noise ratio multi-window Fourier transform local maximum indexing }, mynotes={UNREAD}, } @ARTICLE{MannNov95, author={Mann, S. and Haykin, S.}, title={ The chirplet transform: physical considerations }, journal={IEEE Transactions on Signal Processing}, volume={43}, number={11}, year={1995}, month={Nov}, pages={2745-61}, abstract={ We consider a multidimensional parameter space formed by inner products of a parameterizable family of chirp functions with a signal under analysis. We propose the use of quadratic chirp functions (which we will call q-chirps for short), giving rise to a parameter space that includes both the time-frequency plane and the time-scale plane as 2-D subspaces. The parameter space contains a "time-frequency-scale volume" and thus encompasses both the short-time Fourier transform (as a slice along the time and frequency axes) and the wavelet transform (as a slice along the time and scale axes). In addition to time, frequency, and scale, there are two other coordinate axes within this transform space: shear in time (obtained through convolution with a q-chirp) and shear in frequency (obtained through multiplication by a q-chirp). Signals in this multidimensional space can be obtained by a new transform, which we call the "q-chirplet transform" or simply the "chirplet transform". The proposed chirplets are generalizations of wavelets related to each other by 2-D affine coordinate transformations (translations, dilations, rotations, and shears) in the time-frequency plane, as opposed to wavelets, which are related to each other by 1-D affine coordinate transformations (translations and dilations) in the time domain only }, keywords={ chirp modulation convolution Fourier transforms signal processing signal representation time-frequency analysis wavelet transforms chirplet transform multidimensional parameter space quadratic chirp functions signal analysis physical considerations q-chirps time-frequency plane time-scale plane 2-D subspaces time-frequency-scale volume short-time Fourier transform wavelet transform shear in time shear in frequency convolution multiplication 2-D affine coordinate transformations translations dilations rotations shears signal processing }, mynotes={UNREAD}, } @CONFERENCE{Santhanam95, author={Santhanam, B. and McClellan, J.H.}, title={ The DRFT-a rotation in time-frequency space }, booktitle={1995 International Conference on Acoustics, Speech, and Signal Processing.Conference Proceedings (Cat. No.95CH35732)}, volume={}, number={}, year={1995}, month={}, pages={921-4 vol.2}, abstract={ The continuous-time angular Fourier transformation (AFT) represents a rotation in continuous time-frequency space and also serves as an orthonormal signal representation for chirp signals. We present a discrete version of the AFT (DRFT) that represents a rotation in discrete time-frequency space and some properties of the transform that support its interpretation as a rotation. The transform is a generalization of the DFT. The eigenvalue structure of the DFT is then exploited to develop an efficient algorithm for the computation of this transform }, keywords={ discrete Fourier transforms eigenvalues and eigenfunctions signal representation spectral analysis time-frequency analysis discrete rotational Fourier transform continuous-time angular Fourier transformation continuous time-frequency space orthonormal signal representation chirp signals rotation DFT eigenvalue structure algorithm }, mynotes={UNREAD}, } @ARTICLE{Filipiak93, author={Filipiak, J. and Kawalec, A.}, title={ Broadband dispersive delay line for compressive receiver on quartz substrate }, journal={Opto-Electronics Review}, volume={}, number={}, year={1993}, month={}, pages={135-6}, abstract={ Surface acoustic wave chirp transformation is an analog technique for making the Fourier transform of signals in real time. In multiplication-convolution configuration, the use of chirp filters with time-bandwidth product TB provides the signal spectrum with maximum number of points equal to TB/4. Dispersive delay liners (DDL) of large TB are discussed. Results of theoretical and experimental investigations of DDL with 100% passband built on the quartz substrate, are presented }, keywords={ acoustic signal processing band-pass filters quartz surface acoustic wave filters ultrasonic delay lines ultrasonic transducers broadband dispersive delay line compressive receiver quartz substrate surface acoustic wave chirp transformation analog technique Fourier transform real time multiplication-convolution configuration chirp filters time-bandwidth product signal spectrum dispersive delay liner passband 70 MHz SiO/sub 2/ }, mynotes={UNREAD}, } @ARTICLE{LawtonJul92, title={ Multidimensional chirp algorithms for computing Fourier transforms }, journal={IEEE Transactions on Image Processing}, volume={1}, number={3}, year={1992}, month={Jul}, pages={429-31}, abstract={ Continuous versions of the multidimensional chirp algorithms compute the function G(y)=F(My), where F(y) is the Fourier transform of a function f(x) of a vector variable x and M is an invertible matrix. Discrete versions of the algorithms compute values of F over the lattice L/sub 2/=ML/sub 1/ from values of f over a lattice L/sub 1/, where L/sub 2/ need not contain the lattice reciprocal to L/sub 1/. If M is symmetric, the algorithms are multidimensional versions of the Bluestein chirp algorithm, which employs two pointwise multiplication operations (PMOs) and one convolution operation (CO). The discrete version may be efficiently implemented using fast algorithms to compute the convolutions. If M is not symmetric, three modifications are required. First, the Fourier transform is factored as the product of two Fresnel transforms. Second, the matrix M is factored as M=AB, where A and B are symmetric matrices. Third, the Fresnel transforms are modified by the matrices A and B and each modified transform is factored into a product of two PMOs and one CO }, keywords={ fast Fourier transforms matrix algebra vectors discrete Fourier transform computation DFT multidimensional chirp algorithms invertible matrix M Bluestein chirp algorithm pointwise multiplication operations convolution operation fast algorithms Fresnel transforms symmetric matrices }, mynotes={UNREAD}, } @ARTICLE{JonesDec90, author={Jones, D.L. and Parks, T.W.}, title={ A high resolution data-adaptive time-frequency representation }, journal={IEEE Transactions on Acoustics, Speech and Signal Processing}, volume={38}, number={12}, year={1990}, month={Dec}, pages={2127-35}, abstract={ A data-adaptive time-frequency representation is developed that overcomes some limitations of the short-time Fourier transform, while avoiding the cross-terms that make the Wigner distribution and other bilinear representations difficult to interpret. The adaptive time-frequency representations uses Gaussian basis functions but varies their time width and chirp rate with time and frequency to achieve high signal concentration everywhere. A measure of local signal concentration allows fully automated determination of the optimal basis parameters. The adaptive method is computationally expensive, but may provide much better performance than any currently known technique }, keywords={ signal processing spectral analysis signal processing frequency analysis data-adaptive time-frequency representation short-time Fourier transform Gaussian basis functions time width chirp rate local signal concentration optimal basis parameters }, mynotes={UNREAD}, } @ARTICLE{JonesApr91, author={Jones, D.L. and Baraniuk, R.G.}, title={ Efficient approximation of continuous wavelet transforms }, journal={Electronics Letters}, volume={27}, number={9}, year={1991}, month={Apr}, pages={748-50}, abstract={ An efficient algorithm is developed for computing the continuous wavelet transform or wideband ambiguity function on a grid whose samples are spaced uniformly in time but placed arbitrarily in scale. The method is based on the chirp z transform and requires the same order of computation as constant-bandwidth analysis techniques, such as the short-time Fourier transform and narrowband ambiguity function }, keywords={ computational complexity signal processing transforms efficient algorithm continuous wavelet transform wideband ambiguity function chirp z transform order of computation }, mynotes={UNREAD}, } @ARTICLE{ChallisJan91, author={Challis, R.E. and Kitney, R.I.}, title={ Biomedical signal processing. II. The frequency transforms and their inter-relationships }, journal={Medical & Biological Engineering & Computing}, volume={29}, number={1}, year={1991}, month={Jan}, pages={1-17}, abstract={ For pt.I see ibid., vol.28, p.509 (1990). This tutorial paper on biomedical signal processing concerns the relationships between commonly used frequency transforms. It begins with the Fourier series and Fourier transform for continuous time signals and extends these concepts for aperiodic discrete time data and then periodic discrete time data. The Laplace transform is discussed as an extension of the Fourier transform. The Z-transform is introduced and the ideas behind the chirp-Z transform are described. The equivalence between the time and frequency domains is described in terms of Parseval's theorem and the theory of convolution. The use of the FFT for fast convolution and fast correlation is described for both short recordings and long recordings that must be processed in sections }, keywords={ biomedical measurement Fourier transforms Laplace transforms reviews signal processing Z transforms digital signal processing frequency transforms biomedical signal processing Fourier series Fourier transform continuous time signals aperiodic discrete time data periodic discrete time data Laplace transform Z-transform chirp-Z transform Parseval's theorem FFT fast convolution fast correlation }, mynotes={UNREAD}, } @ARTICLE{WangApr90, title={ The segmented chirp Z-transform and its application in spectrum analysis }, journal={IEEE Transactions on Instrumentation and Measurement}, volume={39}, number={2}, year={1990}, month={Apr}, pages={318-23}, abstract={ The chirp Z-transform (CZT) algorithm is known to be more flexible than the fast Fourier transform in calculating the frequency spectrum. However, its mathematical implementation is complex, and additional memory space is required. A modified CZT algorithm called the segmented chirp Z transform (SCZT) is introduced. SCZT has the ability to handle a very large amount of input data with very limited memory space and to limit its calculation to a portion of the frequency spectrum of interest with greatly increased dynamic range and frequency resolution }, keywords={ computerised signal processing spectral analysis Z transforms segmented algorithm instrumentation segmented chirp Z-transform spectrum analysis frequency spectrum }, mynotes={UNREAD}, } @CONFERENCE{Kobayashi88, title={ A fast method of chirp signal analysis }, booktitle={Signal Processing IV: Theories and Applications. Proceedings of EUSIPCO-88.Fourth European Signal Processing Conference}, volume={}, number={}, year={1988}, month={}, pages={383-6 vol.1}, abstract={ As a vehicle for time-varying signals analysis, a method is presented to determine the average frequency and chirp rate of a signal with an order of computation O(Nlog/sub 2/N+N/sup 2/), as contrasted to O(N/sup 2/log/sub 2/N) of the traditional method. The derived chirp-rate parameter could be used for data-adaptive windows for high-resolution Fourier transforms }, keywords={ fast Fourier transforms spectral analysis FFT spectral analysis chirp signal analysis time-varying signals frequency chirp rate order of computation data-adaptive windows high-resolution Fourier transforms }, mynotes={UNREAD}, } @ARTICLE{McIverMay89, author={McIver, R.T. and Jr., Baykut and G. and Hunter, R.L.}, title={ Theory of impulse excitation for Fourier transform mass spectrometry }, journal={International Journal of Mass Spectrometry and Ion Processes}, volume={89}, number={2-3}, year={1989}, month={May}, pages={343-58}, abstract={ Most Fourier transform mass spectrometer utilize a rapid radio frequency sweep, or 'chirp', to accelerate and detect ions. Impulse excitation is different because the ions are accelerated by a very short, high voltage DC pulse. In this paper, an analytical theory of impulse excitation is presented. Ion trajectories are plotted to illustrate the effects of pulse width, pulse height and 'risetime' and 'falltime' of the pulse on the ion motion. To minimize mass discrimination, the risetime of the impulse signal must be very fast (50-100 ns) and the pulse width must be much shorter than the period of the cyclotron orbit of an ion }, keywords={ Fourier transform spectroscopy mass spectroscopy ion acceleration ion detection ion trajectories impulse excitation Fourier transform mass spectrometry Fourier transform mass spectrometer radio frequency sweep DC pulse pulse width pulse height falltime ion motion mass discrimination risetime impulse signal cyclotron orbit }, mynotes={UNREAD}, } @CONFERENCE{Gibbins89, title={ Atmospheric effects on the propagation of very short pulses at millimetric wavelengths }, booktitle={Sixth International Conference on Antennas and Propagation (ICAP 89) (Conf.Publ. No.301)}, volume={}, number={}, year={1989}, month={}, pages={432-6 vol.2}, abstract={ An alternative approach to the solution of the Fourier integral in closed form was adopted by Terina (1967) for reflections from the ionosphere of pulsed HF (3-6 MHz) transmissions. This technique, appropriate to any line shape, assumes that the atmospheric channel transfer function can be approximated by a truncated Taylor series of frequency; its validity thus relies on the presumption that high-order terms can be neglected. Although this may not be strictly valid at frequencies very close to resonant absorption lines, the treatment allows an examination of a variety of phenomena arising from the dispersive nature of the atmosphere, such as the imposition of frequency modulation (chirp) on the carrier frequency within the pulse and the corresponding changes in the spectrum which arise through the frequency-dependent group velocity. This analysis has been considered briefly for line-of-sight transmissions near 55 GHz by Medeiros Filho et al (1983). The paper extends this to investigate absorptive and dispersive effects on pulses at carrier frequencies between 10 and 200 GHz, for pulse widths between 2 ns and 0.1 ns, for line-of-sight pathlengths from 1 to 50 km, and along Earth-space paths }, keywords={ atmospheric electromagnetic wave propagation electromagnetic pulse radiowave propagation very short pulses propagation SHF EHF millimetric wavelengths reflections ionosphere atmospheric channel transfer function truncated Taylor series frequency modulation chirp carrier frequency group velocity line-of-sight transmissions dispersive effects pulse widths Earth-space paths 3 to 6 MHz 10 to 200 GHz 0.1 to 10 ns 1 to 50 km }, mynotes={UNREAD}, } @ARTICLE{PooleNov85, title={ Advanced sounding. I. The FMCW alternative }, journal={Radio Science}, volume={20}, number={6}, year={1985}, month={Nov}, pages={1609-16}, abstract={ HF radar employing linear frequency-modulated continuous wave or 'chirp' modulation provides an alternative to the more conventional pulsed amplitude modulation technique in advanced ionosphere sounding. An analysis is presented which shows that the phases of the discrete Fourier components of the receiver output can be used in the same fashion as the phases of pulsed, fixed frequency ionospheric echoes to evaluate the standard digital parameters, including group path by the method of stationary phase. This can be used to overcome the group path/Doppler velocity ambiguity of linear frequency modulation. A description is given of a sounding structure from which unambiguous group range, angle of arrival, O/X mode, and Doppler velocity can be evaluated. A simple error analysis is also given }, keywords={ ionospheric electromagnetic wave propagation ionospheric measuring apparatus ionospheric techniques radar systems radiowave propagation chirp modulation polarization mode HF radar linear frequency-modulated continuous wave advanced ionosphere sounding Fourier components receiver output group path stationary phase Doppler velocity group range angle of arrival error analysis }, mynotes={UNREAD}, } @ARTICLE{ZakareviciusMar81, title={ Chirp waveforms and signal processing }, journal={Journal of Electrical and Electronics Engineering, Australia}, volume={1}, number={1}, year={1981}, month={Mar}, pages={93-8}, abstract={ Chirp waveforms are waveforms with a carrier frequency which varies linearly with time. They can be employed in various signal processing operations, the most important of which is Fourier Transformation. Other applications include signal compression/dilation, time reversal and electronically variable time delay, all of which can be achieved with no signal distortion. This paper takes a tutorial approach to explain the role of chirp waveforms in these signal processing operations and their practical applications. Whenever possible, the underlying physical principles are emphasised }, keywords={ Fourier analysis Fourier transforms signal processing signal processing Fourier Transformation chirp waveforms practical applications physical principles }, mynotes={UNREAD}, } @ARTICLE{QuatieriDec78, title={ Short-time spectral analysis with the conventional and sliding CZT }, journal={IEEE Transactions on Acoustics, Speech and Signal Processing}, volume={ASSP-26}, number={6}, year={1978}, month={Dec}, pages={561-6}, abstract={ Two sequential short-time spectral analysis techniques, amenable to nonrecursive filter implementation, are the conventional chirp-z-transform (CZT) realization of the discrete Fourier transform and the sliding CZT realization of the discrete sliding Fourier transform. This paper presents a comparative study of frame rate limitations, windowing, time and frequency resolution, spectral correlation, complexity, and inverse structures for these methods, with particular emphasis on the recently proposed sliding transform. The sliding transform and its CZT realization are viewed as skewed output samples of a filter bank, an approach which aids in understanding the relationship between the conventional and sliding schemes. Numerous forward and inverse CZT formulations are presented to improve resolution, frame rates, and compactness }, keywords={ Fourier transforms spectral analysis Z transforms discrete Fourier transform CZT realization discrete sliding Fourier transform frame rate limitations windowing frequency resolution spectral correlation complexity inverse structures signal processing short time spectral analysis chirp z-transform }, mynotes={UNREAD}, } @ARTICLE{ZakareviciusMay77, title={ Signal processing with fast chirp waveforms }, journal={Electronics Letters}, volume={13}, number={10}, year={1977}, month={May}, pages={296-7}, abstract={ The analysis shows that the implementation with chirp waveforms of the operations of time compression and variable delay of signals can be significantly simplified if fast rates of chirp are used. A related simplification for Fourier transformation is also presented }, keywords={ signal processing fast chirp waveforms time compression variable delay Fourier transformation signal processing }, mynotes={UNREAD}, } @ARTICLE{BlochJul73, title={ Introduction to chirp concepts with a cheap chirp radar }, journal={American Journal of Physics}, volume={41}, number={7}, year={1973}, month={Jul}, pages={857-64}, abstract={ The elements of pulse compression of a chirp in a dispersive delay are reviewed and chirp and pulse modes are contrasted. A simple microwave Doppler-shift apparatus is modified into a chirp system to permit distance measurement in a laboratory experiment that is rich in fundamental concepts of physical parameters which are related by the Fourier transform, and which involve the convergence of ideas from several disciplines }, keywords={ demonstrations distance measurement radar chirp concepts chirp radar pulse compression pulse modes distance measurement Fourier transform microwave Doppler shift apparatus }, mynotes={UNREAD}, } @ARTICLE{RabinerMay69, author={Rabiner, L.R. and Schafer, R.W. and Rader, C.M.}, title={ The chirp z-transform algorithm and its application }, journal={Bell System Technical Journal}, volume={48}, number={5}, year={1969}, month={May}, pages={1249-92}, abstract={ A computational algorithm is discussed for numerically evaluating the z-transform of a sequence of N samples. This algorithm has been named the chirp z-transform algorithm. Using this algorithm one can efficiently evaluate the z-transform at M points in the z-plane which lie on circular or spiral contours beginning at any arbitrary point in the z-plane. The angular spacing of the points is an arbitrary constant; M and N are arbitrary integers. The algorithm is based on the fact that the values of the z-transform on a circular or spiral contour can be expressed as a discrete convolution. Thus one can use well-known high-speed convolution techniques to evaluate the transform efficiently. For M and N moderately large, the computation time is roughly proportional to (N+M) log/sub 2/ (N+M) as opposed to being proportional to N.M for direct evaluation of the z-transform at M points. Applications discussed include: enhancement of poles in spectral analysis, high resolution narrow-band frequency analysis, interpolation of band-limited waveforms, and the conversion of a base 2 fast Fourier transform program into an arbitrary radix fast Fourier transform program }, keywords={ numerical analysis subroutines Z transforms }, mynotes={UNREAD}, } @ARTICLE{Hamed97, author={Hamed, Z.F. and Flores, B.C.}, title={ Wideband spectral reconstruction via short-time modified chirp z-transform processing }, journal={Proc. SPIE - Int. Soc. Opt. Eng. (USA), Proceedings of the SPIE - TheInternational Society for Optical Engineering}, volume={3161}, number={}, year={1997}, month={}, pages={113-24}, abstract={ The chirp z-transform is adapted for the spectral reconstruction of a wideband signal. Here, spectral reconstruction is based on the coherent and sequential processing of non-overlapping short-time segments. This approach eases hardware implementation in the presence of limited memory allocation and can provide savings in computational effort. In addition, it offers the flexibility of focusing the reconstruction of the spectrum on a narrow spectral band of interest }, keywords={ coherence discrete Fourier transforms signal reconstruction spectral analysis Z transforms wideband spectral reconstruction short-time modified chirp z-transform processing wideband signal sequential processing coherent processing nonoverlapping short-time segments hardware implementation limited memory allocation computational effort savings narrow spectral band FFT DFT }, mynotes={UNREAD}, } @ARTICLE{Wang-JingDec97, author={Wang Jing, Miao Hongli and Liu Xiumin, Feng Lu and Feng Qiyuan}, title={ The evolution of chirp in normal-dispersion near the zero-dispersion wavelength in the single-mode fibers }, journal={Acta Photonica Sinica}, volume={26}, number={12}, year={1997}, month={Dec}, pages={1082-5}, abstract={ Taken into account second and third order dispersion in the normal-dispersion region of single-mode fibers by means of Fourier-transform algorithm, an analytic expression of the dispersion-induced chirp is obtained. The results show that chirp is nonlinear and has extreme value, it is shown that pulse distortion is induced by chirp }, keywords={ chirp modulation Fourier transform optics optical fibre communication optical fibre dispersion optical fibre theory normal-dispersion zero-dispersion wavelength single-mode fibers chirp modulation normal-dispersion region Fourier-transform algorithm dispersion-induced chirp pulse distortion optical fibre communication }, mynotes={UNREAD}, } @CONFERENCE{Ikram96, author={Ikram, M.Z. and Abed-Meraim, K. and Yingbo Hua}, title={ An iterative approach to the parametric estimation of chirp signals }, booktitle={1996 IEEE TENCON Digital Signal Processing Applications Proceedings (Cat.No.96CH36007)}, volume={}, number={}, year={1996}, month={}, pages={681-5 vol.2}, abstract={ This paper considers the problem of estimating the parameters of a chirp signal from a finite number of noisy discrete time observations. A new iterative method is proposed that proceeds in two steps where the first step consists of estimating iteratively the second order phase coefficient using a properly chosen lagged sequence. The resulting sequence is shown to be time series harmonic, the harmonic frequency being a linear function of the chirp parameters. The iterative procedure is repeated until significantly accurate results are obtained. The second step consists of estimating (iteratively or not) the first order phase coefficient using a properly chosen quadratic transform of the chirp signal. The efficacy of the method is demonstrated by some numerical simulations }, keywords={ chirp modulation discrete time systems harmonic analysis iterative methods noise phase estimation sequences time series iterative approach parametric estimation chirp signals noisy discrete time observations second order phase coefficient lagged sequence time series harmonics harmonic frequency first order phase coefficient quadratic transform }, mynotes={UNREAD}, } @CONFERENCE{Frickey94, title={ Using the inverse chirp-Z transform for time-domain analysis of simulated radar signals }, booktitle={Proceedings of the 5th International Conference on Signal ProcessingApplications and Technology}, volume={}, number={}, year={1994}, month={}, pages={1366-71 vol.2}, abstract={ There exists a need to develop a method to locate underground voids, or caches. In the past, ground penetrating radar (GPR) operating in the time domain mode has been used. In this paper, we turn our attention to stepped frequency radar, capable of making frequency domain reflection coefficient measurements. We then apply the inverse chirp-Z transform (ICZT) to this data, generating a time domain response. The scenario under consideration is that of an airborne radar passing over the surface of the Earth. The radar is directed toward the surface and is capable of measuring the reflection coefficient, seen looking toward the Earth, as a function of frequency. The frequency domain data in this work is simulated and is generated from a transmission line model of the problem. Using the ICZT we convert this frequency domain data to the time domain. Once in the time domain, reflections due to discontinuities appear at times indicating their relative distance from the source. The discontinuities occurring beyond the surface of the earth could be indicative of underground structures. The ICZT allows a person to zoom in on the time span of interest by specifying the starting time, the time resolution, and the number of time steps }, keywords={ airborne radar electromagnetic wave reflection radar signal processing time-domain analysis transmission line theory Z transforms inverse chirp-Z transform time-domain analysis simulated radar signals underground void ground penetrating radar stepped frequency radar frequency domain reflection coefficient measurements time domain response airborne radar frequency domain data transmission line model ICZT underground structures starting time time resolution }, mynotes={UNREAD}, } @ARTICLE{RisticSep95, author={Ristic, B. and Boashash, B.}, title={ Signal dependent time-frequency and time-scale signal representations designed using the Radon transform }, journal={IEICE Transactions on Fundamentals of Electronics, Communications andComputer Sciences}, volume={E78-A}, number={9}, year={1995}, month={Sep}, pages={1170-7}, abstract={ Time-frequency representations (TFRs) have been developed as tools for analysis of non-stationary signals. Signal dependent TFRs are known to perform well for a much wider range of signals than any fixed (signal independent) TFR. This paper describes customised and sequential versions of the signal dependent TFR. The method, which is based on the use of the Radon transform at distance zero in the ambiguity domain, is simple and effective in dealing with both simulated and real data. The use of the described method for time-scale analysis is also presented. In addition, the paper investigates a simple technique for detection of noisy chirp signals using the Radon transform in the ambiguity domain }, keywords={ chirp modulation Radon transforms signal representation time-frequency analysis time-frequency signal representations time-scale signal representations Radon transform nonstationary signals signal dependent TFRs sequential version ambiguity domain noisy chirp signals }, mynotes={UNREAD}, } @CONFERENCE{Azouz94, author={Azouz, A. and Stelmakh, N. and Langlois, P. and Lourtioz, J.-M. and Gavrilovic, P.}, title={ Nonlinear chirp compensation in high-power (>100 W) broad spectrum ( approximately 20 nm) pulses from mode-locked AlGaAs lasers }, booktitle={14th IEEE International Semiconductor Laser Conference (Cat. No.94CH3379-5)}, volume={}, number={}, year={1994}, month={}, pages={233-4}, abstract={ In this paper, we show that very broad pulse spectra (20 nm) can be effectively obtained by active/hybrid mode-locking of long-stripe (1 mm) high-power AlGaAs laser diodes, the spectral widths corresponding in principle to sub-100 fs pulses in the transform-limit situation. A novel technique is presented in order to analyze chirp non-linearities (i.e, high-order dispersion effects) in the laser pulses. Second- and third-order dispersion compensation is realized with an external compressor, leading to 160 fs pulses after compression with peak powers in excess of 100 W }, keywords={ aluminium compounds chirp modulation compensation electro-optical modulation gallium arsenide high-speed optical techniques III-V semiconductors laser mode locking nonlinear optics optical dispersion optical pulse compression quantum well lasers spectral line breadth nonlinear chirp compensation high-power broad spectrum pulses mode-locked AlGaAs lasers active mode-locking hybrid mode-locking long-stripe high-power AlGaAs laser diodes spectral widths sub-100 fs pulses transform-limit situation chirp nonlinearities high-order dispersion effects laser pulses third-order dispersion compensation external compressor peak powers laser mode locking 100 W 100 fs 160 fs AlGaAs }, mynotes={UNREAD}, } @ARTICLE{NorcrossSep94, author={Norcross, S. and Bradley, J.S.}, title={ Comparison of room impulse response measurement methods }, journal={Can. Acoust. (Canada), Canadian Acoustics}, volume={22}, number={3}, year={1994}, month={Sep}, pages={47-8}, abstract={ One of the most important measures of a system such as a room is impulse response. Almost all characteristics of that system can be calculated directly from the impulse response, i.e. in room acoustics numerous objective parameters such as reverberation time, early/late ratios and RASTI can all be obtained from it. In room acoustics, due to large reverberation times, longer impulse responses are needed and a large dynamic is desired. The impulse response of a system is defined as the output when a perfect pulse, or delta function, is applied to it. Hence, the simplest of all techniques is just to apply a short duration pulse to the room and then measure its response. Other broadband signals can be used, with various processing, to calculate the impulse response. One example is the use of a chirp, a short duration sine sweep. This approach has more energy output than a pulse, but requires post-processing. If one stretches out the chirp so that it is a continuous repeating sweep, even more energy is output, and this requires similar post-processing. Finally, a pseudorandom noise, or a maximum-length sequence signal, with a Fast Hadamard transform can be used, to calculate the impulse response. For all of these techniques to be valid, the system under study must be linear and time invariant (except with the pulse method where time invariant is not a problem). This paper compares each of these approaches, and describes the strengths and weaknesses of them when applied to room acoustics }, keywords={ acoustic variables measurement architectural acoustics room impulse response measurement methods room acoustics reverberation times broadband signals short duration sine sweep post-processing pseudorandom noise maximum-length sequence signal Fast Hadamard transform }, mynotes={UNREAD}, } @ARTICLE{Loe94, author={Loe, R.S. and Anderson, K. and Jung, K.}, title={ Comparative analysis results for underwater transient classification }, journal={Proc. SPIE - Int. Soc. Opt. Eng. (USA), Proceedings of the SPIE - TheInternational Society for Optical Engineering}, volume={2242}, number={}, year={1994}, month={}, pages={815-23}, abstract={ Comparative results are presented for the classification of underwater transient sounds. Comparisons are made using the short-time Fourier transform (STFT) and the Morlet continuous wavelet transform (CWT). Performance as a function of signal to noise ratio are presented for synthetic chirp transients. Classification results for three classes of biological signals are also presented. Both adaptive energy windows and moments of the transformed signals were used as features for classification. Certain classes of transient signals were found for which one of the transforms was superior. In general wavelets were better for broadband signals while the STFT was optimal on narrowband signals }, keywords={ acoustic signal processing fast Fourier transforms pattern recognition transients underwater sound wavelet transforms underwater transient classification underwater transient sounds short-time Fourier transform STFT Morlet continuous wavelet transform CWT signal to noise ratio synthetic chirp transients classification results biological signals adaptive energy windows moments wavelets broadband signals narrowband signals }, mynotes={UNREAD}, } @ARTICLE{CohenNov93, author={Cohen, F.S. and Kadambe, S. and Boudreaux-Bartels, G.F.}, title={ Tracking of unknown nonstationary chirp signals using unsupervised clustering in the Wigner distribution space }, journal={IEEE Transactions on Signal Processing}, volume={41}, number={11}, year={1993}, month={Nov}, pages={3085-101}, abstract={ This paper is concerned with the problems of (1) detecting the presence of one or more FM chirp signals embedded in noise, and (2) tracking or estimating the unknown, time-varying instantaneous frequency of each chirp component. No prior knowledge is assumed about the number of chirp signals present, the parameters of each chirp, or how the parameters change with time. A detection/estimation algorithm is proposed that uses the Wigner distribution transform to find the best piecewise cubic approximation to each chirp's phase function. The first step of the WD based algorithm consists of properly thresholding the WD of the received signal to produce contours in the time-frequency plane that approximate the instantaneous frequency of each chirp component. These contours can then be approximated as generalized lines in the ( omega , t, t/sup 2/) space. The number of chirp signals (or equivalently, generalized lines) present is determined using maximum likelihood segmentation. Minimum mean square estimation techniques are used to estimate the unknown phase parameters of each chirp component. The authors demonstrate that for the cases of (i) nonoverlapping linear or nonlinear FM chirp signals embedded in noise or (ii) overlapping linear FM chirp signals embedded in noise, the approach is very robust, highly reliable, and can operate efficiently in low signal-to-noise environments where it is hard for even trained operators to detect the presence of chirps while looking at the WD plots of the overall signal. For multicomponent signals, the proposed technique is able to suppress noise as well as the troublesome cross WD components that arise due to the bilinear nature of the WD }, keywords={ frequency modulation maximum likelihood estimation signal detection time-frequency analysis tracking transforms nonstationary chirp signals unsupervised clustering Wigner distribution space linear FM chirp signals tracking time-varying instantaneous frequency detection/estimation algorithm Wigner distribution transform piecewise cubic approximation phase function received signal time-frequency plane nonlinear FM chirp signals overlapping signals signal-to-noise multicomponent signals noise suppression nonoverlapping signals }, mynotes={UNREAD}, } @ARTICLE{BettaAug93, author={Betta, G. and Daponte, P.}, title={ Detection of echoes in noisy environments for multilayer structure characterization }, journal={IEEE Transactions on Instrumentation and Measurement}, volume={42}, number={4}, year={1993}, month={Aug}, pages={834-41}, abstract={ Digital signal processing techniques set up to detect echoes in noisy environments and to thus carry out thickness measurements in thin multilayer structures are discussed. In particular, the cepstrum and the segmented chirp Z-transform are analyzed and compared, highlighting their performances in relation to noise characteristics. A suitable operating procedure was set up, based on an initial emulation phase in which simulated signals are considered, followed by a second phase in which signals were processed. The results show that optimum performances can be achieved by using the segmented chirp Z-transform together with a high flexible window }, keywords={ biological techniques and instruments computerised instrumentation echo random noise signal processing signal processing equipment thickness measurement ultrasonic applications wave analysers Z transforms digital signal processing waveform analyser waveform synthesizer US signal eye echoes noisy environments thickness measurements thin multilayer structures cepstrum segmented chirp Z-transform noise characteristics optimum performances }, mynotes={UNREAD}, } @ARTICLE{SeasJul92, author={Seas, A. and Petricevic, V. and Alfano, R.R.}, title={ Generation of sub-100-fs pulses from a CW mode-locked chromium-doped forsterite laser }, journal={Optics Letters}, volume={17}, number={13}, year={1992}, month={Jul}, pages={937-9}, abstract={ Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite (Cr/sup 4+/:Mg/sub 2/SiO/sub 4/) laser is reported. The forsterite laser was actively mode locked by using an acousto-optic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intracavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM/sub 00/ mode with 85 mW of continuous power (with 1% output coupler), tunable over 1230-80 nm. The shortest pulses measured had a 60-fs pulse width }, keywords={ acousto-optical devices chromium high-speed optical techniques laser mode locking magnesium compounds optical modulation solid lasers transverse electromagnetic mode pulse generation transform limited femtosecond pulses femtosecond pulses acousto-optic modulator Brewster high-dispersion glass prisms intracavity chirp compensation continuous power tunable pulse width 78 MHz 85 mW 1230 to 1280 nm 60 fs continuous wave mode locked Mg/sub 2/SiO/sub 4/:Cr/sup 4+/ forsterite laser [I] }, mynotes={UNREAD}, } @ARTICLE{LiMay91, author={Li, Y.L. and Franke, S.J. and Liu, C.H.}, title={ Numerical implementation of an adaptive fast-field program for sound propagation in layered media using the chirp z transform }, journal={Journal of the Acoustical Society of America}, volume={89}, number={5}, year={1991}, month={May}, pages={2068-75}, abstract={ Using the chirp z transform, a numerically efficient adaptive integration algorithm for fast-field programs has been developed. The fast-field program (FFP) is a numerically efficient algorithm for computation of the sound pressure due to a time harmonic point source above a general boundary in a layered medium. The new algorithm allows the user to specify the precise location of the range sample points, or 'detectors', independent of the horizontal wave-number sampling grid. This feature makes the algorithm particularly attractive for use in applications where sampling on a predetermined spatial grid is required. An example of such an application is the computation of the acoustic frequency response as a function of range. In this case the complex sound pressure must be computed at many frequencies while maintaining a constant range sampling interval. In addition, the algorithm can be used to recompute the sound pressure field with different range resolutions without recomputing the horizontal wavenumber spectrum samples. It is also shown that the algorithm can be used to adaptively increase the number of integration points required to evaluate the Sommerfeld integral that results from the FFP type of formulation }, keywords={ acoustic wave propagation fast Fourier transforms chirp z transform adaptive integration algorithm fast-field programs sound pressure time harmonic point source horizontal wave-number sampling grid Sommerfeld integral }, mynotes={UNREAD}, } @CONFERENCE{Gertner90, title={ Optimal detection and separation of chirp signals }, booktitle={ICASSP 90. 1990 International Conference on Acoustics, Speech and SignalProcessing (Cat. No.90CH2847-2)}, volume={}, number={}, year={1990}, month={}, pages={2507-10 vol.5}, abstract={ The finite Zak transform is introduced into the problem of signal detection in a noisy environment. The main advantage of the Zak transform over the Wigner distribution approach is the linearity. Thus there are no cross terms in a multicomponent signal environment. The theory has been applied to separate chirp signals }, keywords={ signal detection signal processing transforms signal separation optimal detection chirp signals finite Zak transform signal detection noisy environment }, mynotes={UNREAD}, } @CONFERENCE{Hull90, author={Hull, A.W. and Jenkins, W.K.}, title={ Transform domain adaptive filtering with the chirp Z transform }, booktitle={ICASSP 90. 1990 International Conference on Acoustics, Speech and SignalProcessing (Cat. No.90CH2847-2)}, volume={}, number={}, year={1990}, month={}, pages={1437-40 vol.3}, abstract={ The use of the chirp Z transform (CZT) is proposed to improve the rate of convergence of transform domain adaptive output error algorithms. The use of the CZT is novel and is shown to possess advantages over the DFT. Other attempts at incorporating prior knowledge of input spectra use frequency sampling structures and their generalizations. Such structures require pole-zero cancellation, which is inexact with finite word length and may lead to instability if a zero occurs on the unit circle. Use of the CZT eliminates these difficulties and provides a stable, rapidly converging solution }, keywords={ adaptive filters convergence of numerical methods filtering and prediction theory Z transforms transform domain adaptive filtering chirp Z transform CZT rate of convergence transform domain adaptive output error algorithms frequency sampling structures pole-zero cancellation }, mynotes={UNREAD}, } @CONFERENCE{Stearns89, title={ Detection of a chirping electromagnetic signal }, booktitle={Conference Record. Twenty-Third Asilomar Conference on Signals, Systemsands Computers (IEEE Cat. No.89-CH2836-5)}, volume={}, number={}, year={1989}, month={}, pages={216-19 vol.1}, abstract={ A matched chirp transform (MCT) method for detecting a dispersive electromagnetic pulse is described. The unique feature of this transform is that it gives a distribution of signal amplitude over time rather than frequency, thereby simplifying signal detection and identification in the case described. In the MCT method, the incoming signal is matched to a set of signal segments that chirp in accordance with an expected model of the dispersive medium. The performance of the MCT method is compared to that of a standard periodogram method of frequency measurement }, keywords={ signal detection transforms chirping electromagnetic signal matched chirp transform dispersive electromagnetic pulse signal amplitude signal detection identification signal segments standard periodogram method frequency measurement }, mynotes={UNREAD}, } @CONFERENCE{Kohri87, author={Kohri, T. and Morikura, M. and Kato, S.}, title={ A 400 ch SCPC signal demodulator using chirp transform and correlation detection scheme }, booktitle={GLOBECOM Tokyo '87. IEEE/IECE Global Telecommunications Conference 1987.Conference Record (Cat. No.87CH2520-5)}, volume={}, number={}, year={1987}, month={}, pages={286-91 vol.1}, abstract={ A group demodulator for PSK-FDMA (phase-shift-keyed frequency-division multiple access) signals using a chirp transform is proposed for hardware and power consumption reduction of demodulators at a hub station. The proposed demodulator uses a chirp filter for FDM/TDM transform of received PSK-FDMA signals and demodulates TDM transform signals by recovering each channel carrier and clock. Since the chirp filter works as an analog correlator, the transform TDM signals have the maximum S/N (signal-to-noise) ratio at the sampling instant, achieving 2 b/s/Hz frequency utilization efficiency with a QPSK (quadrature phase-shift keyed) modulation scheme. The feasibility test results on the prototype 400-channel demodulator show a good agreement with theory. The proposed group demodulator can contribute to reduce significantly hardware size and power consumption of hub stations }, keywords={ correlation methods demodulation frequency division multiplexing multi-access systems phase shift keying satellite relay systems signal processing SCPC signal demodulator chirp transform correlation detection scheme group demodulator PSK-FDMA power consumption reduction hub station chirp filter QPSK }, mynotes={UNREAD}, } @CONFERENCE{Vickers86, author={Vickers, H. and Johnson, K.P.}, title={ Ultra-wideband chirp Fourier transform processor }, booktitle={MILCOM 86: 1986 IEEE Military Communications Conference.Communications-Computers: Teamed for the '90's. Conference Record (Cat.No.86CH2323-4)}, volume={}, number={}, year={1986}, month={}, pages={6.3/1-5 vol.1}, abstract={ A chirp Fourier transform (CFT) processor is described which establishes new performance levels for wideband signal processing. The CFT module accepts analog signals in an 80 MHz bandwidth over a 10 mu s input observation frame, computes the Fourier transform and outputs the baseband spectra in 12 bit digital I (in-phase), Q (quadrature) format to a frequency domain processor; processing rate is equivalent to 400 MCOPS. This module, offering a combination of state-of-the-art analog and digital circuit techniques, removes the oven requirement for temperature stabilization of LiNbO/sub 3/ surface acoustic wave devices, while matching their wideband performance with the latest advances in digital signal processing devices. Applications include communications equipment such as JTIDS, EW, and radar systems., }, keywords={ Fourier transforms signal processing surface acoustic wave devices SAW devices chirp Fourier transform processor wideband signal processing analog signals baseband spectra frequency domain processor processing rate digital circuit digital signal processing devices communications equipment JTIDS EW radar systems 50 MHz 10 mus LiNbO/sub 3/ }, mynotes={UNREAD}, } @CONFERENCE{Griffiths86, title={ A novel window for high-resolution Fourier transforms }, booktitle={Conference Record. Nineteenth Asilomar Conference on Circuits, Systems andComputers (Cat. No.86CH2331-7)}, volume={}, number={}, year={1986}, month={}, pages={621-5}, abstract={ A data multiplication window is suggested for use with the Fourier transform that is complex and consists of a linear frequency-modulated chirp which spans the range 0 to 2 pi . Windowing in this manner is shown to be particularly useful for complex data signals such as those observed at the outputs of in-phase and quadrature component receivers. As such, it has application to both communications and radar problems. For the case of an input consisting of a single complex sinusoid, the window produces an extremely sharp null located exactly at the frequency of the input sinusoid. As such, it has resolution properties far superior to those available via more conventional windowing techniques such as the raised cosine. Examples are presented showing clear indications of frequency shifts as small as 1/8 bin. Applications to real data environments are discussed }, keywords={ Fourier transforms high-resolution Fourier transforms data multiplication window linear frequency-modulated chirp complex data signals radar problems windowing techniques frequency shifts data environments }, mynotes={UNREAD}, } @ARTICLE{EastonNov85, author={Easton, R.L. and Jr., Ticknor and A.J. and Barrett, H.H.}, title={ Two-dimensional complex Fourier transform via the Radon transform }, journal={Applied Optics}, volume={24}, number={22}, year={1985}, month={Nov}, pages={3817-24}, abstract={ A hybrid system has been constructed to perform the complex Fourier transform of real 2-D data. The system is based on the Radon transform; i.e. operations are performed on 1-D projections of the data. The projections are derived optically from transmissive or reflective objects, and the complex Fourier transform is performed with SAW filters via the chirp transform algorithm. The real and imaginary parts of the 2-D transform are produced in two bipolar output channels }, keywords={ Fourier transform optics optical information processing spatial filters surface acoustic wave devices 2D complex Fourier transform 1D projections transmissive objects surface acoustic wave filters Radon transform hybrid system reflective objects chirp transform algorithm bipolar output channels }, mynotes={UNREAD}, } @CONFERENCE{Patterson83, author={Patterson, M.S. and Karaylianis, N.E. and Geiger, T.F. and Casseday, M.W. and Berg, N.J.}, title={ Chirp Z-transform filter }, booktitle={1983 Ultrasonics Symposium Proceedings}, volume={}, number={}, year={1983}, month={}, pages={175-80 vol.1}, abstract={ An adaptive band-rejection filter based on the multiply-convolved chirp-Z transform algorithm was built using surface-acoustic-wave reflective array compressors (RACs). This filter can automatically excise over 150 narrow-band signals from a 30-MHz instantaneous signal bandwidth. The filter is used as a predetection signal processor in each channel of a two-channel cross-correlation receiver; the filter output frequency must track channel-to-channel to about 1 part in 10/sup 8/. The filter design allows the use of the same types of RAC for chirp generation, signal compression, and signal expansion, thereby reducing the time-frequency errors associated with designs using dissimilar devices. The use of a stabilized oven reduces temperature effects, and an automatic error correction scheme further increases frequency tracking. The maximum transform-domain sidelobe level is -50 dB. However, RAC amplitude and phase errors limit the compressed signal sidelobe level to -40 dB. Main-lobe excision in the transform domain results in a narrowband signal suppression of -38 dB. The spurious free-dynamic input signal and output signal range (without excision) is 55 dB }, keywords={ band-stop filters filtering and prediction theory surface acoustic wave devices Z transforms instantaneous signal bandwidth 30 MHz amplitude errors chirp 2-transform filter SAW reflective array compressors low level exciser adaptive band-rejection filter multiply-convolved chirp-Z transform algorithm surface-acoustic-wave reflective array compressors RACs narrow-band signals predetection signal processor two-channel cross-correlation receiver filter output frequency track channel-to-channel filter design chirp generation signal compression signal expansion time-frequency errors stabilized oven automatic error correction scheme frequency tracking maximum transform-domain sidelobe level phase errors compressed signal sidelobe level transform domain narrowband signal suppression spurious free-dynamic input signal output signal }, mynotes={UNREAD}, } @ARTICLE{KatesFeb83, title={ An auditory spectral analysis model using the chirp z-transform }, journal={IEEE Transactions on Acoustics, Speech and Signal Processing}, volume={ASSP-31}, number={1}, year={1983}, month={Feb}, pages={148-56}, abstract={ Discusses a new signal-processing approach to implementing an auditory processing model. The model is based on auditory physiology and psychophysics; it uses constant-bandwidth analysis below 500 Hz and constant-Q analysis above 500 Hz, with the analysis filters being implemented with multiple real poles. The constant-Q analysis is performed using the chirp z-transform (CZT). The author reviews the evidence for the auditory model and the properties of constant-Q analysis, and derive the CZT formulation for both causal and linear-phase analysis filters. The author concludes with an example of speech illustrating the use of the auditory model }, keywords={ acoustic signal processing hearing Z transforms auditory spectral analysis chirp z-transform signal-processing auditory processing model auditory physiology psychophysics constant-bandwidth analysis analysis filters multiple real poles constant-Q analysis linear-phase analysis filters speech }, mynotes={UNREAD}, } @ARTICLE{LamApr81, author={Lam, F.K. and Tsang, W.M.}, title={ Variable frequency filtering via chirp transform }, journal={International Journal of Electrical Engineering Education}, volume={18}, number={2}, year={1981}, month={Apr}, pages={139-46}, abstract={ A simple programmable chirp-transform band-pass and/or band-stop filter has been implemented using ultrasonic strip dispersive delay lines. Experimental results demonstrating the capability of the system are presented. In addition to processing applications the system may also be employed as a teaching tool for illustrating concepts in spectral analysis }, keywords={ passive filters strip lines teaching transforms ultrasonic delay lines chirp transform ultrasonic strip dispersive delay lines teaching spectral analysis variable frequency filtering bandpass bandstop }, mynotes={UNREAD}, } @CONFERENCE{Aylor80, author={Aylor, J.H. and McDonald, W.E. and Parrish, E.A., Jr.}, title={ Analysis of speech waveforms with the conventional and sliding CZT }, booktitle={12th Annual Southeastern Symposium on System Theory}, volume={}, number={}, year={1980}, month={}, pages={163-7}, abstract={ The discrete Fourier transform (DFT) is used extensively in digital processing of speech. The DFT is usually calculated by the FFT in digital hardware. The introduction of the CCD transversal filter offers an alternative to an all digital implementation of this important function for smaller systems where cost or power conservation is important. The filters calculate the DFT through use of the Chirp-Z transform algorithm which can yield an exact result. An alternative to the DFT is the discrete sliding Fourier transform (DSFT) which can also be calculated by CCD filters through use of the sliding Chirp-Z transform. The DSFT yields results which are not exactly equal to the DFT unless the signal is periodic, a condition not met by speech. By averaging periodograms, the DSFT can yield power spectral estimates for speech which approach those obtained with the DFT }, keywords={ speech analysis waveform analysis Z transforms discrete Fourier transform CCD transversal filter Chirp-Z transform algorithm discrete sliding Fourier transform averaging periodograms power spectral estimates speech waveforms analysis }, mynotes={UNREAD}, } @ARTICLE{MacphersonJan80, author={Macpherson, P.C. and Meldrum, S.J. and Tunstall-Pedoe, D.S.}, title={ A real-time spectrum analyser for ultrasonic Doppler signals, using a chirp-z-transform technique }, journal={Journal of Medical Engineering & Technology}, volume={4}, number={1}, year={1980}, month={Jan}, pages={24-6}, abstract={ A real-time Doppler spectral display has been developed using integrated circuits to implement a chirp-z-transform. The prototype system consists of the spectrum analyser, an ECG mixer and interface circuits for a display and fibre optic recorder. The analyser calculates spectral components using a type of discrete Fourier transform, known as the chirp-z-transform, which is particularly suited to the capabilities of transversal filters using charge coupled device technology. The analysis is controlled by a clock that commands the regular sampling of the Doppler signal, and a counter which controls the sequence of operations required for the transform }, keywords={ biomedical electronics biomedical ultrasonics Doppler effect spectral analysers ECG mixer interface circuits display fibre optic recorder discrete Fourier transform charge coupled device technology chirp z transform technique real time spectrum analyser biomedical ultrasonics blood velocity measurement }, mynotes={UNREAD}, } @ARTICLE{QuatieriDec78, title={ Short-time spectral analysis with the conventional and sliding CZT }, journal={IEEE Transactions on Acoustics, Speech and Signal Processing}, volume={ASSP-26}, number={6}, year={1978}, month={Dec}, pages={561-6}, abstract={ Two sequential short-time spectral analysis techniques, amenable to nonrecursive filter implementation, are the conventional chirp-z-transform (CZT) realization of the discrete Fourier transform and the sliding CZT realization of the discrete sliding Fourier transform. This paper presents a comparative study of frame rate limitations, windowing, time and frequency resolution, spectral correlation, complexity, and inverse structures for these methods, with particular emphasis on the recently proposed sliding transform. The sliding transform and its CZT realization are viewed as skewed output samples of a filter bank, an approach which aids in understanding the relationship between the conventional and sliding schemes. Numerous forward and inverse CZT formulations are presented to improve resolution, frame rates, and compactness }, keywords={ Fourier transforms spectral analysis Z transforms discrete Fourier transform CZT realization discrete sliding Fourier transform frame rate limitations windowing frequency resolution spectral correlation complexity inverse structures signal processing short time spectral analysis chirp z-transform }, mynotes={UNREAD}, } @CONFERENCE{Otto76, title={ The chirp transform signal processor }, booktitle={1976 Ultrasonics Symposium Proceedings}, volume={}, number={}, year={1976}, month={}, pages={365-70}, abstract={ A unified approach to the design of surface wave implemented chirp transform (CT) processors is presented. The basic chirp transform is analysed, taking into account the finite duration and finite bandwidth of the filters and waveforms involved. The sliding Fourier transform configuration is shown to be inadequate for the analysis of general signals. A simple expression for the transform loss of an arbitrary input signal provides the basis for signal-to-noise analysis of various types of CT processors. An important parameter called fidelity range which characterises CT signal processing capacity is defined. A computer program developed for the simulation of CT processors is described, and results are presented for simulated microscan receiver and chirp transform correlator applications }, keywords={ acoustic surface wave devices digital simulation electronic engineering computing Fourier transforms signal processing chirp transform signal processor sliding Fourier transform fidelity range computer program simulation SAW device }, mynotes={UNREAD}, } @ARTICLE{NuddJan76, author={Nudd, G.R. and Otto, O.W.}, title={ Real-time Fourier analysis of spread spectrum signals using surface-wave-implemented chirp-Z transformation }, journal={IEEE Transactions on Microwave Theory and Techniques}, volume={MTT-24}, number={1}, year={1976}, month={Jan}, pages={54-6}, abstract={ In many communication and radar applications it is desirable to determine the spectral content of signals in real time. A technique employing dispersive surface acoustic wave devices to implement the chirp-Z transform is described. The experimental results obtained for a number of commonly used signals, including the maximal-length pseudonoise sequences, are shown, and the agreement with theoretical prediction is discussed }, keywords={ acoustic surface wave devices Fourier analysis spread spectrum signals real time Fourier analysis surface wave implemented chirp Z transform }, mynotes={UNREAD}, } @ARTICLE{RabinerJun69, author={Rabiner, L.R. and Schafer, R.W. and Rader, C.M.}, title={ The chirp z-transform algorithm }, journal={IEEE Transactions on Audio and Electroacoustics}, volume={au-17}, number={2}, year={1969}, month={Jun}, pages={86-92}, abstract={ A computational algorithm for numerically evaluating the z-transform of a sequence of N samples is discussed. This algorithm has been named the chirp z-transform (CZT) algorithm. Using the CZT algorithm cone can efficiently evaluate the z-transform at M points in the z-plane which lie on circular or spiral contours beginning at any arbitrary point in the z-plane. The angular spacing of the points is an arbitrary constant, and M and N are arbitrary integers. The algorithm is based on the fact that the values of the z-transform on a circular or spiral contour can be expressed as a discrete convolution. Thus one can use well-known high-speed convolution techniques to evaluate the transform efficiently. For M and N moderately large, the computation time is roughly proportional to (N+M) log/sub 2/(N+M) as opposed to being proportional to N.M for direct evaluation of the z-transform at M points }, keywords={ subroutines Z transforms }, mynotes={UNREAD}, } @ARTICLE{ReeveDec76, author={Reeve, C.D. and Rycroft, M.J.}, title={ Unducted VLF energy from tropical lightning as a possible source of mid-latitude VLF emissions and electron precipitation }, journal={Journal of Geophysical Research}, volume={81}, number={34}, year={1976}, month={Dec}, pages={6201-2}, abstract={ The model of Reeve and Rycroft (1976) for the generation of whistler precursors is shown to be a special case of a mechanism by which energy from tropical lightning may be directed into the plasmasphere so as to be able to resonate with energetic electrons just inside the plasmapause. The results of such a wave-particle interaction would be (1) to trigger VLF emissions which may under certain conditions be received on the ground as apparently spontaneous emissions and (2) to reduce the pitch angle of the resonant electrons, causing them to be precipitated into the atmosphere at the foot of the field line just inside the plasmapause. Such precipitating electrons could significantly contribute, by secondary ionization, to the maintenance of the bottom side ionosphere at night }, keywords={ atmospheric electron precipitation ionospheric electromagnetic wave propagation lightning magnetosphere tropical lightning electron precipitation whistler precursors plasmasphere plasmapause trigger VLF emissions resonant electrons bottom side ionosphere unducted VLF energy midlatitude VLF emissions wave particle interactions ionosphere }, mynotes={UNREAD}, } @ARTICLE{HelliwellMay74, title={ Controlled VLF wave injection experiments in the magnetosphere }, journal={Space Science Reviews}, volume={15}, number={6}, year={1974}, month={May}, pages={781-802}, abstract={ Whistler-mode waves injected into the magnetosphere from ground sources (e.g., lightning discharge, v.l.f. transmitters) are used to probe the distribution of ions and electrons in the magnetosphere. They also cause wave growth (v.l.f. emissions) and precipitation of electrons. Bursts of X-rays (>30 keV) and enhancements of D-region ionization are examples of precipitation effects caused by lightning-generated waves. Growing narrowband wave trains are triggered by manmade coherent waves. Growth rates of approximately 100 dB s/sup -1/ and total growths up to 30 dB have been measured using 5.5 kHz signals transmitted from Siple Station, Antarctica. Power line harmonic radiation may suppress triggered emissions or change their frequency-time slope. Exponential growth of narrowband emissions is explained in terms of cyclotron resonance between the waves and trapped energetic electrons, with feedback included. Applications of wave injection experiments include: (1) study of emission mechanisms (2) control of energetic particle precipitation (3) diagnostics of cold and hot plasma, and (4) v.l.f. communications }, keywords={ atmospheric electron precipitation geophysical techniques ion density magnetosphere radiowave propagation whistlers magnetosphere distribution of ions wave growth narrowband wave trains triggered emissions cyclotron resonance whistler mode waves distribution of electrons contoured VLF wave injection D region ionisation X-ray bursts power line harmonic radiation frequency time slope }, mynotes={UNREAD}, } @ARTICLE{AbelFeb98, author={Abel, B. and Thorne, R.M.}, title={ Electron scattering loss in Earth's inner magnetosphere. 2. Sensitivity to model parameters }, journal={Journal of Geophysical Research}, volume={103}, number={A2}, year={1998}, month={Feb}, pages={2397-407}, abstract={ The sensitivity of the rate of energetic electron pitch angle scattering and precipitation loss in the Earth's magnetosphere due to Coulomb interactions with thermal plasma and resonant wave-particle interactions with plasmaspheric hiss, lightning-generated whistlers and VLF transmitter signals is computed for a realistic range of plasma and wave parameters. The computed scattering rates are most sensitive to the choice of mean wave frequency and the average angle of propagation; the frequency bandwidth and angular spread in propagation direction are relatively unimportant. Variations in plasma density can also strongly modulate the effectiveness of wave-particle interactions. The average intensity of plasma waves controls electron lifetimes, but has little effect on the shape of the equilibrium pitch angle distribution function. All three classes of waves must be included together with Coulomb collisions in any realistic analysis of inner magnetospheric electron scattering. The long-term energetic electron population beyond the inner belt is largely controlled by plasmaspheric hiss and, to a lesser extent by lightning-generated whistlers, while VLF transmitter signals constitute the principal loss mechanism over the range 1.3or=40 keV), introduced by interactions with lightning-generated whistler mode waves has been observed to cause phase and amplitude perturbations on subionospheric VLF signals ('Trimpi' events). With a knowledge of the propagation characteristics of the subionospheric signal, analysis of the perturbation details can lead to estimates of the energy, extent, and location of the precipitation. Trimpi events have been observed on VLF signals propagating at high latitudes (L>or=4) over Antarctica, on 3.79-kHz signals transmitted from the horizontal dipole at Siple station. A mode theory computer model for propagation of VLF in the Antarctic Earth-ionosphere waveguide is used to illustrate the characteristics of 3.79-kHz signals as they propagate from Siple toward VLF receivers at Halley and South Pole stations }, keywords={ atmospheric electron precipitation ionospheric electromagnetic wave propagation VLF signal propagation radiowave Trimpi event electron precipitation wave particle interaction burst particle precipitation Antarctic Earth-ionosphere waveguide lightning-generated whistler mode waves subionospheric Antarctica mode theory computer model 3.79 kHz }, mynotes={UNREAD}, } @ARTICLE{OhtaMay91, author={Ohta, K. and Hayakawa, M. and Shimakura, S. and Tomomatsu, T.}, title={ Correlation of whistlers at a low latitude with causative lightnings at conjugate regions }, journal={Transactions of the Institute of Electronics, Information and CommunicationEngineers B-II}, volume={J74B-II}, number={5}, year={1991}, month={May}, pages={276-84}, abstract={ The correlation of occurrence rate of whistlers in January during one solar cycle (1977-87) at low latitude Yamaoka (geomag. lat. 25 degrees N) with thunderstorm activity near its conjugate region and also with solar activity have been investigated. It is found that the occurrence rate has no correlation with the lightning flashes near the conjugate point, while it is negatively correlated with solar activity. On the basis of these findings it is suggested that the ionospheric absorption is of major importance in the long-term variation of whistler occurrence rate at low latitude, and the duct formation is of secondary effect, while the lightning activity is the only necessary condition for whistler occurrence }, keywords={ ionospheric electromagnetic wave propagation lightning magnetospheric electromagnetic wave propagation whistlers whistler occurrence rate VLF low latitude lightnings conjugate regions January 1977-87 Yamaoka thunderstorm activity solar activity ionospheric absorption }, mynotes={UNREAD}, } @ARTICLE{TomomatsuOct90, author={Tomomatsu, T. and Ota, K. and Hayakawa, M. and Shimakura, S. and Eguchi, H.}, title={ Direction findings of whistlers and causative lightnings at conjugate regions }, journal={Memoirs of College of Engineering, Chubu University}, volume={26}, number={}, year={1990}, month={Oct}, pages={83-9}, abstract={ The source and propagation effect of whistlers is the most fundamental subject in whistler studies since the beginning of whistler research. The authors analyse the directional finding of whistlers and causative lightning discharges from the data observed at very low latitudes in China in 1988. On the basis of these directional findings, it is suggested that a propagation mechanism in the ionosphere and magnetosphere with the duct formation is of major importance, while the lightning activity is only a necessary condition for whistler occurrence }, keywords={ ionospheric electromagnetic wave propagation lightning magnetospheric electromagnetic wave propagation whistlers whistlers conjugate regions directional finding causative lightning discharges propagation mechanism ionosphere magnetosphere duct formation }, mynotes={UNREAD}, } @ARTICLE{OhtaMar90, author={Ohta, K. and Hayakawa, M.}, title={ The correlation of whistler occurrence rate at a low latitude with thunderstorm activity at its conjugate region and with solar activity }, journal={Pure and Applied Geophysics}, volume={133}, number={1}, year={1990}, month={Mar}, pages={167-78}, abstract={ The correlations of the occurrence rate of whistlers in January during one solar cycle (1977-1987) at a low latitude station (Yamaoka, geomag. lat. 25 degrees , L=1.26) with thunderstorm activity near its conjugate region and also with solar activity have been investigated; and it is found that the occurrence rate has no correlation with the lightning flashes near the conjugate point, while it is negatively correlated with solar activity. On the basis of these findings it is suggested that the ionospheric absorption is of major importance in the long-term variation of whistler occurrence rate, with the duct formation being of secondary importance, while the lightning activity is only a necessary condition for whistler occurrence }, keywords={ electromagnetic wave absorption ionospheric electromagnetic wave propagation lightning meteorology solar-terrestrial relationships thunderstorms whistlers solar cycle 21 low-latitude whistlers N Australia AD 1977 to 1987 magnetosphere duct formation Japan solar-terrestrial relationships ionosphere EM wave propagation geomagnetic latitude 25 degrees N whistler occurrence rate thunderstorm activity conjugate region solar activity January low latitude station Yamaoka lightning flashes ionospheric absorption long-term variation lightning activity }, mynotes={UNREAD}, } @CONFERENCE{Zhou-Huai-Bei89, author={Zhou Huai-Bei, Sun Chuan-Li and Xiao Zuo}, title={ Remote sensing lightning parameters from whistler spectrum }, booktitle={ISAP Japan 1989. Proceedings of the 1989 International Symposium onAntennas and Propagation}, volume={}, number={}, year={1989}, month={}, pages={1093-6 vol.4}, abstract={ By analysing the spectrum structure parameters of received whistlers, one may sense remotely the characteristic parameter of lightning sources. The system used consists of a minicomputer and a Sonagram with bandwidth zero to 32 kHz. An RLC series equivalent circuit for cloud-to-earth discharge is considered and the inferred values of its parameters are shown to agree with the results of observations }, keywords={ atmospheric techniques equivalent circuits lightning remote sensing spectral analysis whistlers remote sensing VLF whistler spectrum lightning sources minicomputer Sonagram RLC series equivalent circuit cloud-to-earth discharge 32 kHz }, mynotes={UNREAD}, } @ARTICLE{LiaoSep89, author={Liao, C.P. and Freidberg, J.P. and Lee, M.C.}, title={ Explosive spread F caused by lightning-induced electromagnetic effects }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={51}, number={9-10}, year={1989}, month={Sep}, pages={751-8}, abstract={ Lightning-produced electromagnetic effects may produce significant modifications in ionospheric plasmas. An outstanding phenomenon is the so-called 'explosive spread F', whose close link with lightning has been identified (R.F. Woodman and E. Kudeki, 1984, Geophys. Res. Lett. 11, 1165). The parametric instability excited by the lightning-induced whistler waves is proposed as a potential source mechanism causing the explosive spread F. Some observed striking features of this phenomenon can be reasonably explained by the proposed mechanism }, keywords={ F-region ionospheric electromagnetic wave propagation lightning plasma plasma instability whistlers ionospheric disturbances plasma instability F-region plasma density irregularities VLF whistlers transient electric field irregularity scale length threshold field intensity metre-scale irregularities lightning-induced electromagnetic effects ionospheric plasmas explosive spread F lightning-induced whistler waves 2.89 to 2.93 kHz 2 to 8 m 200 to 400 km }, mynotes={UNREAD}, } @ARTICLE{ReeveDec76, author={Reeve, C.D. and Rycroft, M.J.}, title={ Unducted VLF energy from tropical lightning as a possible source of mid-latitude VLF emissions and electron precipitation }, journal={Journal of Geophysical Research}, volume={81}, number={34}, year={1976}, month={Dec}, pages={6201-2}, abstract={ The model of Reeve and Rycroft (1976) for the generation of whistler precursors is shown to be a special case of a mechanism by which energy from tropical lightning may be directed into the plasmasphere so as to be able to resonate with energetic electrons just inside the plasmapause. The results of such a wave-particle interaction would be (1) to trigger VLF emissions which may under certain conditions be received on the ground as apparently spontaneous emissions and (2) to reduce the pitch angle of the resonant electrons, causing them to be precipitated into the atmosphere at the foot of the field line just inside the plasmapause. Such precipitating electrons could significantly contribute, by secondary ionization, to the maintenance of the bottom side ionosphere at night }, keywords={ atmospheric electron precipitation ionospheric electromagnetic wave propagation lightning magnetosphere tropical lightning electron precipitation whistler precursors plasmasphere plasmapause trigger VLF emissions resonant electrons bottom side ionosphere unducted VLF energy midlatitude VLF emissions wave particle interactions ionosphere }, mynotes={UNREAD}, } @ARTICLE{HelliwellMay74, title={ Controlled VLF wave injection experiments in the magnetosphere }, journal={Space Science Reviews}, volume={15}, number={6}, year={1974}, month={May}, pages={781-802}, abstract={ Whistler-mode waves injected into the magnetosphere from ground sources (e.g., lightning discharge, v.l.f. transmitters) are used to probe the distribution of ions and electrons in the magnetosphere. They also cause wave growth (v.l.f. emissions) and precipitation of electrons. Bursts of X-rays (>30 keV) and enhancements of D-region ionization are examples of precipitation effects caused by lightning-generated waves. Growing narrowband wave trains are triggered by manmade coherent waves. Growth rates of approximately 100 dB s/sup -1/ and total growths up to 30 dB have been measured using 5.5 kHz signals transmitted from Siple Station, Antarctica. Power line harmonic radiation may suppress triggered emissions or change their frequency-time slope. Exponential growth of narrowband emissions is explained in terms of cyclotron resonance between the waves and trapped energetic electrons, with feedback included. Applications of wave injection experiments include: (1) study of emission mechanisms (2) control of energetic particle precipitation (3) diagnostics of cold and hot plasma, and (4) v.l.f. communications }, keywords={ atmospheric electron precipitation geophysical techniques ion density magnetosphere radiowave propagation whistlers magnetosphere distribution of ions wave growth narrowband wave trains triggered emissions cyclotron resonance whistler mode waves distribution of electrons contoured VLF wave injection D region ionisation X-ray bursts power line harmonic radiation frequency time slope }, mynotes={UNREAD}, } @ARTICLE{AbelFeb98, author={Abel, B. and Thorne, R.M.}, title={ Electron scattering loss in Earth's inner magnetosphere. 2. Sensitivity to model parameters }, journal={Journal of Geophysical Research}, volume={103}, number={A2}, year={1998}, month={Feb}, pages={2397-407}, abstract={ The sensitivity of the rate of energetic electron pitch angle scattering and precipitation loss in the Earth's magnetosphere due to Coulomb interactions with thermal plasma and resonant wave-particle interactions with plasmaspheric hiss, lightning-generated whistlers and VLF transmitter signals is computed for a realistic range of plasma and wave parameters. The computed scattering rates are most sensitive to the choice of mean wave frequency and the average angle of propagation; the frequency bandwidth and angular spread in propagation direction are relatively unimportant. Variations in plasma density can also strongly modulate the effectiveness of wave-particle interactions. The average intensity of plasma waves controls electron lifetimes, but has little effect on the shape of the equilibrium pitch angle distribution function. All three classes of waves must be included together with Coulomb collisions in any realistic analysis of inner magnetospheric electron scattering. The long-term energetic electron population beyond the inner belt is largely controlled by plasmaspheric hiss and, to a lesser extent by lightning-generated whistlers, while VLF transmitter signals constitute the principal loss mechanism over the range 1.3or=40 keV), introduced by interactions with lightning-generated whistler mode waves has been observed to cause phase and amplitude perturbations on subionospheric VLF signals ('Trimpi' events). With a knowledge of the propagation characteristics of the subionospheric signal, analysis of the perturbation details can lead to estimates of the energy, extent, and location of the precipitation. Trimpi events have been observed on VLF signals propagating at high latitudes (L>or=4) over Antarctica, on 3.79-kHz signals transmitted from the horizontal dipole at Siple station. A mode theory computer model for propagation of VLF in the Antarctic Earth-ionosphere waveguide is used to illustrate the characteristics of 3.79-kHz signals as they propagate from Siple toward VLF receivers at Halley and South Pole stations }, keywords={ atmospheric electron precipitation ionospheric electromagnetic wave propagation VLF signal propagation radiowave Trimpi event electron precipitation wave particle interaction burst particle precipitation Antarctic Earth-ionosphere waveguide lightning-generated whistler mode waves subionospheric Antarctica mode theory computer model 3.79 kHz }, mynotes={UNREAD}, } @ARTICLE{OhtaMay91, author={Ohta, K. and Hayakawa, M. and Shimakura, S. and Tomomatsu, T.}, title={ Correlation of whistlers at a low latitude with causative lightnings at conjugate regions }, journal={Transactions of the Institute of Electronics, Information and CommunicationEngineers B-II}, volume={J74B-II}, number={5}, year={1991}, month={May}, pages={276-84}, abstract={ The correlation of occurrence rate of whistlers in January during one solar cycle (1977-87) at low latitude Yamaoka (geomag. lat. 25 degrees N) with thunderstorm activity near its conjugate region and also with solar activity have been investigated. It is found that the occurrence rate has no correlation with the lightning flashes near the conjugate point, while it is negatively correlated with solar activity. On the basis of these findings it is suggested that the ionospheric absorption is of major importance in the long-term variation of whistler occurrence rate at low latitude, and the duct formation is of secondary effect, while the lightning activity is the only necessary condition for whistler occurrence }, keywords={ ionospheric electromagnetic wave propagation lightning magnetospheric electromagnetic wave propagation whistlers whistler occurrence rate VLF low latitude lightnings conjugate regions January 1977-87 Yamaoka thunderstorm activity solar activity ionospheric absorption }, mynotes={UNREAD}, } @ARTICLE{TomomatsuOct90, author={Tomomatsu, T. and Ota, K. and Hayakawa, M. and Shimakura, S. and Eguchi, H.}, title={ Direction findings of whistlers and causative lightnings at conjugate regions }, journal={Memoirs of College of Engineering, Chubu University}, volume={26}, number={}, year={1990}, month={Oct}, pages={83-9}, abstract={ The source and propagation effect of whistlers is the most fundamental subject in whistler studies since the beginning of whistler research. The authors analyse the directional finding of whistlers and causative lightning discharges from the data observed at very low latitudes in China in 1988. On the basis of these directional findings, it is suggested that a propagation mechanism in the ionosphere and magnetosphere with the duct formation is of major importance, while the lightning activity is only a necessary condition for whistler occurrence }, keywords={ ionospheric electromagnetic wave propagation lightning magnetospheric electromagnetic wave propagation whistlers whistlers conjugate regions directional finding causative lightning discharges propagation mechanism ionosphere magnetosphere duct formation }, mynotes={UNREAD}, } @ARTICLE{OhtaMar90, author={Ohta, K. and Hayakawa, M.}, title={ The correlation of whistler occurrence rate at a low latitude with thunderstorm activity at its conjugate region and with solar activity }, journal={Pure and Applied Geophysics}, volume={133}, number={1}, year={1990}, month={Mar}, pages={167-78}, abstract={ The correlations of the occurrence rate of whistlers in January during one solar cycle (1977-1987) at a low latitude station (Yamaoka, geomag. lat. 25 degrees , L=1.26) with thunderstorm activity near its conjugate region and also with solar activity have been investigated; and it is found that the occurrence rate has no correlation with the lightning flashes near the conjugate point, while it is negatively correlated with solar activity. On the basis of these findings it is suggested that the ionospheric absorption is of major importance in the long-term variation of whistler occurrence rate, with the duct formation being of secondary importance, while the lightning activity is only a necessary condition for whistler occurrence }, keywords={ electromagnetic wave absorption ionospheric electromagnetic wave propagation lightning meteorology solar-terrestrial relationships thunderstorms whistlers solar cycle 21 low-latitude whistlers N Australia AD 1977 to 1987 magnetosphere duct formation Japan solar-terrestrial relationships ionosphere EM wave propagation geomagnetic latitude 25 degrees N whistler occurrence rate thunderstorm activity conjugate region solar activity January low latitude station Yamaoka lightning flashes ionospheric absorption long-term variation lightning activity }, mynotes={UNREAD}, } @CONFERENCE{Zhou-Huai-Bei89, author={Zhou Huai-Bei, Sun Chuan-Li and Xiao Zuo}, title={ Remote sensing lightning parameters from whistler spectrum }, booktitle={ISAP Japan 1989. Proceedings of the 1989 International Symposium onAntennas and Propagation}, volume={}, number={}, year={1989}, month={}, pages={1093-6 vol.4}, abstract={ By analysing the spectrum structure parameters of received whistlers, one may sense remotely the characteristic parameter of lightning sources. The system used consists of a minicomputer and a Sonagram with bandwidth zero to 32 kHz. An RLC series equivalent circuit for cloud-to-earth discharge is considered and the inferred values of its parameters are shown to agree with the results of observations }, keywords={ atmospheric techniques equivalent circuits lightning remote sensing spectral analysis whistlers remote sensing VLF whistler spectrum lightning sources minicomputer Sonagram RLC series equivalent circuit cloud-to-earth discharge 32 kHz }, mynotes={UNREAD}, } @ARTICLE{LiaoSep89, author={Liao, C.P. and Freidberg, J.P. and Lee, M.C.}, title={ Explosive spread F caused by lightning-induced electromagnetic effects }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={51}, number={9-10}, year={1989}, month={Sep}, pages={751-8}, abstract={ Lightning-produced electromagnetic effects may produce significant modifications in ionospheric plasmas. An outstanding phenomenon is the so-called 'explosive spread F', whose close link with lightning has been identified (R.F. Woodman and E. Kudeki, 1984, Geophys. Res. Lett. 11, 1165). The parametric instability excited by the lightning-induced whistler waves is proposed as a potential source mechanism causing the explosive spread F. Some observed striking features of this phenomenon can be reasonably explained by the proposed mechanism }, keywords={ F-region ionospheric electromagnetic wave propagation lightning plasma plasma instability whistlers ionospheric disturbances plasma instability F-region plasma density irregularities VLF whistlers transient electric field irregularity scale length threshold field intensity metre-scale irregularities lightning-induced electromagnetic effects ionospheric plasmas explosive spread F lightning-induced whistler waves 2.89 to 2.93 kHz 2 to 8 m 200 to 400 km }, mynotes={UNREAD}, } @ARTICLE{RobinsonSep89, author={Robinson, R.M. and Winningham, J.D. and Sharber, J.R. and Burch, J.L. and Heelis, R.}, title={ Plasma and field properties of suprathermal electron bursts }, journal={Journal of Geophysical Research}, volume={94}, number={A9}, year={1989}, month={Sep}, pages={12031-6}, abstract={ The authors show plasma and field observations made by instruments on the Dynamics Explorer satellites during a suprathermal burst event on October 8, 1981. They begin with a brief review of the properties of suprathermal bursts as determined in previous studies. They then show the Dynamics Explorer data for the suprathermal burst event studied. The correlation between the bursts and low-frequency electric field wave power suggests that the electrons in the bursts are produced by interaction with waves. The authors suggest that the waves are generated in regions of strong upward current and propagate perpendicular to the field line to produce accelerated electrons outside the region of wave generation. This mechanism accounts for the correlation of bursts with wave power as well as the distinctive spatial distribution of suprathermal bursts }, keywords={ atmospheric electricity atmospheric electron precipitation magnetosphere plasma atmosphere magnetosphere electron precipitation AD 1981 10 08 propagation field properties suprathermal electron bursts plasma Dynamics Explorer electric field wave power interaction strong upward current accelerated electrons region of wave generation spatial distribution }, mynotes={UNREAD}, } @ARTICLE{ImhofMay87, author={Imhof, W.L. and Voss, H.D. and Mobilia, J. and Gaines, E.E. and Evans, D.S.}, title={ Electron precipitation burst in the nighttime slot region measured simultaneously from two satellites }, journal={Journal of Geophysical Research}, volume={92}, number={A5}, year={1987}, month={May}, pages={4515-24}, abstract={ Based on data acquired in 1982 with the Stimulated Emission of Energetic Particles payload on the low-altitude (170-280 km) S81-1 spacecraft and the Space Environment Monitor instrumentation on the NOAA 6 satellite (800-830 km), a study has been made of short-duration nighttime electron precipitation bursts at L=2.0-3.5. From 54 passes of each satellite across the slot region simultaneously in time, 21 bursts were observed on the NOAA 6 spacecraft, and 76 on the S81-1 satellite. Five events, probably associated with lightning, were observed simultaneously from the two spacecraft within 1.2 s, providing a measure of the spatial extent of the bursts. This limited sample indicates that the intensity of precipitation events falls off with width in longitude and L shell but individual events extend as much as 5 degrees in invariant latitude and 43 degrees in longitude. Further characteristics of the electron precipitation are presented }, keywords={ atmospheric electron precipitation magnetosphere radiation belts ionosphere electron precipitation burst radiation belt loss rate AD 1982 magnetosphere nighttime slot region short-duration lightning }, mynotes={UNREAD}, } @ARTICLE{GainesJan95, author={Gaines, E.E. and Chenette, D.L. and Imhof, W.L. and Jackman, H. and Winningham, J.D.}, title={ Relativistic electron fluxes in May 1992 and their effect on the middle atmosphere }, journal={Journal of Geophysical Research}, volume={100}, number={D1}, year={1995}, month={Jan}, pages={1027-33}, abstract={ Enhancements in the fluxes of relativistic electrons trapped within the Earth's magnetosphere have been measured by the high-energy particle spectrometer, part of the particle environment monitor on the upper atmosphere research satellite (UARS). The largest increase in the electron fluxes with energies greater than 1 MeV observed on UARS from October 1991 through July 1994 was in early May 1992. The fluxes of trapped electrons in the drift loss cone and locally precipitating electrons showed differing buildup and decay rates as a function of invariant latitude. Increases of more than 2 orders of magnitude were observed in drift loss cone fluxes at magnetic latitudes of 40 degrees -66 degrees and in precipitating fluxes from 48 degrees to 66 degrees . The energy flux contained in the most intense local precipitation observed was approximately 0.1 erg cm/sup -2/ s/sup -1/ entering the atmosphere and creating up to 1000 ion pairs cm/sup -3/ s/sup -1/ at 55-km altitude. The daily averaged energy flux from directly precipitating electrons with energies >1 MeV deposited >10/sup 20/erg d/sup -1/ worldwide into the atmosphere for the period May 12-21, 1992, producing odd nitrogen molecules below 60-km altitude }, keywords={ atmospheric electron precipitation atmospheric ionisation ionosphere magnetosphere mesosphere magnetosphere trapped particles relativistic electron flux middle atmosphere mesosphere high-energy particle trapped electrons drift loss cone electron precipitation neutral atmosphere AD 1992 05 ionosphere 0.1 to 10 MeV }, mynotes={UNREAD}, } @ARTICLE{WinninghamJun93, author={Winningham, J.D. and Sharber, J.R. and Frahm, R.A. and Burch, J.L. and Faker, N. and Black, R.K. and Blevins, V.A. and Andrews, J.P. and Rudzki, J. and Sablik, M.J. and Chenette, D.L. and Datlowe, D.W. and Gaines, E.E. and Imhof, W.I. and Nightingale, R.W. and Reagan, J.B. and Robinson, R.M. and Schumaker, T.L. and Shelley, E.G. and Vondrak, R.R. and Voss, H.D. and Bythrow, P.F. and Anderson, B.J. and Potemra, T.A. and Zanetti, L.J. and Holland, D.B. and Rees, M.H. and Lummerzheim, D. and Reid, G.C. and Roble, R.G. and Clauer, C.R. and Banks, P.M.}, title={ The UARS particle environment monitor }, journal={Journal of Geophysical Research}, volume={98}, number={D6}, year={1993}, month={Jun}, pages={10649-66}, abstract={ The overall objective of the particle environment monitor (PEM) is to provide comprehensive measurements of both local and global energy inputs into the Earth's atmosphere by charged particles and Joule dissipation using a carefully integrated set of instruments. PEM consists of four instruments: the atmospheric X-ray imaging spectrometer (AXIS), the high-energy particle spectrometer (HEPS), the medium-energy particle spectrometer (MEPS), and the vector magnetometer (VMAG). AXIS provides global scale images and energy spectra of 3- to 100-keV bremsstrahlung X-rays produced by electron precipitation into the atmosphere. HEPS and MEPS provide in situ measurements of precipitating electrons in the energy range from 1 eV to 5 MeV and protons in the energy range from 1 eV to 150 MeV. Particles in this energy range deposit their energy in the atmosphere at altitudes extending from several hundred kilometers down to as low as approximately 30 km }, keywords={ atmospheric electron precipitation atmospheric proton precipitation atmospheric techniques ionospheric techniques UARS Upper Atmosphere Research Satellite measurement technique satellite remote sensing instrumentation equipment AXIS particle precipitation ionosphere upper atmosphere particle environment monitor charged particles Joule dissipation X-ray imaging spectrometer high-energy particle spectrometer medium-energy particle spectrometer vector magnetometer electron precipitation 1 eV to 150 MeV }, mynotes={UNREAD}, } @ARTICLE{ImhofAug93, author={Imhof, W.L. and Gaines, E.E.}, title={ Inputs to the atmosphere from relativistic electrons }, journal={Journal of Geophysical Research}, volume={98}, number={A8}, year={1993}, month={Aug}, pages={13575-80}, abstract={ The precipitation rates into the atmosphere of electrons >1 MeV during a weak relativistic enhancement in the spring of 1979 have been derived from electron fluxes measured on a low-altitude satellite, P78-1. The inputs to the atmosphere were obtained from drift loss cone fluxes of electrons >1 MeV by using measurements with fine angular resolution at lower energies of the ratios of the direct precipitation rates to the fluxes of locally trapped electrons. The analyses indicated that often the inputs to the atmosphere may be primarily from precipitating electrons at pitch angles near the edge of the trapped fluxes, illustrating the inadequacy of broad angular resolution measurements for precipitation studies. The data showed a strong L dependence for the precipitation of relativistic electrons extending from L approximately=2.5 to L approximately=8.5, indicating the limitations of obtaining inputs to the atmosphere from high-altitude measurements alone over a limited L shell range, such as at geosynchronous altitude (L approximately=6.6). When summed over all longitudes and latitudes in the southern hemisphere, the total input energy rate of electrons >1 MeV precipitating into the atmosphere near the peak of the event on May 25-30, 1979, was approximately 5 * 10/sup 19/ ergs d/sup -1/ }, keywords={ atmospheric electron precipitation atmosphere relativistic electron precipitation rate relativistic enhancement spring P78-1 drift loss cone fluxes locally trapped electrons pitch angles trapped fluxes broad angular resolution measurements L dependence total input energy rate Northern Hemisphere AD 1979 05 25 to 30 1 MeV }, mynotes={UNREAD}, } @ARTICLE{ImhofSep92, author={Imhof, W.L. and Voss, H.D. and Mobilia, J. and Datlowe, D.W. and Gaines, E.E. and McGlennon, J.P. and Inan, U.S.}, title={ Relativistic electron microbursts }, journal={Journal of Geophysical Research}, volume={97}, number={A9}, year={1992}, month={Sep}, pages={13829-37}, abstract={ The authors report the first satellite observations of relativistic (>1 MeV) electron precipitation in microbursts with measured durations of less than 1 s. The data on these relativistic microbursts appear to indicate that many of the bursts may be due to wave-particle interaction not with whistler mode chorus but possibly with other waveforms. The locations of many of the relativistic microbursts are concentrated at the outer edge of the trapped radiation belt, where the gyroradii of the electrons are comparable to the curvature of the magnetic field lines and stable trapping may therefore not occur. The preferred location of the microbursts, which may be primarily spatial in character, implies the possible importance of irregularities in the magnetic field lines near the trapping boundary as the responsible mechanism }, keywords={ atmospheric electron precipitation radiation belts magnetosphere atmosphere electron microbursts relativistic microbursts wave-particle interaction trapped radiation belt gyroradii 1 MeV }, mynotes={UNREAD}, } @ARTICLE{Laquer92, author={Laquer, H.L. and Gaines, J.R. and Jr., Brainard and S., Hutson and S.D., Pisanelli and J., Cooke and D.W., Gray and E.R., Ott and K.C., Peterson and E.J., Smith and J.F., Balachandran and U., Lanagan and M.T., Poeppel and R.B., Wolf and J.D. and Laquer, F.C.}, title={ Preparation and properties of Y-124 superconductor made by a chemical precipitation method }, journal={AIP Conf. Proc. (USA), AIP Conference Proceedings}, volume={}, number={}, year={1992}, month={}, pages={448-55}, abstract={ The authors have prepared the thermodynamically stable YBCO-124 high temperature superconductor in powder form by a chemical precipitation method and have characterized the material by a number of chemical and physical methods, including carbon content, X-ray diffraction, thermogravimetry, scanning electron microscopy, surface area, thermally stimulated luminescence, and the superconducting transition and magnetization curves. They have also started work on consolidating the powders by hot pressing }, keywords={ barium compounds high-temperature superconductors luminescence of inorganic solids magnetisation powders scanning electron microscope examination of materials superconducting transition temperature thermoluminescence X-ray diffraction examination of materials yttrium compounds high temperature superconductor powder form chemical precipitation method X-ray diffraction thermogravimetry scanning electron microscopy surface area thermally stimulated luminescence superconducting transition magnetization curves hot pressing YBa/sub 2/Cu/sub 4/O/sub 8/ }, mynotes={UNREAD}, } @ARTICLE{ImhofApr91, author={Imhof, W.L. and Voss, H.D. and Mobilia, J. and Datlowe, D.W. and Gaines, E.E.}, title={ The precipitation of relativistic electrons near the trapping boundary }, journal={Journal of Geophysical Research}, volume={96}, number={A4}, year={1991}, month={Apr}, pages={5619-29}, abstract={ Presents measurements from the low-altitude three-axis-stabilized satellite S81-1 of trapped and precipitating electrons from 6 keV to above 1 MeV. Significant fluxes of precipitating relativistic electrons above 1 MeV within the bounce loss cone are much more often observed near midnight than noon and generally in narrow spikes <100 km in width typically at L values between 4 and 6 near the radiation belt boundary. A trend was observed for the higher-energy precipitating electron fluxes to peak at somewhat lower L values. The precipitation of >1-MeV electrons has been measured to occur at intensities and in locations that are widely variable within a few minutes superposed on longer-term variations. On one of the days of strongest precipitation the total night time input to the atmosphere during 12 hours from >1-MeV electrons within the bounce loss cone near the trapping boundary was approximately 10/sup 19/ ergs }, keywords={ atmospheric electron precipitation electrons ionosphere magnetosphere radiation belts magnetospheric relativistic electrons precipitation McIlwaine L-shells 4 to 6 trapped electron fluxes precipitating electron spikes widths aeronomy electrons nighttime energy input electron intensity variations AD 1982 05 28 to 12 05 electron flux variations timescales trapping boundary low-altitude three-axis-stabilized satellite precipitating relativistic electrons midnight radiation belt boundary higher-energy precipitating electron fluxes 170 to 280 km 1 TJ 1 MeV 0 to 100 km 0 to 20 s }, mynotes={UNREAD}, } @ARTICLE{ImhofApr90, author={Imhof, W.L. and Mobilia, J. and Datlowe, D.W. and Voss, H.D. and Gaines, E.E.}, title={ Longitude and temporal variations of energetic electron precipitation near the trapping boundary }, journal={Journal of Geophysical Research}, volume={95}, number={A4}, year={1990}, month={Apr}, pages={3829-39}, abstract={ Electron precipitation occurring at latitudes near the midnight trapping boundary was measured remotely with a satellite-borne X-ray imager (>21 keV). This investigation has demonstrated for the first time the repetitive mapping of precipitation at the trapping boundary with X-rays. The satellite spin motion (5.5 second period) provided repeated scans of each scene during a single pass of the satellite. When in in situ electron precipitation, measured directly with a spectrometer (>68 keV) on the same satellite, was limited to a narrow region at the trapping boundary the precipitation inferred from the X-rays was generally fairly uniform over a median longitude interval of at least 45 degrees . Significant decreases of X-rays at longitudes away from the satellite crossing seldom occurred, but significant increases of certain longitudes were sometimes observed. The widespread arc patterns of the precipitation have important implications for both understanding the nature of the responsible loss mechanisms and for assessing the atmospheric effects }, keywords={ atmospheric electron precipitation atmospheric radiation aurora ionosphere magnetosphere radiation belts X-ray aurora electron precipitation repetitive mapping radiation belt outer boundary auroral ionosphere electron precipitation longitudinal distribution aeronomy electron precipitation arc patterns AD 1979 02 to 10 X-ray flux increases temporal variations energetic electron precipitation midnight trapping boundary satellite-borne X-ray imager satellite spin motion in situ electron precipitation median longitude interval 68 keV 21 to 80 keV 563 to 610 km }, mynotes={UNREAD}, } @ARTICLE{ImhofMay87, author={Imhof, W.L. and Voss, H.D. and Mobilia, J. and Gaines, E.E. and Evans, D.S.}, title={ Electron precipitation burst in the nighttime slot region measured simultaneously from two satellites }, journal={Journal of Geophysical Research}, volume={92}, number={A5}, year={1987}, month={May}, pages={4515-24}, abstract={ Based on data acquired in 1982 with the Stimulated Emission of Energetic Particles payload on the low-altitude (170-280 km) S81-1 spacecraft and the Space Environment Monitor instrumentation on the NOAA 6 satellite (800-830 km), a study has been made of short-duration nighttime electron precipitation bursts at L=2.0-3.5. From 54 passes of each satellite across the slot region simultaneously in time, 21 bursts were observed on the NOAA 6 spacecraft, and 76 on the S81-1 satellite. Five events, probably associated with lightning, were observed simultaneously from the two spacecraft within 1.2 s, providing a measure of the spatial extent of the bursts. This limited sample indicates that the intensity of precipitation events falls off with width in longitude and L shell but individual events extend as much as 5 degrees in invariant latitude and 43 degrees in longitude. Further characteristics of the electron precipitation are presented }, keywords={ atmospheric electron precipitation magnetosphere radiation belts ionosphere electron precipitation burst radiation belt loss rate AD 1982 magnetosphere nighttime slot region short-duration lightning }, mynotes={UNREAD}, } @ARTICLE{ImhofMar86, author={Imhof, W.L. and Voss, H.D. and Reagan, J.B. and Datlowe, D.W. and Gaines, E.E. and Mobilia, J. and Evans, D.S.}, title={ Relativistic electron and energetic ion precipitation spikes near the plasmapause }, journal={Journal of Geophysical Research}, volume={91}, number={A3}, year={1986}, month={Mar}, pages={3077-88}, abstract={ An investigation has been made of electron and associated ion precipitation spikes near the plasmapause that are narrow in L shell and in which relativistic electrons are favored. The electron energy spectra during the spikes sometimes had equivalent e fold energies in excess of 500 keV. In approximately 31% of these spike events observed from the low-altitude polar orbiting satellites P72-1, P78-1, and S81-1, nearly simultaneous precipitation was measured in energetic ions above approximately 30 keV at about the same L value. Several of the precipitation spikes occurred primarily in the drift loss cone, but in some cases, significant precipitation was also observed in the bounce loss cone. The electron spikes occurred preferentially in the evening sector and all of the associated narrow ion spikes were in that local time interval. Further observational findings are reported }, keywords={ atmospheric electron precipitation atmospheric precipitation magnetosphere relativistic electron spike magnetosphere electron precipitation ionosphere AD 1972 to 1982 energetic ion precipitation spikes plasmapause electron energy spectra drift loss cone bounce loss cone }, mynotes={UNREAD}, } @ARTICLE{ImhofDec84, author={Imhof, W.L. and Reagan, J.B. and Gaines, E.E. and Datlowe, D.W.}, title={ The L shell region of importance for waves emitted at ground level as a loss mechanism for trapped electrons >68 keV }, journal={Journal of Geophysical Research}, volume={89}, number={A12}, year={1984}, month={Dec}, pages={1/827-35}, abstract={ The objective of this paper is to identify the L shell regions(s) where VLF waves emitted at ground level may play a significant role as a loss mechanism for radiation belt electrons with energies above 68 keV. This assessment is made possible by studying the day-night differences in inner belt electron precipitation and comparing with the much stronger transmission of waves at frequencies of 15-25 kHz through the ionosphere at night and the known higher daytime intensities for waves of natural origin other than lightning. Intensities of electrons trapped on drift shells which dip below sea level in the anomaly are used to study the rates of loss from the radiation belts }, keywords={ atmospheric electron precipitation magnetosphere radiation belts radiowave EM wave trapped particle electron precipitation magnetosphere wave particle interaction L shell region loss mechanism trapped electrons VLF radiation belt inner belt }, mynotes={UNREAD}, } @ARTICLE{VossDec84, author={Voss, H.D. and Imhof, W.L. and Walt, M. and Mobilia, J. and Gaines, E.E. and Reagan, J.B. and Inan, U.S. and Helliwell, R.A. and Carpenter, D.L. and Katsufrakis, J.P. and Chang, H.C.}, title={ Lightning-induced electron precipitation }, journal={Nature}, volume={312}, number={5996}, year={1984}, month={Dec}, pages={740-2}, abstract={ The authors report the first satellite measurements of electron precipitation induced by lightning. The measured energy deposition of these conspicuous lightning-induced electron precipitation (LEP) bursts ( approximately 10/sup -3/ erg cm/sup -2/) is sufficient to deplete the Earth's radiation belts and to alter subionospheric radiowave propagation (21 keV) mappings and direct electron (>68 keV) measurements from the low-altitude polar-orbiting satellite P78-1 were performed at critical times and locations near the onset of a magnetospheric substorm on July 3, 1979 at approximately 2149 UT. The bremsstrahlung X-ray intensities emitted from the atmosphere over a wide range of longitudes and L shells were negligible just before the substorm onset, then rose to a maximum within about a minute or less, and remained at an enhanced level for the next nine minutes. The simultaneous X-ray measurements from the SBARMO-79 balloons and the P78-1 satellite indicate that the electron precipitation started at L=5-5.5 without a significant precipitation from higher L shells. A relatively sharp longitude decrease was observed in electron precipitation at positions east of approximately 30 degrees E or at magnetic local times after approximately 1.5 hours }, keywords={ atmospheric electron precipitation magnetic storms X-rays magnetosphere magnetic storm AD 1979 07 03 electron precipitation bremsstrahlung onset substorm atmosphere electron precipitation }, mynotes={UNREAD}, } @ARTICLE{ImhofJun82, author={Imhof, W.L. and Anderson, R.R. and Reagan, J.B. and Gaines, E.E.}, title={ Coordinated measurements of slot region electron precipitation by plasmaspheric wave bands }, journal={Journal of Geophysical Research}, volume={87}, number={A6}, year={1982}, month={Jun}, pages={4418-26}, abstract={ Simultaneous measurements have been made of the precipitating electron spectra, the wave frequency distributions, and the plasma density profiles. The electron measurements were performed from the P78-1 low-altitude satellite, whereas the wave and plasma density observations were made with the plasma wave experiment on the ISEE 1 spacecraft. Broad bands are often observed in the electron energy spectra with a well-defined low-energy cutoff that decreases in energy with increasing L value in a manner consistent with that calculated for first-order cyclotron resonance with waves at the high-frequency cutoff of the band. Overall, the plasma wave and the electron measurements are consistent with each other, supporting an earlier hypothesis for the precipitation mechanisms (Lyons et al. (1972)) }, keywords={ atmospheric electron precipitation ionosphere plasmasphere energy distribution interaction mechanism slot region electron precipitation wave bands frequency cyclotron resonance cutoff }, mynotes={UNREAD}, } @ARTICLE{ImhofJan80, author={Imhof, W.L. and Reagan, J.B. and Gaines, E.E.}, title={ Measurements of inner zone electron precipitation }, journal={Journal of Geophysical Research}, volume={85}, number={A1}, year={1980}, month={Jan}, pages={9-16}, abstract={ Energetic electron (>or=0.16 MeV) data taken from November 1972 to April 1973 from over 1000 passes of a low-altitude ( approximately 750 km) noon-midnight polar-orbiting satellite across the L=1.75 field line in both the northern and southern hemispheres have been analyzed for evidence of the longitude and local time distributions in electron precipitation on that field line. The precipitation processes were observed to be weak, at least near local noon and midnight, as evidenced from the negligible fluxes observed at all pitch angles when the conjugate point is below sea level and from the absence of any direct observation of electrons at L=1.75 in the bounce loss cone at all longitudes. By observing quasi-trapped fluxes with a spectrometer having a large geometric factor, a high sensitivity was achieved for detecting electron precipitation and measuring the energy spectra with fine resolution }, keywords={ atmospheric electron precipitation magnetosphere radiation belts inner zone electron precipitation L=1.75 field line southern hemisphere local time distributions local noon midnight bounce loss cone low altitude noon midnight polar orbiting satellite energetic electron precipitation AD 1972 11 to 1973 04 precipitation longitude distribution altitude km 0750 quasitrapped electrons fluxes keV 0160 }, mynotes={UNREAD}, } @ARTICLE{ImhofNov79, author={Imhof, W.L. and Reagan, J.B. and Gaines, E.E.}, title={ Studies of the sharply defined L dependent energy threshold for isotropy at the midnight trapping boundary }, journal={Journal of Geophysical Research}, volume={84}, number={A11}, year={1979}, month={Nov}, pages={6371-84}, abstract={ It has previously been reported (Imhog et al., 1977) that near the midnight trapping boundary the onset of isotropy for electrons and protons often occurs at a sharply defined energy threshold which decreases rapidly with increasing L value. This paper describes how the addition of energy spectrum measurements to the pitch angle distributions provides new information on the magnetic field configuration in the tail region during these cases. The energy dependent characteristics presented here include the positions and total latitude widths of the transition region from locally trapped to precipitation pitch angle distributions, the intensities and locations of near-coincident enhancements in the trapped fluxes, and the intensities of electron precipitation at energies below the threshold for isotropy }, keywords={ magnetosphere radiation belts sharply defined L dependent energy threshold midnight trapping boundary magnetic field configuration magnetosphere tail trapped particle magnetosphere trapping boundary geomagnetic disturbance trapped electron trapped proton radiation belt }, mynotes={UNREAD}, } @ARTICLE{ImhofNov77, author={Imhof, W.L. and Gaines, E.E. and Reagan, J.B.}, title={ The time persistence of certain features of electron precipitation in the slot region }, journal={Journal of Geophysical Research}, volume={82}, number={32}, year={1977}, month={Nov}, pages={5024-30}, abstract={ An investigation is made of the short-term persistence of certain features of electron precipitation in the slot region: the total precipitating flux levels and the occurrence of peaks having strongly L-dependent central energies. The latter phenomenon is of special interest, since the peaks have been shown to be consistent with the idea that the responsible mechanism is wave-particle interactions with a narrow frequency band of waves. At a given magnetic local time the equivalent wave frequencies which may be responsible for the peaks are found to have statistically significant correlation coefficients between pairs of passes separated by 100 min or less. The total electron intensities of >130 keV have significant correlation coefficients for separation times of 24 hours or less. These findings are consistent with a significant electron precipitation resulting from a slowly varying hiss band, in preference to a more random occurrence of discrete emissions }, keywords={ atmospheric electron precipitation atmospherics ionosphere magnetosphere electron precipitation slot region electron precipitation total precipitating flux levels magnetic local time equivalent wave frequencies slowly varying hiss band electron spectra peaks central energies L-dependence wave particle interactions 130 keV electrons intensities 1971-089 A satellite plasmasphere ELF hiss precipitation features time persistence ionosphere magnetosphere }, mynotes={UNREAD}, } @ARTICLE{ImhofJan77, author={Imhof, W.L. and Reagan, J.B. and Nakano, G.H. and Gaines, E.E.}, title={ Narrow spikes in the selective precipitation of relativistic electrons at mid-latitudes }, journal={Journal of Geophysical Research}, volume={82}, number={1}, year={1977}, month={Jan}, pages={117-24}, abstract={ Relativistic electron precipitation spikes have been observed in the quasi-trapped population at mid-latitudes (L approximately=3.5-4.5). The spike electrons are not in the local loss cone but precipitate into the atmosphere upon drift in longitude. In these spikes, often as narrow as 0.3 degrees in invariant latitude, the fluxes of electrons >or approximately=4 MeV may undergo pronounced enhancements, whereas the intensities of electrons in the few hundred keV range may not be significantly affected. This energy selectivity in the formation of the spikes is perhaps more suggestive of wave-particle interactions }, keywords={ atmospheric electron precipitation magnetosphere radiation belts precipitation spikes relativistic electrons selective precipitation electron flux outer radiation belt quasitrapped particles magnetosphere midlatitudes wave particle interactions }, mynotes={UNREAD}, } @ARTICLE{ImhofJan76, author={Imhof, W.L. and Gaines, E.E. and Reagan, J.B.}, title={ Local time dependence of the loss of energetic electrons from the slot region of the radiation belts }, journal={Journal of Geophysical Research}, volume={81}, number={1}, year={1976}, month={Jan}, pages={291-3}, abstract={ An investigation has been made of the local time morphology of electron (>130 keV) precipitation from the slot region of the radiation belts. Quasi-trapped electrons (h/sub min/<0) were observed just east of the South Atlantic anomaly at low altitudes ( approximately 800 km) from the satellite 1971-089A. On the average, the fluxes of electrons precipitating in the daytime are greater than those near midnight, consistent with the finding of Vampola et al. (1971). In addition, shortly after 0800 hours MLT there is a pronounced increase in the frequency of occurrence of peaks in the energy spectra. These peaks have central energies that decrease rapidly with increasing L value. The data reveal that the electron loss processes are more effective during the daytime than near midnight and that there may be basic differences in the nature of the precipitation mechanisms at the two times }, keywords={ atmospheric electron precipitation radiation belts slot region radiation belts local time morphology South Atlantic anomaly satellite 1971-089A electron precipitation }, mynotes={UNREAD}, } @ARTICLE{ImhofSep75, author={Imhof, W.L. and Nakano, G.H. and Gaines, E.E. and Reagan, J.B.}, title={ A coordinated two-satellite study of energetic electron precipitation events }, journal={Journal of Geophysical Research}, volume={80}, number={25}, year={1975}, month={Sep}, pages={3622-8}, abstract={ A new technique for studying the spatial/temporal variations of energetic electron precipitation events is investigated. Data are presented in which precipitating electrons were measured simultaneously on two coordinated polar-orbiting satellites and the bremsstrahlung produced by the electrons precipitating into the atmosphere was observed from one of the satellites. With the coordinated data a study is made of events in which large fluctuations were observed in the precipitating energetic electron intensities }, keywords={ atmospheric electron precipitation atmospheric techniques energetic electron precipitation coordinated two satellite technique }, mynotes={UNREAD}, } @ARTICLE{ImhofApr72, author={Imhof, W.L. and Bakke, J.C. and Gaines, E.E. and Reagan, J.B.}, title={ Angular distribution and energy spectrum measurements of energetic electrons precipitating at high latitudes }, journal={Trans. Am. Geophys. Union (USA), Transactions of the American GeophysicalUnion}, volume={53}, number={4}, year={1972}, month={Apr}, pages={499}, abstract={ Electron spectrometers on two different low-altitude polar-orbiting satellites have been providing data on the energy spectra and pitch-angle distributions of electrons in the radiation belts. Measurements of electrons above 0.4 MeV were made during the period March 1969 to August 1970 with a spectrometer on board the satellite OV1-18 at altitudes of approximately 500 km. Data have been acquired since October 1971 with two identical high-resolution spectrometers on the oriented satellite STP 71-2 at altitudes of approximately 800 km. The latter instruments, each with a large geometric factor and an acceptance half-angle of 20 degrees , are placed at angles of 70 degrees with respect to each other. The counting rates of electrons above 0.13 MeV are scaled 32 times each second and the energy spectra measured with a 256-channel pulse-height analyzer. In the outer radiation belt, with both satellite experiments, fluxes are observed at 90 degrees pitch angle on virtually every pass, even when h/sub min/ is less than 100 km. The fluxes of locally trapped electrons are commonly much larger than the fluxes of those in the loss cone, but at times the precipitating fluxes increase by large factors on a very short time scale. The energy and local time dependences of the precipitation phenomena are investigated }, keywords={ atmospheric precipitation radiation belts angular distribution energy spectrum energetic electrons high latitudes radiation belts locally trapped electrons precipitating fluxes energy and local time dependences }, mynotes={UNREAD}, } @ARTICLE{SaitoOct79, author={Saito, T. and Yumoto, K. and Aoyama, I. and Toyama, F. and Takahashi, T.}, title={ Typical mini-substorm and long-period Pi2 event observed by the Jikiken satellite on December 11, 1978 }, journal={Bulletin of the Institute of Space and Aeronautical Science, University ofTokyo B}, volume={15}, number={3B}, year={1979}, month={Oct}, pages={739-50}, abstract={ A typical long-period Pi2 event that was associated with a distinct mini-substorm took place at 1355 UT (2255 in 135 degrees east meridian time) on December 11, 1978, after a successive ten-day magnetically calm period. The event was observed simultaneously at both the Jikiken (Exos-B) satellite near an expanded plasmapause on the 21 h LT meridian and a ground-based station, Onagawa, on the approximately 23 h LT meridian. The plasmapause position before the substorm onset is estimated from the stimulated plasma wave experiment to be L>or approximately=6.3. A dynamic spectrum analysis of the data revealed that the observed main period of the Pi2 was 140 seconds at Jikiken, and both 140 and 220 seconds at Onagawa. The torsional oscillation model (namely, the plasma-sheet model) that an odd mode hydromagnetic torsional oscillation of the contracted dipole-like field-line that was excited by the distant plasma instability on a tail-like field-line is applied to explain the mechanism of the Pi2. The tail-like field-line whose apex was at >16.4 R/sub E/ is assumed to contract rapidly due to the instability to the dipole-like one with the apex at 9.2 R/sub E/. The period of 140 sec of the same Pi2 event observed at Jikiken is interpreted as a transient hydromagnetic surface wave excited secondarily on the with plasmapause. This mechanism is discussed in comparison with the Pg model that a hydromagnetic surface wave on the expanded plasmapause excited by a plasma instability on the plasmapause is observed as a giant pulsation in the auroral zone }, keywords={ artificial satellites geomagnetism ionosphere magnetic storms magnetohydrodynamics magnetosphere micropulsations Jikiken satellite expanded plasmapause 21 h LT meridian Onagawa plasmapause position substorm onset stimulated plasma wave experiment dynamic spectrum analysis odd mode hydromagnetic torsional oscillation distant plasma instability transient hydromagnetic surface wave giant pulsation auroral zone long period Pi 2 pulsation event minisubstorm MHD magnetic storm AD 1978 12 11 micropulsations pulsations main period contracted dipole like field line tail like magnetic field line magnetosphere plasma sheet plasmapause wave EXOS-B }, mynotes={UNREAD}, } @ARTICLE{SaitoDec76, author={Saito, T. and Sakurai, T. and Koyama, Y.}, title={ Mechanism of association Pi2 pulsation and magnetospheric substorm }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={38}, number={12}, year={1976}, month={Dec}, pages={1265-77}, abstract={ Based on the analysis of data obtained at the ground and by satellites, the following morphological characteristics of Pi 2 are revealed: (1) Pi 2 shows a peak amplitude at the auroral oval and a secondary maximum inside the plasmapause latitude, (2) a phase reversal of the NS-component of Pi 2 is exhibited both at the auroral oval and near the plasmapause latitude, (3) Pi 2 occurs associated with a release of the magnetic energy in the magnetotail lobe, (4) Pi 2 propagates in a compressional mode in the magnetosphere and is detected as a torsional mode on the ground. The result obtained leads to a Pi 2 model that the substorm-associated compressional mode of HM waves excited in the magnetotail is converted to the torsional mode of HM waves propagating along the field-line anchoring at the northern and the southern auroral ovals and is observed as magnetic pulsation Pi 2 on the dark hemisphere of the Earth }, keywords={ magnetic storms magnetosphere micropulsations magnetospheric substorm morphological characteristics plasmapause latitude auroral oval magnetotail lobe compressional mode magnetosphere torsional mode Pi 2 pulsation magnetic energy release satellite data ULF waves ground based observations MHD waves }, mynotes={UNREAD}, } @ARTICLE{SaitoNov76, author={Saito, T. and Yumoto, K. and Koyama, Y.}, title={ Magnetic pulsation Pi2 as a sensitive indicator of magnetospheric substorm }, journal={Planetary and Space Science}, volume={25}, number={11}, year={1976}, month={Nov}, pages={1025-9}, abstract={ The identification of substorm onset is quite important in studying the mechanism of excitation of substorm disturbances. At present, one of the most practical methods to identify accurately the onset of substorms is to use low-latitude Pi2, which is sensitively related to the plasma instability in the magnetosphere, that triggers the substorm disturbances. This method is applied to examine the onset times of three substorm events which were already defined by various methods other than the low-latitude Pi2 method. Preceding the onset times, other evident substorm onsets are clearly determined with Pi2 onsets for all the three events by examining only the H-component of rapid-run magnetogram from a single low-latitude station in the dark hemisphere. Cooperative monitoring of Pi2 at three low-latitude stations on three well-separated meridians, therefore, is really effective in detecting most substorms }, keywords={ atmospheric techniques magnetic storms magnetosphere micropulsations magnetospheric substorm substorm onset plasma instability dark hemisphere low latitude Pi 2 pulsations substorm excitation geomagnetic micropulsations H-component }, mynotes={UNREAD}, } @ARTICLE{SakuraiJun76, author={Sakurai, T. and Saito, T.}, title={ Magnetic pulsation Pi2 and substorm onset }, journal={Planetary and Space Science}, volume={24}, number={6}, year={1976}, month={Jun}, pages={573-5}, abstract={ Coincidence between the onset of sudden brightening of the auroral arc in the auroral oval and the onset of Pi2 magnetic pulsation in low latitudes is examined based on the auroral data obtained at a chain of stations in Alaska and the Pi2 data obtained at the low-latitude station Onagawa. The result shows that the low-latitude Pi2 occurs almost simultaneously with the sudden brightening of the auroral arc, i.e. the onset of an auroral substorm (T=O). It is concluded that the onset of substorms can be identified quite well with the onset of the low-latitude Pi2 }, keywords={ aurora magnetic storms micropulsations substorm onset sudden brightening auroral arc auroral oval low latitudes Alaska Onagawa Pi 2 magnetic pulsations }, mynotes={UNREAD}, } @ARTICLE{AsaharaJun98, author={Asahara, Y. and Ohtani, E. and Sukuki, A.}, title={ Melting relations of hydrous and dry mantle compositions and the genesis of komatiites }, journal={Geophysical Research Letters}, volume={25}, number={12}, year={1998}, month={Jun}, pages={2201-4}, abstract={ The hydrous phase relations of primitive upper mantle model compositions in the CaO-MgO-Al/sub 2/O/sub 3/-SiO/sub 2/-H/sub 2/O system with 1, 2 and 5 wt.% H/sub 2/O have been investigated with a multi-anvil high pressure apparatus at 6.5 GPa and temperatures from 1550 degrees C to 2050 degrees C. Liquidus temperatures decrease by about 100 degrees C and the temperature interval to produce about 60% partial melting reduces to less than 50 degrees C in the 1-2 wt.% H/sub 2/O-bearing systems. At an H/sub 2/O content of about 5 wt.%, garnet is the first dissolved phase and the stability field of orthopyroxene expands. Aluminum undepleted komatiite magmas can be formed by melting at 200 km depth in a hydrous mantle at significantly lower temperatures than under dry conditions. Thus, komatiite magmas cannot constrain temperatures in the Archean mantle. In addition, cratonic peridotites may have formed as residues of partial melting under various H/sub 2/O contents }, keywords={ Earth mantle high-pressure effects high-temperature effects melting minerals terrestrial heat melting relations hydrous mantle compositions dry mantle compositions komatiite hydrous phase relations CaO-MgO-Al/sub 2/O/sub 3/-SiO/sub 2/-H/sub 2/O system multi-anvil high pressure observations liquidus temperatures partial melting H/sub 2/O-bearing systems garnet orthopyroxene Al undepleted komatiite magmas Archean mantle cratonic peridotites 1550 to 2050 degC 6.5 GPa CaO-MgO-Al/sub 2/O/sub 3/-SiO/sub 2/-H/sub 2/O H/sub 2/O }, mynotes={UNREAD}, } @ARTICLE{WatanabeApr98, author={Watanabe, M. and Iijima, L.T. and Nakagawa, M. and Potemra, T.A. and Zanetti, L.J. and Ohtani, S. and Newell, P.T.}, title={ Field-aligned current systems in the magnetospheric ground state }, journal={Journal of Geophysical Research}, volume={103}, number={A4}, year={1998}, month={Apr}, pages={6853-69}, abstract={ Using magnetic field or particle data obtained by the Magsat, DMSP-F6, and DMSP-F7 satellites, the authors have investigated characteristics of the magnetospheric plasma environment and field-aligned currents (FACs) during prolonged geomagnetic quiescence (K/sub p/=0) associated with extremely low values of the interplanetary magnetic field. The authors refer to this as the "ground state" of the magnetosphere. The large-scale FACs exhibit the traditional region 1/region 2 current pattern and the dayside region 0 (traditional cusp) current system. The median region 1 current intensity at 835-km altitude is 135 nT (with half of the values contained in the range 126-156 nT) in the 0800-1600 magnetic local time (MLT) region excluding the cusp. These are much smaller than the region 1 peak intensities of 740 nT for the ¹AL¹>or= 100 nT case and 350 nT for the ¹AL¹<100 nT case as statistically determined by Iijima and Potemra [1978]. In addition the region 1/region 2 FAC systems tend to degenerate into smaller-scale FACs at local times separated from the dayside toward morning and evening hours. The median region 1 intensity is 70 nT (with one-half the values between 52 and 96 nT) in the 2200-0200 MLT sector. In the prenoon and postnoon sectors, region 0 currents with intensities comparable to region 1 continue to be paired with region 1 currents. The region 0 and region 1 currents on the dayside extend in the azimuthal direction, are balanced in current intensity with a typical value of 140 nT in the 0915-1000 MLT sector, and are collocated with boundary layer particles. These observations have provided the first opportunity to study the basic flow patterns of field-aligned currents during the magnetospheric ground state }, keywords={ magnetosphere quiet conditions magnetosphere electric current field-aligned current system ground state magnetospheric ground state FAC geomagnetic quiescence quiet IMF }, mynotes={UNREAD}, } @ARTICLE{OhtaniOct97, author={Ohtani, S. and Elphinstone, R.D. and Troshichev, O.A. and Yamauchi, M. and Blomberg, L. and Zanetti, L.J. and Potemra, T.A.}, title={ Response of the dayside auroral and electrodynamic processes to variations in the interplanetary magnetic field }, journal={Journal of Geophysical Research}, volume={102}, number={A10}, year={1997}, month={Oct}, pages={22247-60}, abstract={ The response of the dayside auroral and electrodynamic processes to variations in the interplanetary magnetic field (IMF) is examined with multi-instrument data from the Viking Sweden and DMSP-F7 satellites as well as ground magnetometer data. The event selected, which occurred on October 5, 1986, was previously identified as a high-latitude dayside form by Murphree and Elphinstone (1988). This is one of 26 Viking-DMSP-F7 conjunction events found previously (Ohtani et al., 1995). In this event both Viking and DMSP-F7 traversed in the field of view of the Viking UV image. The authors examine solar wind conditions during the event. IMF B/sub Y/ was positive during most of the Viking auroral UV observation, whereas IMF B/sub Z/ made a transient southward excursion, followed by a sharp increase to +8 nT. The authors infer the ionospheric current-convection patterns and discuss the results }, keywords={ aurora electrodynamics interplanetary magnetic fields magnetosphere dayside auroral response electrodynamic processes interplanetary magnetic field variations Viking Sweden satellite DMSP-F7 satellite ground magnetometer data AD 1986 10 05 UV images solar wind conditions auroral UV observations }, mynotes={UNREAD}, } @ARTICLE{LewisMar97, author={Lewis, R.V. and Freeman, M.P. and Rodger, A.S. and Reeves, G.D. and Milling, D.K.}, title={ The electric field response to the growth phase and expansion phase onset of a small isolated substorm }, journal={Annales Geophysicae}, volume={15}, number={3}, year={1997}, month={Mar}, pages={289-99}, abstract={ We capitalise on the very large field of view of the Halley HF radar to provide a comprehensive description of the electric field response to the substorm growth phase and expansion phase onset of a relatively simple isolated substorm (¬AL¬<250 nT) which occurred on 13 June 1988. The substorm phases are identified by their standard ground magnetic and spacecraft energetic particle signatures, which provide a framework for the radar measurements. The substorm is preceded by a prolonged period (>12 h) of magnetic quiescence, such that prior to the start of the growth phase, the apparent latitudinal motion of the radar backscatter returns is consistent with the variation in latitude of the quiet-time auroral oval with magnetic local time. The growth phase is characterised by an increasing, superimposed equatorward motion of the equatorward edge of the radar backscatter as the auroral oval expands. Within this backscatter region, there is a poleward gradient in the Doppler spectral width, which we believe to correspond to latitudinal structure in auroral emissions and magnetospheric precipitation. During the growth phase the ionospheric convection is dominated by a relatively smooth large-scale flow pattern consistent with the expanding DP2 (convection) auroral electrojets. Immediately prior to substorm onset the ionospheric convection observed by the radar in the midnight sector has a predominantly equatorward flow component. At substorm onset a dramatic change occurs and a poleward flow component prevails. The timing and location are quite remarkable. The timing of the flow change is within one minute of the dispersionless injection observed at geostationary orbit and the Pi2 magnetic signature on the ground. The location shows that this sudden change in flow is due to the effect of the upward field aligned current of the substorm current wedge imposed directly within the Halley radar field of view }, keywords={ convection electric fields ionosphere magnetic storms magnetosphere plasma flow remote sensing by radar AD 1988 06 13 magnetosphere substorm electric field growth phase expansion phase onset Halley HF radar radar observation backscatter ionosphere convection plasma flow current wedge westward travelling surge isolated substorm plasma sheet magnetograms radar maps Doppler spectral width auroral oval }, mynotes={UNREAD}, } @ARTICLE{Bosinger87, author={Bosinger, T. and Yahnin, A.G.}, title={ Pi1B type magnetic pulsation as a high time resolution monitor of substorm development }, journal={Annales Geophysicae, Series A (Upper Atmosphere and Space Sciences)}, volume={5}, number={4}, year={1987}, month={}, pages={231-7}, abstract={ Out of a large collection of well-documented substorms (a result of the 'International Magnetospheric Study') several substorms are selected to demonstrate the possibility of monitoring substorm development by Pi1B type magnetic pulsations. Onset times and times of maximum Pi1B intensity are compared with characteristic times (e.g. onsets, sudden changes in the wave form) derived from Pi2 type magnetic pulsations observed at high and mid latitudes (Pi2 type magnetic pulsations are traditionally used as a substorm monitor). It is found that Pi1Bs and Pi2s are equally good substorm timers. The fine structure in the temporal development of the Pi1bs correlates well with Pi2 signatures and auroral activity }, keywords={ atmospheric techniques magnetic storms micropulsations AD 1977 micropulsation magnetosphere Pi1 Pi1B magnetic storm measurement technique Pi1B type magnetic pulsation substorm development monitoring }, mynotes={UNREAD}, } @ARTICLE{Luhr84, author={Luhr, H. and Klocker, N. and Thurey, S.}, title={ Ground-based observations of a very intense substorm-related pulsation event }, journal={Journal of Geophysics}, volume={55}, number={1}, year={1984}, month={}, pages={41-53}, abstract={ A very intense pulsation event with characteristics of the high-latitude Pi2 type occurred in northern Scandinavia on 2 November 1982 during the evening hours. The ionospheric phenomena associated with this event have been measured by the EISCAT magnetometer cross, by the Finnish riometer chain, and by the STARE facilities. The magnetic disturbances on the ground are explained in terms of intense and narrow electrojets extended in the south-east to north-west direction and drifting with a velocity of more than 2 km/s in the south-west direction. Just before the onset, the magnetometer chain was located on the poleward side of a well-developed Harang discontinuity. The pulsations started concurrently with a substorm onset and lasted for 40 min. Mapping STARE measurements into the magnetosphere the event is interpreted as kinetic Alfven waves generated near the boundary between differentially drifting plasma regions. From the combination of magnetometer and riometer measurements it is concluded that only odd numbered reflections of the prime event have been observed }, keywords={ atmospheric structure electrojets geomagnetic variations ionosphere magnetic storms magnetohydrodynamic waves magnetosphere micropulsations plasma geomagnetic micropulsations AD 1982 11 02 MHD waves high latitude Pi 2 pulsations magnetic storm intense narrow polar electrojets odd-numbered Alfven wave reflections plasma boundary magnetosphere convection electric field ionosphere-magnetosphere interaction very intense substorm-related pulsation event northern Scandinavia 2 November 1982 evening hours ionospheric phenomena EISCAT magnetometer cross Finnish riometer chain STARE facilities magnetic disturbances magnetometer chain poleward side Harang discontinuity substorm onset magnetosphere kinetic Alfven waves differentially drifting plasma regions }, mynotes={UNREAD}, } @ARTICLE{Iyemori80, title={ Time delay of the substorm onset from the IMF southward turning }, journal={Journal of Geomagnetism and Geoelectricity}, volume={32}, number={5}, year={1980}, month={}, pages={267-73}, abstract={ The time delay of the substorm onset defined by the onset of the earliest Pi2 magnetic pulsations from a southward turning of the north-south component of the interplanetary magnetic field (IMF-Bz) has been investigated for 21 characteristic IMF events. It was found that the time delay had little dependence on the intensity of the IMF southward component in the range of the intensity examined (i.e. from -1.5 to -9 nT), or rather it was constant (about 1 hr) except for a few cases. This result suggests that the time delay can be interpreted as a response time inherent in the magnetosphere }, keywords={ magnetic storms substorm onset IMF southward turning interplanetary magnetic field magnetosphere time delay magnetic storm solar wind }, mynotes={UNREAD}, } @ARTICLE{SaitoOct79, author={Saito, T. and Yumoto, K. and Aoyama, I. and Toyama, F. and Takahashi, T.}, title={ Typical mini-substorm and long-period Pi2 event observed by the Jikiken satellite on December 11, 1978 }, journal={Bulletin of the Institute of Space and Aeronautical Science, University ofTokyo B}, volume={15}, number={3B}, year={1979}, month={Oct}, pages={739-50}, abstract={ A typical long-period Pi2 event that was associated with a distinct mini-substorm took place at 1355 UT (2255 in 135 degrees east meridian time) on December 11, 1978, after a successive ten-day magnetically calm period. The event was observed simultaneously at both the Jikiken (Exos-B) satellite near an expanded plasmapause on the 21 h LT meridian and a ground-based station, Onagawa, on the approximately 23 h LT meridian. The plasmapause position before the substorm onset is estimated from the stimulated plasma wave experiment to be L>or approximately=6.3. A dynamic spectrum analysis of the data revealed that the observed main period of the Pi2 was 140 seconds at Jikiken, and both 140 and 220 seconds at Onagawa. The torsional oscillation model (namely, the plasma-sheet model) that an odd mode hydromagnetic torsional oscillation of the contracted dipole-like field-line that was excited by the distant plasma instability on a tail-like field-line is applied to explain the mechanism of the Pi2. The tail-like field-line whose apex was at >16.4 R/sub E/ is assumed to contract rapidly due to the instability to the dipole-like one with the apex at 9.2 R/sub E/. The period of 140 sec of the same Pi2 event observed at Jikiken is interpreted as a transient hydromagnetic surface wave excited secondarily on the with plasmapause. This mechanism is discussed in comparison with the Pg model that a hydromagnetic surface wave on the expanded plasmapause excited by a plasma instability on the plasmapause is observed as a giant pulsation in the auroral zone }, keywords={ artificial satellites geomagnetism ionosphere magnetic storms magnetohydrodynamics magnetosphere micropulsations Jikiken satellite expanded plasmapause 21 h LT meridian Onagawa plasmapause position substorm onset stimulated plasma wave experiment dynamic spectrum analysis odd mode hydromagnetic torsional oscillation distant plasma instability transient hydromagnetic surface wave giant pulsation auroral zone long period Pi 2 pulsation event minisubstorm MHD magnetic storm AD 1978 12 11 micropulsations pulsations main period contracted dipole like field line tail like magnetic field line magnetosphere plasma sheet plasmapause wave EXOS-B }, mynotes={UNREAD}, } @ARTICLE{SaitoNov76, author={Saito, T. and Yumoto, K. and Koyama, Y.}, title={ Magnetic pulsation Pi2 as a sensitive indicator of magnetospheric substorm }, journal={Planetary and Space Science}, volume={25}, number={11}, year={1976}, month={Nov}, pages={1025-9}, abstract={ The identification of substorm onset is quite important in studying the mechanism of excitation of substorm disturbances. At present, one of the most practical methods to identify accurately the onset of substorms is to use low-latitude Pi2, which is sensitively related to the plasma instability in the magnetosphere, that triggers the substorm disturbances. This method is applied to examine the onset times of three substorm events which were already defined by various methods other than the low-latitude Pi2 method. Preceding the onset times, other evident substorm onsets are clearly determined with Pi2 onsets for all the three events by examining only the H-component of rapid-run magnetogram from a single low-latitude station in the dark hemisphere. Cooperative monitoring of Pi2 at three low-latitude stations on three well-separated meridians, therefore, is really effective in detecting most substorms }, keywords={ atmospheric techniques magnetic storms magnetosphere micropulsations magnetospheric substorm substorm onset plasma instability dark hemisphere low latitude Pi 2 pulsations substorm excitation geomagnetic micropulsations H-component }, mynotes={UNREAD}, } @ARTICLE{SakuraiJun76, author={Sakurai, T. and Saito, T.}, title={ Magnetic pulsation Pi2 and substorm onset }, journal={Planetary and Space Science}, volume={24}, number={6}, year={1976}, month={Jun}, pages={573-5}, abstract={ Coincidence between the onset of sudden brightening of the auroral arc in the auroral oval and the onset of Pi2 magnetic pulsation in low latitudes is examined based on the auroral data obtained at a chain of stations in Alaska and the Pi2 data obtained at the low-latitude station Onagawa. The result shows that the low-latitude Pi2 occurs almost simultaneously with the sudden brightening of the auroral arc, i.e. the onset of an auroral substorm (T=O). It is concluded that the onset of substorms can be identified quite well with the onset of the low-latitude Pi2 }, keywords={ aurora magnetic storms micropulsations substorm onset sudden brightening auroral arc auroral oval low latitudes Alaska Onagawa Pi 2 magnetic pulsations }, mynotes={UNREAD}, } @ARTICLE{ChangNov75, author={Chang, R.P.H. and Lanzerotti, L.J.}, title={ On the generation of magnetohydrodynamic waves at the onset of a substorm }, journal={Geophysical Research Letters}, volume={2}, number={11}, year={1975}, month={Nov}, pages={489-91}, abstract={ Theoretical analysis of magnetoacoustic waves driven unstable by a neutral charged-particle beam suggests that such waves can be generated in the plasma sheet at the onset of a substorm. It is further suggested that the magnetohydrodynamic waves observed to occur at the onset of substorms (often called Pi2 pulsations) may be attributed to the coupling of resonant field lines on the nightside of the Earth. Experimental determinations of the distribution of resonant field lines for various frequency components of the waves, together with the theoretical concepts, can ultimately yield information on the inward velocity of hot plasma particles at substorm onsets }, keywords={ magnetic storms magnetohydrodynamic waves magnetosphere micropulsations plasma magnetoacoustic waves plasma sheet Pi2 pulsations hot plasma particles substorm onsets magnetohydrodynamic waves generation neutral charged particle beam Earth nightside locally resonant field lines inward velocity field lines distribution field line reconnection magnetotail }, mynotes={UNREAD}, } @ARTICLE{LinApr75, author={Lin, C.C. and Cahill, L.J., Jr.}, title={ Pi2 pulsations in the magnetosphere }, journal={Planetary and Space Science}, volume={23}, number={4}, year={1975}, month={Apr}, pages={693-711}, abstract={ Several substorms were observed at Explorer 45 in November and December, 1971, and January and February 1972, while the satellite was in the evening quadrant near L=5. These same substorms were identified in ground level magnetograms from auroral zone and low latitude stations. The satellite vector magnetic field records and rapid run ground magnetograms were examined for evidence of simultaneous occurrence of Pi2 magnetic pulsations. Pulsations which began abruptly were observed at the satellite during 7 of the 13 substorms studied and the pulsations occurred near the estimated time of substorm onset. These 7 pulsation events were also observed on the ground and 6 were identified in station comments as Pi2. All of the events were principally compressional waves, that is, pulsations in field magnitude. There were also transverse components elliptically polarized counter-clockwise looking along the field line. Periods observed ranged from 40 to 200 sec with 80 sec often the dominant period }, keywords={ magnetic storms magnetosphere micropulsations Pi2 pulsations magnetosphere substorms Explorer 45 vector magnetic field records ground magnetograms compressional waves }, mynotes={UNREAD}, } @ARTICLE{Pytte72, title={ Auroral-zone electron precipitation events observed before and at the onset of negative magnetic bays }, journal={Phys. Nor. (Norway), Physica Norvegica}, volume={6}, number={3-4}, year={1972}, month={}, pages={206}, abstract={ Balloon recordings of bremsstrahlung X-rays from precipitating electrons are presented, showing impulsive X-ray events just at the onset of bay activity as well as weaker and smoother electron precipitation before the bay, the latter apparently being connected with a growth phase of the same substorm. The prebay events are generally very smoothly varying events, but show modulation effects associated with the occurrence of irregular magnetic pulsations. The impulsive precipitation events start very abruptly together with Pi2 magnetic pulsations at bay onset, and show modulation effects, so that maxima in the X-ray flux tend to accompany maxima in the H-component at auroral-zone stations }, keywords={ aurora bremsstrahlung geomagnetic variations negative magnetic bays balloon recordings bremsstrahlung X-rays impulsive X-ray events bay activity prebay events modulation effects irregular magnetic pulsations auroral zone electron precipitation }, mynotes={UNREAD}, } @ARTICLE{LewisMar97, author={Lewis, R.V. and Freeman, M.P. and Rodger, A.S. and Reeves, G.D. and Milling, D.K.}, title={ The electric field response to the growth phase and expansion phase onset of a small isolated substorm }, journal={Annales Geophysicae}, volume={15}, number={3}, year={1997}, month={Mar}, pages={289-99}, abstract={ We capitalise on the very large field of view of the Halley HF radar to provide a comprehensive description of the electric field response to the substorm growth phase and expansion phase onset of a relatively simple isolated substorm (¬AL¬<250 nT) which occurred on 13 June 1988. The substorm phases are identified by their standard ground magnetic and spacecraft energetic particle signatures, which provide a framework for the radar measurements. The substorm is preceded by a prolonged period (>12 h) of magnetic quiescence, such that prior to the start of the growth phase, the apparent latitudinal motion of the radar backscatter returns is consistent with the variation in latitude of the quiet-time auroral oval with magnetic local time. The growth phase is characterised by an increasing, superimposed equatorward motion of the equatorward edge of the radar backscatter as the auroral oval expands. Within this backscatter region, there is a poleward gradient in the Doppler spectral width, which we believe to correspond to latitudinal structure in auroral emissions and magnetospheric precipitation. During the growth phase the ionospheric convection is dominated by a relatively smooth large-scale flow pattern consistent with the expanding DP2 (convection) auroral electrojets. Immediately prior to substorm onset the ionospheric convection observed by the radar in the midnight sector has a predominantly equatorward flow component. At substorm onset a dramatic change occurs and a poleward flow component prevails. The timing and location are quite remarkable. The timing of the flow change is within one minute of the dispersionless injection observed at geostationary orbit and the Pi2 magnetic signature on the ground. The location shows that this sudden change in flow is due to the effect of the upward field aligned current of the substorm current wedge imposed directly within the Halley radar field of view }, keywords={ convection electric fields ionosphere magnetic storms magnetosphere plasma flow remote sensing by radar AD 1988 06 13 magnetosphere substorm electric field growth phase expansion phase onset Halley HF radar radar observation backscatter ionosphere convection plasma flow current wedge westward travelling surge isolated substorm plasma sheet magnetograms radar maps Doppler spectral width auroral oval }, mynotes={UNREAD}, } @ARTICLE{AikioJan96, author={Aikio, A.T. and Kaila, K.U.}, title={ A substorm observed by EISCAT and other ground-based instruments-evidence for near-Earth substorm initiation }, journal={J. Atmos. Terr. Phys. (UK), Journal of Atmospheric and Terrestrial Physics}, volume={58}, number={1-4}, year={1996}, month={Jan}, pages={5-21}, abstract={ We present observations of the development of a substorm in the ionosphere made by the EISCAT radar, optical and magnetic instruments. A typical growth phase started 30 min before the substorm onset with equatorward drifting arcs. The arc which crossed the EISCAT beam drifted equatorward with approximately the same velocity as the ambient plasma and it approached the most equatorward discrete arc. The most equatorward discrete arc (the breakup arc) stopped its drift at L=5.3. Arcs about 1 degrees of latitude poleward of the breakup are continued their equatorward motion with no significant changes in intensity after the onset of the substorm, which was timed on the basis of the explosive intensification in the breakup arc. Similarly, no dramatic changes in electric fields or other plasma parameters measured by EISCAT were observed poleward of the breakup arc. The observations indicate that the instability that triggered the substorm onset was localized in the near-Earth magnetotail. A westward travelling surge (WTS) developed in the breakup arc and moved westward with a very high velocity, 13+or-3 km s/sup -1/. Extremely high conductances were measured by EISCAT from the poleward boundary of the poleward expanding bulge with a maximum value of Sigma /sub H/=214 S obtained with a time resolution of 0.2 s. The westward electrojet (WEJ) was observed to be latitudinally very inhomogenous and concentrated near conductivity enhancements, especially close to the head of the WTS. The localization of the WEJ close to discrete arcs and consequent motions with the arcs gave the characteristic spiky appearance of the magnetic X-component in the pre-midnight sector }, keywords={ atmospheric movements aurora electrojets ionospheric disturbances magnetic storms substorm EISCAT near-Earth substorm initiation ionosphere growth phase equatorward drifting arcs velocity breakup arc equatorward motion intensity explosive intensification electric fields plasma parameters instability near-Earth magnetotail westward travelling surge conductances westward electrojet conductivity enhancements magnetic X-component pre-midnight sector 13 km/s }, mynotes={UNREAD}, } @ARTICLE{TakahashiNov95, author={Takahashi, K. and Ohtani, S. and Anderson, B.J.}, title={ Statistical analysis of Pi 2 pulsations observed by the AMPTE CCE spacecraft in the inner magnetosphere }, journal={Journal of Geophysical Research}, volume={100}, number={A11}, year={1995}, month={Nov}, pages={21929-41}, abstract={ The spatial variation of the properties of magnetospheric Pi 2 pulsations is studied using magnetic field records acquired simultaneously by the Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer (AMPTE CCE) satellite at radial distances less than 6.6 Earth radii and at geomagnetic latitudes from -16 degrees to 16 degrees and at the Kakioka ground station located at magnetic shell of L=1.23. Pi 2 magnetic pulsations are identified from the Kakioka data acquired within 3 hours of midnight, but no restriction is imposed on the local time of CCE. An automated Pi 2 selection procedure resulted in 249 events from the Kakioka data. The authors have characterized magnetic field variations in the radial B/sub x/, azimuthal B/sub y/, compressional B/sub z/, components at CCE in terms of their spectral density, coherence, and phase relative to those of the Pi 2 pulsation in the horizontal H component of the Kakioka data and then examined how these parameters depend on the location of CCE. It is found that high-coherence events (coherence between CCE and Kakioka >0.6) are observed primarily when CCE is on the nightside and at L<4. For these events the magnetic field perturbations at CCE are dominated by the poloidal components B/sub x/ and B/sub z/, and these components exhibit a ground-to-satellite cross phase of either À0 or À180 degrees , depending on the location of the satellite. The spatial phase structure is consistent with the eigenmode structure of a compressional cavity-mode-type resonance excited between two reflecting boundaries. The authors find no evidence supporting the view that ground Pi 2 are midlatitude toroidal field line resonances excited in response to source waves on auroral zone field lines. Rather, the results imply that midlatitude (20 directly preceding the onset of the storm. An appropriate addition to ideas about the dynamics of B/sub z/ in the preliminary phase of a substorm is proposed }, keywords={ interplanetary magnetic fields magnetic storms magnetosphere peculiar magnetic substorm AD 1986 05 04 substorm preliminary phase substorm magnetic amplitude interplanetary magnetic field variations substorm onset B/sub z/-component southward turning B/sub z/-component dynamics magnetotail magnetic energy storage time May 4, 1986 intense explosive substorms magnetosphere 1 hr 800 to 900 nT }, mynotes={UNREAD}, } @ARTICLE{IgarashiJan85, author={Igarashi, K. and Ogawa, T. and Kuratani, Y. and Fujii, R. and Hirasawa, T.}, title={ Solar-terrestrial disturbances of June-September 1982. IV. Ionospheric disturbances. XIII. Aurora observation using the Syowa Station 50-MHz Doppler radar }, journal={Review of the Radio Research Laboratories}, volume={31}, number={}, year={1985}, month={Jan}, pages={193-9}, abstract={ A new 50-MHz Doppler radar with a minicomputer for real-time signal processing and radar control was installed at Syowa Station, Antarctica in February 1982. Strong geomagnetic disturbances occurred at about 00 h UT on the midnight of 14 July, 1982. Then a magnetic H-component decrease of about 4200 nT was observed at Syowa Station, and a decrease of about 630 nT was observed at Kakioka Magnetic Observatory. The 50-MHz backscatter echoes were received on 13-14 July 1982 during a substorm growth phase, so the rough estimates of the Doppler velocity in the third period were obtained. In this paper the Doppler spectra are discussed for SSC onset, substorm main phase and its recovery phase. The authors determined the large-scale electric field from combining the drift velocities along the two radar beams }, keywords={ atmospheric electricity atmospheric measuring apparatus Doppler effect ionosphere magnetic storms microcomputer applications plasma radar applications radar systems sudden storm commencement ionosphere disturbance atmosphere measuring apparatus AD 1982 06 to 09 auroral region plasma magnetic storm solar terrestrial Syowa Station 50-MHz Doppler radar signal processing Antarctica February 1982 14 July, 1982 magnetic H-component Kakioka Magnetic Observatory substorm growth phase Doppler velocity main phase recovery phase electric field drift velocities }, mynotes={UNREAD}, } @ARTICLE{OgawaJan85, title={ Solar-terrestrial disturbances of June-September 1982. III. Solar flares, flare particles and geomagnetic disturbances }, journal={Review of the Radio Research Laboratories}, volume={31}, number={}, year={1985}, month={Jan}, pages={19-39}, abstract={ Geomagnetic disturbances associated with solar-terrestrial events during the period June-September 1982 are investigated using data of both solar phenomena and the satellite GMS-2 which measured solar protons and alpha particles at geostationary orbit. According to an examination of world-wide magnetograms, it is tentatively suggested that the deep depression of the H-component during the July 13-14 storm was caused by an abnormal expansion of the substorm-associated current system in the auroral zone to the Far East. All the proton events due to flares in the eastern solar hemisphere were of slow-onset type. Only one example of fast-onset type was obtained for the west limb flare on July 22. The present analyses are compared with the big solar-terrestrial events which occurred in February 1958 and August 1972 }, keywords={ atmospheric electricity magnetic storms magnetosphere plasma solar flares solar-terrestrial relationships magnetosphere atmosphere plasma magnetic storm Sun AD 1982 06 to 09 flare particles geomagnetic disturbances solar-terrestrial events GMS-2 solar protons alpha particles H-component substorm-associated current system auroral zone slow-onset type fast-onset type }, mynotes={UNREAD}, } @ARTICLE{AggsonMay83, author={Aggson, T.L. and Heppner, J.P. and Maynard, N.C.}, title={ Observations of large magnetospheric electric fields during the onset phase of a substorm }, journal={Journal of Geophysical Research}, volume={88}, number={A5}, year={1983}, month={May}, pages={3981-90}, abstract={ A large impulsive westward electric field was observed in the mid-night, low latitude, dipole L=7.5 region of the magnetospheric tail at the onset of a large substorm. The measurements were made with the electric field probes carried by ISEE 1. The electric field impulse was coincident with a sharp 60 nT steplike change in the x component of the magnetic field at the satellite and the onset of a sharp 60 nT decrease in the H component of the field at a magnetic observatory near the subconjugate point. The 2-min envelope of the westward E/sub y/ field correlates with the time derivative delta B/sub x// delta t of the collapsing magnetic field attributed to the decrease in the cross-tail current. Associated with this inductive impulse, large electric field variations are also observed on time scales of tens of seconds to tens of milliseconds. The low-frequency (10 s) wave variations show a coherent phase relationship between the electric and magnetic field that changes from correlative to anti-correlative during the event. These large time-dependent electric fields seem to have the proper amplitude, duration, and timing relative to the auroral substorm sequence to explain the energetic proton enhancements frequently observed near midnight both at synchronous orbit and in the magnetotail at times of substorm onsets }, keywords={ magnetic storms magnetosphere magnetic storm magnetosphere night magnetotail magnetic tail AD 1978 04 19 large onset phase substorm impulsive electric field low latitude inductive }, mynotes={UNREAD}, } @ARTICLE{BakerOct81, author={Baker, D.N. and Hones, E.W. and Jr., Higbie and P.R. and Belian, R.D.}, title={ Global properties of the magnetosphere during a substorm growth phase: a case study }, journal={Journal of Geophysical Research}, volume={86}, number={A11}, year={1981}, month={Oct}, pages={8941-56}, abstract={ At approximately 0100 UT on December 29, 1976, a large injection of energetic (>30 keV) particles was observed by 1976-059 (35 degrees W longitude) at geostationary orbit. This injection was closely associated with the onset of a major substorm (also at 0100 UT) identified by sharp negative bays in the H components of magnetic records at Leirvogur (22 degrees W) and Narssarsuaq (45 degrees W) and by the occurrence of a positive H component bay at 0100 UT in the mid-latitude magnetogram record at M'Bour (17 degrees W). This substorm expansion onset was preceded by a pronounced 'stretching' of the magnetic field at synchronous orbit into a taillike configuration and by a development of highly cigar like (field-aligned) electron distributions at geostationary orbit that we have in the past identified with the substorm growth phase }, keywords={ magnetic storms magnetosphere magnetic storm AD 1976 12 29 magnetosphere substorm growth phase negative bays magnetic records Leirvogur Narssarsuaq M'Bour expansion onset magnetic field taillike configuration electron distributions geostationary orbit }, mynotes={UNREAD}, } @ARTICLE{SaitoNov76, author={Saito, T. and Yumoto, K. and Koyama, Y.}, title={ Magnetic pulsation Pi2 as a sensitive indicator of magnetospheric substorm }, journal={Planetary and Space Science}, volume={25}, number={11}, year={1976}, month={Nov}, pages={1025-9}, abstract={ The identification of substorm onset is quite important in studying the mechanism of excitation of substorm disturbances. At present, one of the most practical methods to identify accurately the onset of substorms is to use low-latitude Pi2, which is sensitively related to the plasma instability in the magnetosphere, that triggers the substorm disturbances. This method is applied to examine the onset times of three substorm events which were already defined by various methods other than the low-latitude Pi2 method. Preceding the onset times, other evident substorm onsets are clearly determined with Pi2 onsets for all the three events by examining only the H-component of rapid-run magnetogram from a single low-latitude station in the dark hemisphere. Cooperative monitoring of Pi2 at three low-latitude stations on three well-separated meridians, therefore, is really effective in detecting most substorms }, keywords={ atmospheric techniques magnetic storms magnetosphere micropulsations magnetospheric substorm substorm onset plasma instability dark hemisphere low latitude Pi 2 pulsations substorm excitation geomagnetic micropulsations H-component }, mynotes={UNREAD}, } @ARTICLE{SubbaraoNov73, author={Subbarao, S. and McPherron, R.L.}, title={ Statistical signature of isolated substorms at synchronous orbit }, journal={EOS Trans. Am. Geophys. Union (USA), EOS Transactions of the AmericanGeophysical Union}, volume={54}, number={11}, year={1973}, month={Nov}, pages={1176}, abstract={ The signature of a magnetospheric substorm at the ATS 1 satellite has traditionally been taken to be a depression and recovery in the H component of the magnetic field. These are thought to be the results of strengthening and inward motion of the tail current system at the beginning of the substorm, and the weakening and outward motion of the tail current at the end. Further, it has been shown that the recovery of the field at ATS 1 occurs after the ground onset in the pre-midnight period, and coincident with it at midnight and in post-midnight period. The substorm signature for the V and D components also is determined from this analysis. The seasonal dependence of the magnetic field components (V.D.H) is examined for the same period }, keywords={ magnetic storms magnetosphere statistical signature magnetospheric substorm tail current seasonal dependence magnetic field components }, mynotes={UNREAD}, } @ARTICLE{Pytte72, title={ Auroral-zone electron precipitation events observed before and at the onset of negative magnetic bays }, journal={Phys. Nor. (Norway), Physica Norvegica}, volume={6}, number={3-4}, year={1972}, month={}, pages={206}, abstract={ Balloon recordings of bremsstrahlung X-rays from precipitating electrons are presented, showing impulsive X-ray events just at the onset of bay activity as well as weaker and smoother electron precipitation before the bay, the latter apparently being connected with a growth phase of the same substorm. The prebay events are generally very smoothly varying events, but show modulation effects associated with the occurrence of irregular magnetic pulsations. The impulsive precipitation events start very abruptly together with Pi2 magnetic pulsations at bay onset, and show modulation effects, so that maxima in the X-ray flux tend to accompany maxima in the H-component at auroral-zone stations }, keywords={ aurora bremsstrahlung geomagnetic variations negative magnetic bays balloon recordings bremsstrahlung X-rays impulsive X-ray events bay activity prebay events modulation effects irregular magnetic pulsations auroral zone electron precipitation }, mynotes={UNREAD}, } @ARTICLE{PytteFeb72, author={Pytte, T. and Trefall, H.}, title={ Auroral-zone electron precipitation events observed before and at the onset of negative magnetic bays }, journal={Journal of Atmospheric and Terrestrial Physics}, volume={34}, number={2}, year={1972}, month={Feb}, pages={315-37}, abstract={ Balloon recordings of bremsstrahlung X-rays from precipitating electrons are presented, showing impulsive X-ray events just at the onset of bay activity as well as weaker and smoother electron precipitation before the bay, the latter apparently being connected with a growth phase of the same substorm. The pre-bay events are generally very smoothly varying events, but show modulation effects associated with the occurrence of irregular magnetic pulsations. The impulsive precipitation events start very abruptly together with P 2 magnetic pulsations at bay onset, and also show modulation effects, so that maxima in the X-ray flux tend to accompany maxima in the H-component at auroral-zone stations. These X-ray pulsations have a shorter period than the simultaneous mid-latitude Pi 2, which are taken to indicate that the impulsive precipitation events occur on field lines close to the inner edge of the neutral sheet }, keywords={ aurora electron precipitation events negative magnetic bays bremsstrahlung magnetic pulsations T auroral zone X-rays Pi 2 }, mynotes={UNREAD}, } @ARTICLE{MoldwinMay98, author={Moldwin, M.B. and Fernandez, M.I. and Rassoul, H.K. and Thomsen, M.F. and Bame, S.J. and McComas, D.J. and Fennell, J.F.}, title={ A reexamination of the local time asymmetry of lobe encounters at geosynchronous orbit: CRRES, ATS 5, and LANL observations }, journal={Journal of Geophysical Research}, volume={103}, number={A5}, year={1998}, month={May}, pages={9207-16}, abstract={ The local time of occurrence of a geosynchronous plasma flux dropout or lobe encounter is dependent on the longitude of the observing spacecraft. Satellites located on or west of the international Geomagnetic Reference Field (IGRF) model magnetic dip prime meridian (magnetic dip meridian) observe almost exclusively (77%) dawnside lobe encounters, while satellites located east of the magnetic dip meridian observe mostly duskside lobe encounters (67%). However, the transition from observing dawnside or duskside lobe encounters is not symmetric about the magnetic dip meridian. Three satellites (ATS 5, 1991-080, and 1990-095) located essentially at the magnetic dip meridian observed a majority (73%) of dawnside encounters. This study therefore concludes that there is a dawn-dusk asymmetry of the synchronous orbit altitude magnetic equatorial plane during active geomagnetic periods with the dawnside magnetosphere experiencing more radical distortions than the duskside. A case study of near-simultaneous lobe observations from CRRES and 1989-046 supports this conclusion. Note that it is found that the IGRF model dip prime meridian better organizes the local time occurrence frequency than does the magnetic dipole magnetic meridian, which has been shown to organize the seasonal dependence of geosynchronous lobe encounters in previous studies (i.e., Thomsen et al., 1994). Hence this study emphasizes the importance of considering the relative position of satellites with respect to both the magnetic dipole equator and the geomagnetic equator when utilizing geosynchronous plasma, magnetic field, and energetic particle data as diagnostics of the energy state of the magnetosphere }, keywords={ magnetosphere magnetosphere local time asymmetry lobe encounter geosynchronous orbit CRRES ATS 5 LANL local time of occurrence geosynchronous plasma flux dropout magnetic dip prime meridian magnetic dip meridian dawn-dusk asymmetry magnetic equatorial plane magnetic dipole magnetic meridian magnetic field configuration }, mynotes={UNREAD}, } @ARTICLE{Moldwin97, author={Moldwin, M.B. and Thomsen, M.F. and Reeves, G.D. and McComas, D.J.}, title={ The dynamic plasmasphere }, journal={Adv. Space Res. (UK), Advances in Space Research}, volume={20}, number={3}, year={1997}, month={}, pages={395-400}, abstract={ The outer plasmasphere is highly structured and very dynamic across a broad range of time and length scales. This is due to the interplay between refilling on the dayside and the erosion of the outer plasmasphere caused by variable magnetospheric convection. New results using data from geosynchronous orbit emphasize the importance of substorms to the structure and dynamics of the plasmasphere and suggest that the substorm growth phase plays an important role in populating the nightside inner magnetosphere with dense, cold plasma. Recent multi-satellite studies that examine plasmaspheric dynamics during the growth and expansive phases of substorms are reviewed }, keywords={ convection electrons ions magnetic fields magnetic storms magnetosphere plasmasphere dynamic magnetospheric convection substorms growth phase cold plasma nightside inner magnetosphere expansive phases ion density ion flux electron flux energetic ions energetic electrons magnetic field change }, mynotes={UNREAD}, } @ARTICLE{MoldwinApr97, title={ Outer plasmaspheric plasma properties: what we know from satellite data }, journal={Space Sci. Rev. (Netherlands), Space Science Reviews}, volume={80}, number={1-2}, year={1997}, month={Apr}, pages={181-98}, abstract={ Understanding of the composition, density, and temperature structure of the outer plasmasphere has undergone several major revisions since the discovery of the plasmasphere over 35 years ago. Each new era of understanding was brought about by the launching of satellites carrying suites of plasma diagnostic experiments each more sophisticated than its predecessor. Instead of each new generation of missions providing incremental advancement in knowledge of the plasmasphere's plasma properties, they most often than not, initiated a complete re-thinking of that understanding. There are still a number of observational "puzzles" and large gaps in how plasmaspheric structure and plasma properties change with geomagnetic storm and substorm activity. As new missions are developed to attempt to globally image the outer plasmasphere in order to put simultaneous multi-spacecraft observations into context, they will undoubtedly uncover new tantalizing observations that will cause the picture of the plasmasphere to be rethought. What has been learned from satellite data about the chemical composition, density, temperature and pitch-angle distribution properties and their variability is outlined in this review paper }, keywords={ magnetosphere plasma density plasma temperature outer plasmaspheric plasma properties satellite data density temperature structure outer plasmasphere plasma diagnostic experiments plasmaspheric structure geomagnetic storm activity substorm activity simultaneous multispacecraft observations chemical composition pitch-angle distribution }, mynotes={UNREAD}, } @ARTICLE{Moldwin96, author={Moldwin, M.B. and Thomsen, M.F. and McComas, D.J. and Reeves, G.D.}, title={ Dynamics and variability of the plasmasphere observed from synchronous orbit }, journal={AIP Conf. Proc. (USA), AIP Conference Proceedings}, volume={}, number={}, year={1996}, month={}, pages={45-8}, abstract={ The behavior of the cold ions in the outer plasmasphere is studied using data obtained with the magnetospheric plasma analyzers from multiple geosynchronous satellites. Dense (10-100 cm/sup -3/), cold (=1 eV) regions of plasma are often observed at geosynchronous orbit; in this study the authors refer to these as plasmaspheric intervals. The duration, local time of observation, density variability, and temperature behavior within these regions often depend in a systematic way on geomagnetic and substorm activity. With increasing geomagnetic activity (as indicated by Kp) the plasmaspheric regions are generally observed over shorter durations and at earlier local times. With increasing substorm activity (as indicated by geosynchronous energetic electron injections) the density becomes increasingly variable in these regions. Occasionally, up to order-of-magnitude density variations are observed over several minute timescales corresponding to regions with physical dimensions on the order of 1000 km or less. The appearance of these short-duration, cold-plasma intervals is strongly correlated with energetic ion and electron signatures both at the spacecraft making the plasmaspheric observations and at other spacecraft observing simultaneously in the midnight region. Such energetic particle signatures are indicative of the growth and expansive phase of geomagnetic substorms. The authors conclude that the appearance of these short-duration, plasmaspheric intervals is due to a reconfiguration of the duskside magnetosphere during geomagnetic substorms }, keywords={ magnetosphere magnetosphere plasmasphere cold ion dynamics variability geosynchronous orbit synchronous orbit cold ions outer plasmasphere dense plasma plasmaspheric interval magnetic substorm duskside magnetosphere }, mynotes={UNREAD}, } @ARTICLE{MoldwinMay95, author={Moldwin, M.B. and Thomsen, M.F. and Bame, S.J. and McComas, D.J. and Birn, J. and Reeves, G.D. and Nemzek, R. and Belian, R.D.}, title={ Flux dropouts of plasma and energetic particles at geosynchronous orbit during large geomagnetic storms: entry into the lobes }, journal={Journal of Geophysical Research}, volume={100}, number={A5}, year={1995}, month={May}, pages={8031-43}, abstract={ Geosynchronous orbit spacecraft occasionally observe the magnetospheric tail lobe during disturbed geomagnetic conditions. These lobe intervals are characterized by an absence of detectable ion flux above 1 eV and an absence of electron flux above several hundred eV. This study is an extension of Thomsen et al. (1994) and examines geosynchronous orbit plasma measurements for lobe encounters during a 4-year period involving three spacecraft, for a total of 85 spacecraft-months of observations. During the interval surveyed, 160 lobe encounters or close encounters were observed. These events are divided into the following two classes: events observed near midnight and those observed along the flanks. Both classes of events were strongly associated with very active geomagnetic conditions as indicated by Kp (mean value of 5), Dst (mean value of -104 nT), and the Auroral Boundary Index, particularly the flank events. Fifty percent of the lobe encounters occurred within +or-24 hours of a geosynchronous magnetopause crossing, which indicates that many of the lobe encounters occurred when there was severe compression and/or erosion of the magnetosphere. Most of the magnetopause-crossing-associated events were flank events. The flank-lobe events were also generally associated with a large interplanetary magnetic field magnitude, with the B/sub y/ or B/sub z/ component being dominant. Dropouts in the energetic electron and ion fluxes were observed concurrently with the thermal ion plasma dropouts, though they often extended over a longer time interval. For most of the events a geosynchronous injection of energetic electrons and/or protons was observed following the beginning of the thermal ion dropout, often at a different satellite than the one observing the lobe. For a limited subset of the lobe events (17 events) in which a GOES satellite was nearby, the magnetic field data indicate that the field is often highly stretched or radial near the time of the lobe events. The aut }, keywords={ magnetic storms magnetosphere radiation belts magnetosphere flux dropout energetic particle plasma geosynchronous orbit synchronous orbit large geomagnetic storm magnetic storm entry into lobe flank-lobe event reconfiguration solar wind disturbance tail lobe }, mynotes={UNREAD}, } @ARTICLE{MoldwinMay95, author={Moldwin, M.B. and Thomsen, M.F. and Bame, S.J. and McComas, D. and Reeves, G.D.}, title={ The fine-scale structure of the outer plasmasphere }, journal={Journal of Geophysical Research}, volume={100}, number={A5}, year={1995}, month={May}, pages={8021-9}, abstract={ The density and temperature structure of the low-energy ion population in the outer plasmasphere is examined by using data from Los Alamos National Laboratory's three-dimensional magnetospheric plasma analyzer at synchronous orbit. The authors define the "outer plasmasphere" as regions of dense, cold plasma observed at synchronous orbit, with no attempt to distinguish between the main plasmasphere or detached plasma regions existing beyond the plasmapause. The authors find that for moderate to high levels of geomagnetic activity the outer plasmasphere typically has a fine-scale density structure. The amount of variability in the density generally increases with increasing geomagnetic activity, as indicated by Kp, and the most variable intervals are associated with substorm activity. The dense (>10 ions cm/sup 3/), cold ( approximately=1 eV), plasmaspherelike plasma is adjacent to, and often interspersed with, low-density (1-10 ions cm/sup -3/), warm (2-10 eV), "troughlike" plasma regions. They find that occasionally these two temperature populations can coexist, but that most often they do not. The scale size of the fine-scale structure in the dense, cold plasma regions often is of the order of 1000 km or less. These observations suggest that fine-scale density structure in the dusk sector of the outer plasmasphere is imposed by penetrating substorm electric fields }, keywords={ magnetosphere magnetosphere fine-scale structure outer plasmasphere density temperature structure low-energy ion population satellite observations Los Alamos National Laboratory three-dimensional magnetospheric plasma analyzer dense cold plasma synchronous orbit geomagnetic activity magnetic activity dusk sector penetrating substorm electric fields }, mynotes={UNREAD}, } @ARTICLE{MoldwinJun94, author={Moldwin, M.B. and Thomsen, M.F. and Bame, S.J. and McComas, D.J. and Moore, K.R.}, title={ An examination of the structure and dynamics of the outer plasmasphere using multiple geosynchronous satellites }, journal={Journal of Geophysical Research}, volume={99}, number={A6}, year={1994}, month={Jun}, pages={11475-81}, abstract={ The structure and the dynamics of the plasmaspheric bulge are examined using in situ three-dimensional plasma observations from magnetospheric plasma analyzers onboard multiple geosynchronous satellites. The authors identify the plasmasphere by the presence of high fluxes of low-energy ( approximately=few eV) ions (corresponding to densities of approximately=10s up to approximately=100 cm/sup 3/). The results from one year (1991) of nearly continuous plasma measurements from two longitudinally and latitudinally separated spacecraft are presented. The study corroborates many of the features and statistical behavior of the plasmaspheric bulge evidenced in past ground-based and single spacecraft data sets, except the authors often find a more complex outer plasmasphere than earlier studies have suggested. By using multipoint, simultaneous observations to separate spatial from temporal changes, the study extends previous examinations of the plasmasphere at synchronous orbit. The authors find that the width and location of the plasmaspheric bulge can differ significantly for the two spacecraft (separated by 6-8 hours in time), particularly during quiet geomagnetic conditions. The very different plasmaspheric morphologies seen by the two spacecraft lead the authors to conclude that the outer plasmasphere is often highly structured even during steady geomagnetic conditions and that the simple teardrop model of the bulge rarely, if ever, adequately describes the duskside plasmasphere }, keywords={ magnetosphere plasma outer plasmasphere dynamics plasmaspheric bulge three-dimensional plasma observations magnetospheric plasma quiet geomagnetic conditions plasmaspheric morphologies teardrop model duskside plasmasphere AD 1991 }, mynotes={UNREAD}, } @ARTICLE{MoldwinJan94, author={Moldwin, M.B. and Hughes, W.J.}, title={ Observations of earthward and tailward propagating flux rope plasmoids: expanding the plasmoid model of geomagnetic substorms }, journal={Journal of Geophysical Research}, volume={99}, number={A1}, year={1994}, month={Jan}, pages={183-98}, abstract={ A survey of IMP 8 magnetometer data for plasmoid signatures during magnetospheric intervals from 1981 through 1983 found 16 plasmoids and 37 traveling compression regions as well as two earthward propagating flux ropes and 19 south-north bipolar lobe signatures. The properties of these relatively near-Earth plasmoids, traveling compression regions, and earthward propagating flux ropes and a qualitative model for their formation are presented. The plasmoids have estimated sizes, durations, magnetic field signatures, downtail velocities, and substorm associations very similar to those of the plasmoids identified in ISEE 3 deep-tail observations. The occurrence frequency of these near-Earth plasma sheet plasmoids is significantly smaller than that of plasmoids found in the mid- and deep tail with ISEE 3. The earthward propagating flux ropes are characterized by a south-north bipolar turning in the GSM B/sub z/ component, are localized near the noon-midnight meridional plane, and are strongly correlated with interplanetary magnetic field B/sub z/, north and small isolated high latitude geomagnetic substorms. These events are also apparently very rare and/or spatially localized. The authors propose that these structures are "proto-plasmoids", i.e., plasmoids for which near-Earth magnetic reconnection stopped before all the closed plasma sheet field lines were reconnected. The proto-plasmoids are then "trapped" inside closed magnetic field lines and propagate earthward owing to the effect of the distant X-line's earthward plasma }, keywords={ magnetic storms magnetosphere solar wind magnetosphere interaction tailward propagating flux rope plasmoid plasmoid model geomagnetic substorms magnetic storm magnetotail traveling compression regions earthward propagating south-north bipolar lobe model formation plasma sheet AD 1983 AD 1981 AD 1982 }, mynotes={UNREAD}, } @ARTICLE{MoldwinJan93, author={Moldwin, M.B. and Hughes, W.J.}, title={ Geomagnetic substorm association of plasmoids }, journal={Journal of Geophysical Research}, volume={98}, number={A1}, year={1993}, month={Jan}, pages={81-8}, abstract={ The relationship of geomagnetic substorms and plasmoids is examined by determining the correlation of the 366 plasmoids identified by Moldwin and Hughes (1992) with ground auroral zone magnetograms and geosynchronous particle data signatures of substorms onsets. Over 84% of the plasmoid events occurred between 5 and 60 min after a substorm onset. The authors also find near one-to-one correlation between large isolated substorm signatures in the near-Earth region and signatures consistent with a passing plasmoid in the distant tail. However, there does not appear to be an absolute correspondence of every substorm onset to a plasmoid signature in the deep tail especially for periods of prolonged disturbance that have multiple substorm onsets. A correlation of interplanetary magnetic field B/sub z/ south with plasmoid observations was also found }, keywords={ magnetic storms magnetosphere magnetosphere magnetic storm magnetotail IMF substorm association plasmoid onset distant tail B/sub z/ }, mynotes={UNREAD}, } @ARTICLE{MoldwinDec92, author={Moldwin, M.B. and Hughes, W.J.}, title={ On the formation and evolution of plasmoids: a survey of ISEE 3 Geotail data }, journal={Journal of Geophysical Research}, volume={97}, number={A12}, year={1992}, month={Dec}, pages={19259-82}, abstract={ ISEE 3 magnetometer and electron plasma measurements from the 1983 Geotail Mission were surveyed to determine the magnetic and plasma properties of plasmoids and their evolution with distance downtail. Events were selected on the basis of a bipolar magnetic signature in either the geocentric solar magnetospheric B/sub z/ and/or B/sub y/ component; most had B/sub z/ bipolar signatures. 366 events were found which is consistent with this signature while ISEE 3 was in the plasma sheet. ISEE 3 observed plasmoids all along its trajectory whenever it was in the plasma sheet. Plasmoids are characterized by high-speed plasma flow. Plasmoid length was determined using both the magnetometer and the electron plasma velocity data. Many plasmoids have a well-defined magnetic core field, characterized by a field strength maximum at the center of the pass through the structure. Plasmoids appear to be relatively stable structures once their formation process is complete }, keywords={ magnetosphere plasmoid magnetic tail magnetotail Earth magnetosphere AD 1983 formation evolution ISEE 3 Geotail plasma properties bipolar magnetic signature plasma sheet high-speed plasma flow length }, mynotes={UNREAD}, } @ARTICLE{MoldwinOct92, author={Moldwin, M.B. and Hughes, W.J.}, title={ Plasmoid observations in the distant plasma sheet boundary layer }, journal={Geophysical Research Letters}, volume={19}, number={19}, year={1992}, month={Oct}, pages={1911-14}, abstract={ Substorm-associated large amplitude bipolar magnetic events occurred when ISEE 3 was in the distant geotail's plasma sheet boundary layer (PSBL). The characteristics of these events, their substorm association, and their possible source mechanisms are examined. It is proposed that these PSBL events are signatures of a passing plasmoid in the plasma sheet, analogous to the traveling compression region model in the geomagnetic lobes }, keywords={ atmospheric movements magnetic storms magnetosphere plasma substorm-associated bipolar magnetic events magnetosphere substorm distant magnetotail magnetic field signatures AD 1983 05 13 AD 1983 03 19 AD 1983 07 22 distant plasma sheet boundary layer large amplitude bipolar magnetic events ISEE 3 passing plasmoid traveling compression region model geomagnetic lobes 5 to 20 nT 145 to 233 Earthradii }, mynotes={UNREAD}, } @ARTICLE{MoldwinAug91, author={Moldwin, M.B. and Hughes, W.J.}, title={ Plasmoids as magnetic flux ropes }, journal={Journal of Geophysical Research}, volume={96}, number={A8}, year={1991}, month={Aug}, pages={14051-64}, abstract={ Observational constraints on the magnetic topology and orientation of plasmoids is examined using a magnetic field model. The authors develop a magnetic flux rope model to examine whether principal axis analysis (PAA) of magnetometer signatures from a single satellite pass is sufficient to determine the magnetic topology of plasmoids and if plasmoid observations are best explained by the flux rope, closed loop, or large-amplitude wave picture. Model results are compared to ISEE 3 magnetometer data of plasmoid events in various coordinate frames including principal axis and geocentric solar magnetospheric }, keywords={ geomagnetism magnetic storms magnetosphere Earth magnetotail magnetosphere magnetic flux ropes magnetic topology orientation plasmoids magnetic field model principal axis analysis magnetometer signatures magnetic topology ISEE 3 magnetometer data }, mynotes={UNREAD}, } @ARTICLE{SpjeldvikFeb77, title={ Radiation belt electrons: structure of the loss cone }, journal={Journal of Geophysical Research}, volume={82}, number={4}, year={1977}, month={Feb}, pages={709-13}, abstract={ A critical analysis of existing theories for the structure of the atmospheric loss cone of energetic radiation belt electrons is presented. Emphasis is put on inadequacies and limitations of these theories. Some of the important error sources characteristic of experimental studies of the electron loss cone are also discussed and their effects assessed. Observations of energetic loss cone electrons obtained on board the satellite OV1-14 are presented and compared to theoretical predictions. The need for independent approaches is emphasized }, keywords={ atmospheric electron precipitation electrons radiation belts atmospheric loss cone energetic radiation belt electrons atmospheric electron precipitation OV1-14 satellite pitch angle distribution }, mynotes={UNREAD}, } @ARTICLE{SpjeldvikJun76, title={ The equilibrium radiation belt electron pitch angle distribution and its dependence on the radial diffusive source }, journal={Journal of Geophysical Research}, volume={81}, number={16}, year={1976}, month={Jun}, pages={2931-4}, abstract={ On the average, the population of radiation belt electrons reflects a balance between inward radial diffusion and turbulent losses to the atmosphere (e.g., Lyons and Thorne, 1973). The electron pitch angle distribution will therefore in general depend on the properties of both processes. To study its dependence on the source mechanism, the pitch angle diffusion equation is solved numerically for characteristic source angular distributions and quiet time turbulent wave-particle scattering rates. The equilibrium equatorial electron pitch angle distribution is shown to be only moderately dependent on the source structure and the shape of the loss cone distribution is found to be practically independent of source distributions for physically reasonable sources, the shape being controlled almost solely by the wave-particle scattering properties within the plasmasphere }, keywords={ atmospheric movements diffusion plasma plasma transport processes plasma turbulence radiation belts equilibrium radiation belt electron pitch angle distribution radial diffusive source inward radial diffusion turbulent losses pitch