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Radioscience Seminars

EE 350 Radioscience Seminar
Professor Umran S. Inan
Winter 2004-2005

Date: Wednesday, February 23, 2005
Time: 4:15 PM – Refreshments at 4:00
Location: Sloan Mathematics Center (Building 380), Room 380Y

Generation of ULF Waves in Radiation Belts by Chemical Release
Dr. Gurudas Ganguli
Plasma Physics Division, Naval Research Laboratory

In 1970 Brice [1] noted that it is possible to artificially enhance the energetic particle precipitation rate in the radiation belts by cold plasma injection. Since then creation of plasma clouds in the radiation belts via chemical release has been studied both theoretically and experimentally but these studies were mainly restricted to high altitudes (L ~ 4 - 5). We have examined the possibility of generating electromagnetic ion-cyclotron (ULF) waves by chemical release at inner radiation belt altitudes (L < 2). We show that ionization of the released chemicals can result in the formation of an ion ring distribution perpendicular to the ambient magnetic field in a manner that is similar to the comet-solar wind interaction. Such an ion distribution is highly unstable to both electrostatic and electromagnetic instabilities. We have compared the possible electrostatic and electromagnetic instabilities that may be generated by such ion distributions, assessed their properties, and quantified the parametric domains and conditions where particular modes dominate. The electrostatic ion-cyclotron modes of the ion ring distribution can be stabilized by Landau damping of the ambient plasma. This allows the electromagnetic ion-cyclotron modes to dominate since they are not subjected to Landau damping. The quasi-stationary turbulent spectra can be sustained by fresh supply of ring ions through ionization. The threshold density and other parameters that result in predominance of electromagnetic modes and their role in particle loss mechanisms in the radiation belts will be discussed. * This work is supported by ONR [1] Brice, N., Artificial enhancement of energetic particle precipitation through cold plasma injection, J. Geophys. Res., 75, 4890, 1970.