Abstract
IMAGE is the first satellite mission dedicated to imaging the Earth's magnetosphere, the region of space controlled by the Earth's magnetic field and containing extremely tenuous plasmas of both solar and terrestrial origin. These populations of ions and electrons have traditionally been studied by means of localized measurements with charged particle detectors, magnetometers, and electric field instruments. Instead of such in situ measurements, IMAGE employs a variety of imaging techniques to produce the first comprehensive global images of the plasma populations in the inner magnetosphere. With these images, we are able to observe, in a way never before possible, the large-scale dynamics of the magnetosphere and the interactions among its constituent plasma populations.
Within the magnetosphere, the plasmasphere is a region of cold, dense plasma populated by upflow of ionospheric plasma along geomagnetic field lines. Driven directly by the solar wind flow past the magnetosphere, global magnetospheric convection erodes the outer layers of the plasmasphere. Erosion causes the plasmasphere outer boundary, the plasmapause, to move inward on the nightside and outward on the dayside to form plumes of dense plasma extending sunward into the outer magnetosphere. Coupling between inner magnetosphere and the ionosphere can significantly modify the externally driven convection field, either enhancing sunward flows near dusk or shielding them on the night side. The plasmaspheric configuration plays a crucial role in the inner magnetosphere; wave-particle interactions inside the plasmasphere can cause scattering and loss of warmer space plasmas such as the ring current and radiation belts.