Global dynamics of the plasmasphere and ring current during magnetic storms

Simultaneous global images of the plasmasphere and the ring current were ob tained with the Imager for Magnetopause-td-Aurora Global Exploration (IMAGE ) spacecraft during the geomagnetic storms of 24 May 2000 and 29 July 2000. The plasmasphere images confirm the theoretically predicted development of long plasma tails in the dusk hemisphere during magnetic storms. They also reveal several unexpected structures, including a sharp azimuthal gradient or shoulder, which forms on the night side and corotates with the Earth fo r many hours, and a narrow ion trough, which is located well inside the mai n plasmapause in the late evening sector. The ring current images show the peak of the ring current to be nearly centered on the plasmapause, which is consistent with ring current decay models that include coulomb scattering and wave-particle interactions as well as charge exchange.