Evidence of Residual Plasmaspheric Plumes

Plasmaspheric erosion produces plumes of plasma that extend sunward from the main torus. When geomagnetic activity decreases, a given plume loses its sunward orientation, rotating eastward and wrapping itself around the plasmasphere torus. The residual plume is a major feature of the recovery phase plasmasphere, and is suspected to be an important influence upon the loss rates of energetic particles. In this study, comparison between in situ observations of the Los Alamos National Laboratory (LANL) Magnetospheric Plasma Analyzers (MPA) and output of a plasmapause test particle (PTP) simulation for the moderately disturbed interval 18--20 January 2000 reveals evidence of plasmaspheric plumes that wrapped completely around the main torus and lasted for at least 40 hours and possibly as long as 60 hours. The presence of long-lived multiple wrapped residual plumes suggests that the global plasmaspheric density distribution preserves some memory of prior epochs of erosion and recovery.