Improved Modeling of Inner Magnetosphere Electron Losses By Inclusion of a Plasmasphere

Abstract:

The buildup and dissipation of plasma in the inner magnetosphere is a complex process that is governed by many factors. One important factor is the rate of pitch-angle diffusion of trapped electrons into the precipitation loss cone. This loss rate is not only important for understanding the dynamics of energetic electrons. Rather, because of the coupled dynamics of the inner magnetosphere system, the loss of energetic electrons feeds back on the electric fields (via auroral ionospheric conductance enhancements), which in turn modify the drift paths of all ions and electrons. But describing the loss of electrons is a challenging problem. One important population of inner magnetosphere plasma that is highly relevant for calculating electron losses, and one which our model—the Rice Convection Model-Equilibrium (RCM-E)—has neglected, is the cold plasma population of the plasmasphere. Because the plasmasphere contains the bulk of the mass of plasma in the inner magnetosphere, it plays a dominant role in determining the plasma wave environment that drives diffusion and losses of electrons. At the very least, the location of the outer boundary of the plasmasphere (the plasmapause), at which the plasmaspheric density drops sharply, needs to be modeled in order to determine the regions where various wave modes operate (whistler-mode chorus, plasmaspheric hiss, and electromagnetic ion-cyclotron waves). In this study we present results of the RCM-E that include a cold plasma population whose source is ionospheric outflow, and whose shape is determined by ExB drift in the self-consistent fields of the RCM-E. We also present comparisons with Van Allen Probes data showing how our modeled plasmapause location compares with observational data during the 1-June-2013 magnetic storm, and how it affects the electron losses and, in turn, the ion and electron transport.