Substorm injections produce sufficient electron energization to account for MeV flux enhancements following some storms

Abstract

[1] One of the main questions concerning radiation belt research is the origin of very high energy (>1 MeV) electrons following many space storms. Under the hypothesis that the plasma sheet electron population is the source of these electrons, which are convected to the outer radiation belt region during substorms, we estimate the flux of particles generated at geosynchronous orbit. We use the test particle method of following guiding center electrons as they drift in the electromagnetic fields during substorm dipolarization. The dipolarization pulse model electromagnetic fields are taken from the Li et al. (1998) substorm particle injection model. We find that a substorm dipolarization can produce enough electrons within geosynchronous orbit to account for the electrons seen following storms. To do this, we compute transport ratios of plasma sheet electrons, that is, the relative ratio of plasma sheet electrons that are transported and trapped in the inner magnetosphere during substorms, as well as the change in energy of the electrons. Since high fluxes of MeV electrons are only seen following storms and not isolated substorms, it is likely that these electrons may serve as a source population for other energization mechanisms which accelerate the electrons to MeV energies. Furthermore, we do parametric studies of the dipolarization model to understand physically what conditions enable the generation of this source population. Copyright 2005 by the American Geophysical Union.