The Effect of Plasmaspheric Plumes on the Loss of Ring Current Electrons

Low-energy ring current electrons of up to 50 keV represent a major threat to spacecrafts within the inner magnetosphere since they are one of the main causes of spacecraft surface charging. Furthermore, they can provide a seed population for relativistic radiation belt electrons during geomagnetic storms. In this work, we report the first results of coupling the Versatile Electron Radiation Belt (VERB) code with a fully MLT resolved physics-based plasmasphere model to investigate the loss mechanisms of low energy electrons. Our four dimensional ring current model used in this study includes radial diffusion, convection, and loss due to whistler-mode chorus and hiss waves. The physics-based model of the plasmasphere includes convection of cold plasma and refilling from the ionosphere.
We simulate two storm events from the Van Allen Probes' era and compare results of cold plasma density and electron flux against measurements from the twin Van Allen Probe satellites. Our plasmasphere model is not only capable of predicting the plasmapause location but also the formation of plasmaspheric plumes, where plume whistler mode waves propagate. Including the plume region, which usually has very restricted spatial coverage, allows us to examine the effect of plume whistler mode waves on the loss of ring current electrons during these two events. These plasma boundaries show significant dynamics during the main and recovery phase of storms and are crucial to correctly predict electron loss.
By using the extracted plasma boundaries to determine the spatial extent of different waves species, we find better agreement of electron flux results with measurements, especially during the main phase of storms. We also report on the first ring current simulation results including the loss introduced by spatially localised whistler-wave scattering in plasmaspheric plumes.