Quantifying the Contribution of Microbursts to Global Electron Loss in the Radiation Belts

Abstract

We use the Solar, Anomalous, and Magnetospheric Particle Explorer to explore the relationship between microbursts and global flux decay of electrons from the outer Van Allen belt during the recovery phase of geomagnetic storms. We investigate the correlation between microbursts and global electron loss in each of the quasi-trapped (drift loss cone), stably trapped, and untrapped electron (bounce loss cone) populations. For the quasi-trapped electrons, we separately classify the storms as driven by coronal mass ejections or corotating interaction regions and explore their connection to microburst loss. We find that the decay lifetime of electron fluxes, that is, e-folding times of macroscopic fluxes in the recovery phase is correlated with strong microburst activity. That is, when the microburst activity is high, global flux decay times are short, and vice versa, suggesting a cross-scale coupling between microloss and macroloss phenomena. Furthermore, we find that the microburst to global loss coupling is predominant in the quasi-trapped population of radiation belt electrons while having negligible influence on the untrapped and stably trapped populations. We find that microburst activity during storms driven by coronal mass ejections is coupled more strongly with global flux decay as compared with corotating interaction regions. In addition, we find that distance from the plasmapause is likely a better indicator of microburst location than L-shell, with most microbursts occurring ~0.5–2.0 L from the model plasmapause location.