Statistical Comparison of Electron Loss and Enhancement in the Outer Radiation Belt During Storms

Abstract

The near‐relativistic electron population in the outer Van Allen radiation belt is highly dynamic and strongly coupled to geomagnetic activity such as storms and substorms, which are driven by the interaction of the magnetosphere with the solar wind. The energy, content, and spatial extent of electrons in the outer radiation belt can vary on timescales of hours to days, dictated by the continuously evolving influence of acceleration and loss processes. While net changes in the electron population are directly observable, the relative influence of different processes is far from fully understood. Using a continuous 12 year data set from the Proton Electron Telescope on board the Solar Anomalous Magnetospheric Particle Explorer, we statistically compare the relative variations of trapped electrons to those in the bounce loss cone (BLC). Our results show that there is a proportional increase in flux entering the BLC outside the plasmapause during storm main phase and early recovery phase. Loss enhancement is sustained on the dawnside throughout the recovery phase while loss on the duskside is enhanced around minimum Sym‐H and quickly diminishes. Spatial variations are also examined in relation to geomagnetic activity, making comparisons to possible causal wave modes such as whistler‐mode chorus and plasmaspheric hiss.

Radial Transport in the Earth’s Radiation Belts: Linear, Quasi-linear, and Higher-order Processes

“…In open systems the impact of electromagnetic fluctuations will naturally lead to transport to the boundaries, and thus to irreversible losses. Terrestrial and planetary radiation belts are not closed systems and the inner and outer boundaries allow for particles' injection and losses (Millan & Thorne 2007;Aryan et al 2020;Walton et al 2022). However, the wave-particle interactions with ULF waves, in the absence of boundary effects, have to conserve phase-space density.…”

Examination of Radiation Belt Dynamics During Substorm Clusters: Magnetic Local Time Variation and Intensity of Precipitating Fluxes

“…The occurrence and magnitude of the differing drivers are typically dependent upon the distribution of cold plasma density with distance from the Earth (often described through the L‐shell parameter). This results in a clear delineation in the dynamics and losses of high‐energy electrons at the plasmapause (e.g., Walton et al., 2021, 2022). However, these competing driving processes are also strongly dependent upon magnetic local time (MLT).…”