Comparison of energetic electron intensities outside and inside the radiation belts

Abstract

The intensities of energetic electrons (~25-800 keV) outside and inside Earth's radiation belts are reported using measurements from Time History of Events and Macroscale Interactions during Substorms and Van Allen Probes during nongeomagnetic storm periods. Three intervals of current disruption/dipolarization events in August 2013 were selected for comparison. The following results are obtained. (1) Phase space densities (PSDs) for the equatorially mirroring electron population at three values of the first adiabatic invariant (20, 70, and 200 MeV/G) at the outer radiation belt boundary are found to be 1 to 3 orders of magnitude higher than values measured just inside the radiation belt. (2) There is indication that substorm activity leads to PSD increases inside L = 5.5 in less than 1 h. (3) Evidence for progressive inward transport of enhanced PSDs is found. (4) Reductions and enhancements in the PSDs over L shells from 3.5 to 6 are found to occur rapidly in~2-3 h. These results suggest that (1) continual replenishments are required to maintain high levels of PSD for electrons at these energies and (2) inward radial transport of these electrons occurs in a fast timescale of a few hours.

The Radial Propagation Characteristics of the Injection Front: A Statistical Study Based On BD‐IES and Van Allen Probes Observations

“…Therefore, magnetic moments ( μ ) are conserved and of course the μ uc of injected electrons at different L shells are equal. Recently, based on multisatellite observations from THEMIS, Lui () and Lui et al (, ) demonstrated that the source strength of energetic electrons associated with dipolarization at the outer radiation belt boundary during both quiet and storm periods is adequate to account for the electron intensity in the outer radiation belt, if electrons could be transported inward without significant loss. Therefore, it is possible that injected electrons observed in the inner magnetosphere come from higher L shells.…”

“…At even larger distances, however, it becomes too small to be detected. The relationship between radial location of the injections and geomagnetic activity was also studied (e.g., Gabrielse et al, 2014;Lopez et al, 1990;Mauk & Mcilwain, 1974). Statistically, injections can reach lower L shells with increased geomagnetic activities.…”