Modeling the Electron Flux Enhancement and Butterfly Pitch Angle Distributions on L Shells <2.5

TitleModeling the Electron Flux Enhancement and Butterfly Pitch Angle Distributions on L Shells <2.5
Publication TypeJournal Article
Year of Publication2019
AuthorsHua, M, Li, W, Ma, Q, Ni, B, Nishimura, Y, Shen, X‐C, Li, H
JournalGeophysical Research Letters
Pagination10967 - 10976
Date Published09/2019
Keywords3‐D radial belt modeling; Butterfly pitch angle distribution; Electron flux enhancement; inner belt and slot region; Inward radial diffusion; local wave‐particle interactions; Van Allen Probes
AbstractWe analyze an energetic electron flux enhancement event in the inner radiation belt observed by Van Allen Probes during an intense geomagnetic storm. The energetic electron flux at L~1.5 increased by a factor of 3 with pronounced butterfly pitch angle distributions (PADs). Using a three‐dimensional radiation belt model, we simulate the electron evolution under the impact of radial diffusion, local wave‐particle interactions including hiss, very low frequency transmitters, and magnetosonic waves, as well as Coulomb scattering. Consistency between observation and simulation suggests that inward radial diffusion plays a dominant role in accelerating electrons up to 900 keV and transporting the butterfly PADs from higher L shells to form the butterfly PADs at L~1.5. However, local wave‐particle interactions also contribute to drive butterfly PADs at L ≳ 1.9. Our study provides a feasible mechanism to explain the electron flux enhancement in the inner belt and the persistent presence of the butterfly PADs at L~1.5.
Short TitleGeophys. Res. Lett.

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