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

Author
Keywords
Abstract
We 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.
Year of Publication
2019
Journal
Geophysical Research Letters
Volume
46
Number of Pages
10967-10976
Date Published
09/2019
ISSN Number
0094-8276
URL
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL084822
DOI
10.1029/2019GL084822