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Time Scales for Electron Quasi‐linear Diffusion by Lower‐Band Chorus Waves: The Effects of ω pe / Ω ce Dependence on Geomagnetic Activity
Author(s) -
Agapitov O.,
Mourenas D.,
Artemyev A.,
Hospodarsky G.,
Bonnell J.W.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl083446
Subject(s) - van allen radiation belt , van allen probes , physics , electron , chorus , plasmasphere , diffusion , computational physics , atomic physics , amplitude , pitch angle , acceleration , local time , magnetosphere , geophysics , plasma , optics , nuclear physics , classical mechanics , art , statistics , literature , mathematics , thermodynamics
Electron scattering by chorus waves is an important mechanism that can lead to fast electron acceleration and loss in the outer radiation belt. Making use of Van Allen Probes measurements, we present the first statistical survey of megaelectron volt electron pitch angle and energy quasi‐linear diffusion rates by chorus waves as a function of L ‐shell, local time, and AE index, taking into account the local electron plasma frequency to gyrofrequency ratio ω pe / Ω ce , chorus wave frequency, and resonance wave amplitude. We demonstrate that during disturbed periods, ω pe / Ω ce strongly decreases in the night sector, leading to a faster electron loss but also a much faster electron energization in two distinct regions just above the plasmapause and at L ~ 3.5–5.5. Spatiotemporal variations of ω pe / Ω ce with AE shape the evolution of electron energization in the outer belt, sometimes leading to very short time scales for quasi‐linear megaelectron volt electron acceleration in agreement with Van Allen Probes observations.