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Diffusive scattering of electrons by electron holes around injection fronts
Author(s) -
Vasko I. Y.,
Agapitov O. V.,
Mozer F. S.,
Artemyev A. V.,
Krasnoselskikh V. V.,
Bonnell J. W.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023337
Subject(s) - electron , scattering , physics , electron scattering , computational physics , pitch angle , atomic physics , diffusion , optics , quantum mechanics , geophysics
Van Allen Probes have detected nonlinear electrostatic spikes around injection fronts in the outer radiation belt. These spikes include electron holes (EH), double layers, and more complicated solitary waves. We show that EHs can efficiently scatter electrons due to their substantial transverse electric fields. Although the electron scattering driven by EHs is diffusive, it cannot be evaluated via the standard quasi‐linear theory. We derive analytical formulas describing local electron scattering by a single EH and verify them via test particle simulations. We show that the most efficiently scattered are gyroresonant electrons (crossing EH on a time scale comparable to the local electron gyroperiod). We compute bounce‐averaged diffusion coefficients and demonstrate their dependence on the EH spatial distribution (latitudinal extent and spatial filling factor) and individual EH parameters (amplitude of electrostatic potential, velocity, and spatial scales). We show that EHs can drive pitch angle scattering of ≲ 5 keV electrons at rates 10 −2 −10 −4 s −1 and, hence, can contribute to electron losses and conjugated diffuse aurora brightenings. The momentum and pitch angle scattering rates can be comparable, so that EHs can also provide efficient electron heating. The scattering rates driven by EHs at L shells L ∼ 5–8 are comparable to those due to chorus waves and may exceed those due to electron cyclotron harmonics.