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Pitch Angle Dependence of Energetic Electron Precipitation: Energy Deposition, Backscatter, and the Bounce Loss Cone
Author(s) -
Marshall R. A.,
Bortnik J.
Publication year - 2018
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024873
Subject(s) - pitch angle , electron precipitation , atmosphere (unit) , computational physics , physics , electron , van allen radiation belt , deposition (geology) , radiation , backscatter (email) , monte carlo method , particle (ecology) , optics , geophysics , plasma , meteorology , nuclear physics , magnetosphere , geology , paleontology , telecommunications , sediment , computer science , wireless , statistics , mathematics , oceanography
Quantifying radiation belt precipitation and its consequent atmospheric effects requires an accurate assessment of the pitch angle distribution of precipitating electrons, as well as knowledge of the dependence of the atmospheric deposition on that distribution. Here Monte Carlo simulations are used to investigate the effects of the incident electron energy and pitch angle on precipitation for bounce period time scales, and the implications for both the loss from the radiation belts and the deposition in the upper atmosphere. Simulations are conducted at discrete energies and pitch angles to assess the dependence on these parameters of the atmospheric energy deposition profiles and to estimate the backscattered particle distributions. We observe that the atmospheric response is both energy and pitch angle dependent. These effects together result in an energy‐dependent bounce loss cone angle, which can vary by 2–3° with particle energy when considered at low‐Earth orbit. This modeling also predicts that a significant fraction of the input electron distribution will be backscattered and should be observable by low‐Earth‐orbiting satellites as field‐aligned beams emerging from the atmosphere at energies lower than the input distribution and having pitch angles distributed just inside the loss cone.