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POES/MEPED Angular Response Functions and the Precipitating Radiation Belt Electron Flux
Author(s) -
Selesnick R. S.,
Tu Weichao,
Yando K.,
Millan R. M.,
Redmon R. J.
Publication year - 2020
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2020ja028240
Subject(s) - pitch angle , electron , van allen radiation belt , physics , diffusion , azimuth , flux (metallurgy) , computational physics , proton , telescope , radiation , energy flux , energy (signal processing) , atomic physics , optics , materials science , geophysics , plasma , magnetosphere , nuclear physics , astronomy , quantum mechanics , metallurgy , thermodynamics
Angular response functions are derived for four electron channels and six proton channels of the SEM‐2 MEPED particle telescopes on the POES and MetOp satellites from Geant4 simulations previously used to derive the energy response. They are combined with model electron distributions in energy and pitch angle to show that the vertical 0° telescope, intended to measure precipitating electrons, instead usually measures trapped or quasi‐trapped electrons, except during times of enhanced pitch angle diffusion. A simplified dynamical model of the radiation belt electron distribution near the loss cone, as a function of longitude, energy, and pitch angle, that accounts for pitch angle diffusion, azimuthal drift, and atmospheric backscatter is fit to sample MEPED electron data at L = 4 during times of differing diffusion rates. It is then used to compute precipitating electron flux, as function of energy and longitude, that is lower than would be estimated by assuming that the 0° telescope always measures precipitating electrons.