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Energetic Proton Spectra Measured by the Van Allen Probes
Author(s) -
Summers Danny,
Shi Run,
Engebretson Mark J.,
Oksavik Kjellmar,
Manweiler Jerry W.,
Mitchell Donald G.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024484
Subject(s) - proton , spectral line , cyclotron , physics , van allen probes , ring current , limiting , scattering , ion , atomic physics , computational physics , nuclear physics , van allen radiation belt , magnetosphere , electron , astronomy , optics , plasma , mechanical engineering , quantum mechanics , engineering
We test the hypothesis that pitch angle scattering by electromagnetic ion cyclotron (EMIC) waves can limit ring current proton fluxes. For two chosen magnetic storms, during 17–20 March 2013 and 17–20 March 2015, we measure proton energy spectra in the region 3 ≤ L ≤ 6 using the RBSPICE‐B instrument on the Van Allen Probes. The most intense proton spectra are observed to occur during the recovery periods of the respective storms. Using proton precipitation data from the POES (NOAA and MetOp) spacecraft, we deduce that EMIC wave action was prevalent at the times and L ‐shell locations of the most intense proton spectra. We calculate limiting ring current proton energy spectra from recently developed theory. Comparisons between the observed proton energy spectra and the theoretical limiting spectra show reasonable agreement. We conclude that the measurements of the most intense proton spectra are consistent with self‐limiting by EMIC wave scattering.