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Upper Limit of Electron Fluxes Observed in the Radiation Belts
Author(s) -
Zhang Kun,
Li Xinlin,
Zhao Hong,
Xiang Zheng,
Khoo Leng Ying,
Zhang Wenxun,
Hogan Benjamin,
Temerin Michael A.
Publication year - 2021
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2020ja028511
Subject(s) - van allen radiation belt , physics , flux (metallurgy) , electron , van allen probes , magnetosphere , space weather , earth's magnetic field , geomagnetic storm , energy flux , atomic physics , computational physics , nuclear physics , geophysics , magnetic field , chemistry , plasma , quantum mechanics , organic chemistry
Abstract Radiation belt electrons have a complicated relationship with geomagnetic activity. We select electron measurements from 7 years of DEMETER and 6 years of Van Allen Probes data during geomagnetic storms to conduct statistical analysis focusing on the correlation between electron flux and Dst index. We report, for the first time, an upper limit of electron fluxes observed by both satellites throughout the inner and outer belts across a wide energy range from ∼100s keV to multi‐MeV. The upper flux limit is determined at different L 's and energies, for example, 1.9 × 10 7 /cm 2 ‐s‐sr‐MeV at 470 keV at L = 1.5 and 3.6 × 10 5 /cm 2 ‐s‐sr‐MeV at 3.4 MeV at L = 4 (Van Allen Probes). We present the energy spectra of the electron flux upper limit at different L shells and find the measured upper flux limit to be at least three times higher than the predicted flux from the AE8/AE9 models, although the spectral shape is remarkably similar. We show that the average flux with an applied time lag is better correlated with the Dst index and that the time lag optimizing the correlation coefficient is larger at lower L and at higher energies. These findings present the underlying challenges to model the dynamic variation of relativistic electrons in the inner magnetosphere and are important information for space weather considerations.