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The effect of different solar wind parameters upon significant relativistic electron flux dropouts in the magnetosphere
Author(s) -
Gao Xinliang,
Li Wen,
Bortnik Jacob,
Thorne Richard M.,
Lu Quanming,
Ma Qianli,
Tao Xin,
Wang Shui
Publication year - 2015
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja021182
Subject(s) - magnetopause , physics , magnetosphere , solar wind , geophysics , electron precipitation , van allen radiation belt , interplanetary magnetic field , polar wind , electron , astrophysics , atmospheric sciences , computational physics , plasma , quantum mechanics
Superposed epoch analyses were performed on 193 significant relativistic electron flux dropout events, in order to study the roles of different solar wind parameters in driving the depletion of relativistic electrons, using ~16 years of data from the POES and GOES missions, and the OMNIWEB solar wind database. We find that the solar wind dynamic pressure and interplanetary magnetic field (IMF) B z play key roles in causing the relativistic electron flux dropouts, but also that either large solar wind dynamic pressure or strong southward IMF B z by itself is capable of producing the significant depletion of relativistic electrons. The relativistic electron flux dropouts occur not only when the magnetopause is compressed closer to the Earth but also when the magnetopause is located very far (> ~10 R E ). Importantly, our results show that in addition to the large solar wind dynamic pressure, which pushes the magnetopause inward strongly and causes the electrons to escape from the magnetosphere, relativistic electrons can also be scattered into the loss cone and precipitate into the Earth's atmosphere during periods of strong southward IMF B z , which preferentially provides a source of free energy for electromagnetic ion cyclotron (EMIC) wave excitation. This is supported by the fact that the strongest electron precipitation into the atmosphere is found in the dusk sector, where EMIC waves are typically observed in the high‐density plasmasphere or plume and cause efficient electron precipitation down to ~1 MeV.