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Electron Flux Enhancements at L = 4.2 Observed by Global Positioning System Satellites: Relationship With Solar Wind and Geomagnetic Activity
Author(s) -
Zhang XiaoJia,
Mourenas Didier,
Artemyev Anton V.,
Angelopoulos Vassilis,
Thorne Richard Mansergh
Publication year - 2018
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2018ja025497
Subject(s) - plasmasphere , physics , solar wind , van allen radiation belt , flux (metallurgy) , van allen probes , earth's magnetic field , electron , geomagnetic storm , space weather , geophysics , computational physics , atmospheric sciences , magnetosphere , magnetic field , plasma , nuclear physics , chemistry , organic chemistry , quantum mechanics
Determining solar wind and geomagnetic activity parameters most favorable to strong electron flux enhancements is an important step toward forecasting radiation belt dynamics. Using electron flux measurements from Global Positioning System satellites at L = 4.2 in 2009–2016, we seek statistical relationships between flux enhancements at different energies and solar wind dynamic pressure P dyn , A E , and K p , from hundreds of events inside and outside the plasmasphere. Most ≥1‐MeV electron flux enhancements occur during nonstorm (or weak storm) times. Flux enhancements of 4‐MeV electrons outside the plasmasphere occur during periods of low P dyn and high A E . We perform superposed epoch analyses of Global Positioning System electron fluxes, along with solar wind and geomagnetic indices, 40‐keV electron flux, ultralow frequency (ULF) wave index from Geostationary Operational Environmental Satellite, and chorus wave intensity from the Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms mission. We demonstrate that 4‐MeV electron flux enhancements outside the plasmasphere start when the interplanetary magnetic field ( B z ) reaches a minimum and develop during periods of low P dyn , high A E , low but increasing D s t , moderate ULF wave index, and intense chorus waves. Flux enhancements at 100 keV occur under conditions with higher P dyn , higher ULF wave index, and elevated 40‐keV electron flux at L = 6.6. Moreover, electron flux enhancements take much more time to develop at higher energies. This suggests that 100‐keV flux enhancements are dominated by injections, while MeV electron energization is predominantly induced by chorus waves with further amplification by inward transport.