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Statistical Study of Energetic Electron Butterfly Pitch Angle Distributions During Magnetic Dip Events
Author(s) -
Xiong Ying,
Xie Lun,
Fu Suiyan,
Pu Zuyin
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl085091
Subject(s) - pitch angle , physics , electron , magnetic dip , butterfly , van allen radiation belt , magnetosphere , earth's magnetic field , magnetic field , astrophysics , geophysics , nuclear physics , finance , quantum mechanics , economics
The magnetic dips can create the electron butterfly pitch angle distribution (PAD) in the inner magnetosphere. However, its universality is still unconfirmed. We statistically investigate the global distribution of the occurrence rate of the magnetic dip‐related butterfly PAD for 466 keV and 2.1 MeV electrons using the measurements of the twin Van Allen Probes spanning from September 2012 to November 2018. The statistical results show that the magnetic dip‐related butterfly PADs are mainly confined to duskside to midnight within 4.5 < L < 6, and the peak occurrence rate (30% for 466 KeV and 70% for 2.1 MeV) occurs at the duskside equator around L = 5. The parametric study results suggest that the butterfly PADs preferably occur for high energy electrons with a negative initial radial flux gradient and a nearly isotropic initial PAD, which is consistent with the statistic results. This work confirms the vital importance of the magnetic dips on the evolution of the electron PADs.