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Near‐Earth injection of MeV electrons associated with intense dipolarization electric fields: Van Allen Probes observations
Author(s) -
Dai Lei,
Wang Chi,
Duan Suping,
He Zhaohai,
Wygant John R.,
Cattell Cynthia A.,
Tao Xin,
Su Zhenpeng,
Kletzing Craig,
Baker Daniel N.,
Li Xinlin,
Malaspina David,
Blake J. Bernard,
Fennell Joseph,
Claudepierre Seth,
Turner Drew L.,
Reeves Geoffrey D.,
Funsten Herbert O.,
Spence Harlan E.,
Angelopoulos Vassilis,
Fruehauff Dennis,
Chen Lunjin,
Thaller Scott,
Breneman Aaron,
Tang Xiangwei
Publication year - 2015
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 - 10.1002/2015gl064955
Subject(s) - substorm , physics , van allen radiation belt , electron , atomic physics , electric field , magnetosphere , van allen probes , nuclear physics , plasma , quantum mechanics
Abstract Substorms generally inject tens to hundreds of keV electrons, but intense substorm electric fields have been shown to inject MeV electrons as well. An intriguing question is whether such MeVelectron injections can populate the outer radiation belt. Here we present observations of a substorm injection of MeV electrons into the inner magnetosphere. In the premidnight sector at L ∼ 5.5, Van Allen Probes (Radiation Belt Storm Probes)‐A observed a large dipolarization electric field (50 mV/m) over ∼40 s and a dispersionless injection of electrons up to ∼3 MeV. Pitch angle observations indicated betatron acceleration of MeV electrons at the dipolarization front. Corresponding signals of MeV electron injection were observed at LANL‐GEO, THEMIS‐D, and GOES at geosynchronous altitude. Through a series of dipolarizations, the injections increased the MeV electron phase space density by 1 order of magnitude in less than 3 h in the outer radiation belt ( L > 4.8). Our observations provide evidence that deep injections can supply significant MeV electrons.