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Statistical Evidence for EMIC Wave Excitation Driven by Substorm Injection and Enhanced Solar Wind Pressure in the Earth's Magnetosphere: Two Different EMIC Wave Sources
Author(s) -
Chen Huayue,
Gao Xinliang,
Lu Quanming,
Tsurutani Bruce T.,
Wang Shui
Publication year - 2020
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 - 10.1029/2020gl090275
Subject(s) - substorm , magnetosphere , physics , geophysics , solar wind , van allen probes , noon , astrophysics , ring current , emic and etic , plasmasphere , local time , plasma sheet , atmospheric sciences , van allen radiation belt , plasma , nuclear physics , sociology , anthropology , statistics , mathematics
Substorm injection and solar wind dynamic pressure have long been considered as two main drivers of electromagnetic ion cyclotron (EMIC) wave excitation, but clear observational evidence is still lacking. With Van Allen Probes data from 2012–2017, we have investigated the roles of the two EMIC wave drivers separately, by using time‐modified AE + and P d + . Both the occurrence rate and magnetic amplitude of waves significantly increase with the enhancement of each index. During large AE + , EMIC waves are mainly generated in the dusk sector (16 ≤ MLT ≤ 20) and near the magnetic equator ( |MLAT| < 10° ). This is presumably due to substorm‐injected protons drifting from midnight sector to the plasmaspheric bulge. While during large P d + , EMIC waves mainly occur in the noon sector (9 ≤ MLT ≤ 15). But there exist higher‐latitude ( 10° < |MLAT| < 20° ) source regions besides equatorial source, possibly due to the minimum B regions. Our results provide strong observational support to existing generation mechanisms of EMIC waves in the Earth's magnetosphere.