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Large‐Amplitude Electromagnetic Ion Cyclotron Waves and Density Fluctuations in the Flank of the Earth's Magnetosheath
Author(s) -
Zhao J. S.,
Wang T. Y.,
Dunlop M. W.,
Shi C.,
He J. S.,
Dong X. C.,
Wu D. J.,
Giles B.,
Russell C. T.
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 - 10.1029/2019gl081964
Subject(s) - magnetosheath , physics , amplitude , cyclotron , magnetosphere , magnetic field , computational physics , geophysics , instability , atomic physics , electron , astrophysics , magnetopause , optics , nuclear physics , quantum mechanics , mechanics
Abstract The electromagnetic ion cyclotron (EMIC) wave usually observed in the Earth's magnetosheath is thought to be generated through the ion temperature anisotropy instability. This paper presents an observation of a long‐lasting large‐amplitude EMIC wave event in the dawnside flank of the magnetosheath by the Magnetospheric Multiscale mission, lasting from 06:33:00 to 12:35:00 UT on 16 April 2018. The wave amplitude is around 0.2 nT as compared to the ambient magnetic field ~ 12 nT. The characteristic frequency and scale size are around 0.2 Hz and 1,028 km, respectively. Accompanying EMIC waves are density fluctuations, which exhibit both positive and negative correlations with the longitudinal magnetic field. Using the fitted parameters for the ion and electron phase space densities, plasma kinetic theory predicts local excitations of both EMIC and mirror instabilities, which provide the energy of these observed EMIC waves and density fluctuations.