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Characteristics and Generation of Low‐Frequency Magnetosonic Waves Below the Proton Gyrofrequency
Author(s) -
Teng Shangchun,
Li Wen,
Tao Xin,
Ma Qianli,
Shen Xiaochen
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 - 10.1029/2019gl085372
Subject(s) - plasmasphere , physics , van allen probes , magnetosphere , van allen radiation belt , amplitude , proton , cyclotron , equator , geophysics , earth's magnetic field , ultra low frequency , computational physics , magnetic field , plasma , nuclear physics , latitude , optics , astronomy , quantum mechanics
We report a Van Allen Probes observation of large‐amplitude magnetosonic waves with the peak intensity below the proton gyrofrequency ( f cp ), which may potentially be misinterpreted as electromagnetic ion cyclotron waves. The frequency spacing of the wave harmonic structure suggests that these magnetosonic waves are excited at a distant source region and propagate radially inward. We also conduct a statistical analysis of low‐frequency magnetosonic waves below f cp based on the Van Allen Probes data from October 2012 to December 2018. The spatial distribution shows that these low‐frequency magnetosonic emissions are dominantly observed inside the plasmasphere from the prenoon to the midnight sector within 5° of the geomagnetic equator and typically have modest‐to‐strong wave amplitudes ranging from tens of pT to hundreds of pT. Our study provides insight into understanding the generation and propagation of these low‐frequency magnetosonic waves in the Earth's inner magnetosphere.