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Relation Between Shock‐Related Impulse and Subsequent ULF Wave in the Earth's Magnetosphere
Author(s) -
Zhang Dianjun,
Liu Wenlong,
Li Xinlin,
Sarris Theodore E.,
Wang Yongfu,
Xiao Chao,
Zhang Zhao,
Wygant John R.
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 - 10.1029/2020gl090027
Subject(s) - magnetosphere , physics , impulse (physics) , amplitude , geophysics , shock wave , interplanetary spaceflight , ultra low frequency , computational physics , acoustics , solar wind , mechanics , magnetic field , classical mechanics , optics , quantum mechanics
Abstract The generation of Pc4‐5 ultralow frequency (ULF) waves after interplanetary shock‐induced electric field impulses in the Earth's magnetosphere is studied using Van Allen Probes measurements by investigating the relationship between the first impulses and subsequent resonant ULF waves. In the dayside, the relevant time scales of the first impulse is correlated better with local Alfvén speed than with local eigenfrequency, implying that the temporal scale of the first impulse is more likely related to fast‐mode wave propagation rather than local field line resonance. There are only 20 out of 51 events with narrow‐band poloidal ULF waves induced after the first impulse, showing a higher chance for ULF wave generation at the locations where the impulse equivalent frequency scale matches the local eigenfrequency. It is suggested that the shock‐related ULF wave can be excited in the magnetosphere on condition that shock‐induced impulse has large enough amplitude with its frequency matching the local eigenfrequency.