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Observational evidence of the excitation of magnetosonic waves by an He++ ion ring distribution
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  • Seth G. Claudepierre,
  • Xu Liu,
  • Lunjin Chen,
  • Kazue Takahashi
Seth G. Claudepierre

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Xu Liu
University of Texas at Dallas, Willian B. Hansen Center for Space Sciences
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Lunjin Chen
University of Texas at Dallas
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Kazue Takahashi
The Johns Hopkins University Applied Physics Laboratory
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We report plasma wave observations of equatorial magnetosonic waves at integer harmonics of the local gyrofrequency of doubly-ionized helium (He++). The waves were observed by Van Allen Probe A on 08 Feb 2014 when the spacecraft was in the afternoon magnetic local time sector near L ≈ 4 inside of the plasmasphere. Analysis of the complementary in-situ energetic ion measurements (1-300 keV) reveals the presence of a helium ion ring distribution centered near 30 keV. Theoretical linear growth rate calculations suggest that the local plasma and field conditions can support the excitation of the magnetosonic waves from the unstable ring distribution. This represents the first report of the generation of magnetosonic equatorial noise via a ring distribution in energetic He++ ions in the near-Earth space plasma environment.
Aug 2021Published in Journal of Geophysical Research: Space Physics volume 126 issue 8. 10.1029/2021JA029532