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Observational evidence of the generation mechanism for rising‐tone chorus
Author(s) -
Cully C. M.,
Angelopoulos V.,
Auster U.,
Bonnell J.,
Le Contel O.
Publication year - 2011
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 - 10.1029/2010gl045793
Subject(s) - magnetosphere , chorus , physics , cyclotron resonance , amplitude , computational physics , geophysics , cyclotron , whistler , van allen radiation belt , charged particle , electron , plasma , optics , ion , quantum mechanics , art , literature
Chorus emissions are a striking feature of the electromagnetic wave environment in the Earth's magnetosphere. These bursts of whistler‐mode waves exhibit characteristic frequency sweeps (chirps) believed to result from wave‐particle trapping of cyclotron‐resonant particles. Based on the theory of Omura et al. (2008), we predict the sweep rates of chorus elements observed by the THEMIS satellites. The predictions use independent observations of the electron distribution functions and have no free parameters. The predicted chirp rates are a function of wave amplitude, and this relation is clearly observed. The predictive success of the theory lends strong support to its underlying physical mechanism: cyclotron‐resonant wave‐particle trapping.