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Statistical distribution of EMIC wave spectra: Observations from Van Allen Probes
Author(s) -
Zhang X.J.,
Li W.,
Thorne R. M.,
Angelopoulos V.,
Bortnik J.,
Kletzing C. A.,
Kurth W. S.,
Hospodarsky G. B.
Publication year - 2016
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 - 10.1002/2016gl071158
Subject(s) - physics , emic and etic , van allen radiation belt , cyclotron , computational physics , spectral line , scattering , amplitude , atomic physics , electron , van allen probes , plasma , optics , nuclear physics , astronomy , magnetosphere , sociology , anthropology
It has been known that electromagnetic ion cyclotron (EMIC) waves can precipitate ultrarelativistic electrons through cyclotron resonant scattering. However, the overall effectiveness of this mechanism has yet to be quantified, because it is difficult to obtain the global distribution of EMIC waves that usually exhibit limited spatial presence. We construct a statistical distribution of EMIC wave frequency spectra and their intensities based on Van Allen Probes measurements from September 2012 to December 2015. Our results show that as the ratio of plasma frequency over electron gyrofrequency increases, EMIC wave power becomes progressively dominated by the helium band. There is a pronounced dawn‐dusk asymmetry in the wave amplitude and the frequency spectrum. The frequency spectrum does not follow the commonly used single‐peak Gaussian function. Incorporating these realistic EMIC wave frequency spectra into radiation belt models is expected to improve the quantification of EMIC wave scattering effects in ultrarelativistic electron dynamics.