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New evidence for generation mechanisms of discrete and hiss‐like whistler mode waves
Author(s) -
Gao Xinliang,
Li Wen,
Thorne Richard M.,
Bortnik Jacob,
Angelopoulos Vassilis,
Lu Quanming,
Tao Xin,
Wang Shui
Publication year - 2014
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 - 10.1002/2014gl060707
Subject(s) - hiss , chorus , amplitude , physics , falling (accident) , computational physics , range (aeronautics) , waveform , tone (literature) , meteorology , electron , nuclear physics , quantum mechanics , materials science , medicine , art , literature , environmental health , voltage , composite material
Linear theory suggests that whistler mode wave growth rates are proportional to the ratio of hot electron (~1 to 30 keV) density to total electron density ( N h / N t ), whereas nonlinear wave theory suggests that an optimum linear growth rate is required to generate rising tone chorus from hiss‐like emissions. Using the Time History of Events and Macroscale Interactions during Substorms waveform data collected by three probes over the past ~5 years, we investigate the correlation between N h / N t and wave amplitude/wave occurrence rate for rising tone, falling tone, and hiss‐like emissions separately. Statistical results show that the rising and falling tones preferentially occur in the region with a limited N h / N t range, whereas both the occurrence rate and wave amplitudes of hiss‐like emissions become larger for higher values of N h / N t . Our statistical results not only provide an important clue on the generation mechanism of hiss‐like emissions, but also provide supporting experimental evidence for the nonlinear theory of generating rising tone chorus.