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Van Allen Probes observations of whistler‐mode chorus with long‐lived oscillating tones
Author(s) -
Gao Zhonglei,
Su Zhenpeng,
Chen Lunjin,
Zheng Huinan,
Wang Yuming,
Wang Shui
Publication year - 2017
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 - 10.1002/2017gl073420
Subject(s) - chorus , hiss , physics , van allen probes , whistler , tone (literature) , spectrogram , van allen radiation belt , oscillation (cell signaling) , astrophysics , magnetosphere , electron , plasma , art , literature , quantum mechanics , computer science , computer vision , biology , genetics
Whistler‐mode chorus plays an important role in the radiation belt electron dynamics. In the frequency‐time spectrogram, chorus often appears as a hiss‐like band and/or a series of short‐lived (up to ∼1 s) discrete elements. Here we present some rarely reported chorus emissions with long‐lived (up to 25 s) oscillating tones observed by the Van Allen Probes in the dayside (MLT ∼9–14) midlatitude (|MLAT|>15°) region. An oscillating tone can behave either regularly or irregularly and can even transform into a nearly constant tone (with a relatively narrow frequency sweep range). We suggest that these highly coherent oscillating tones were generated naturally rather than being related to some artificial VLF transmitters. Possible scenarios for the generation of the oscillating tone chorus are as follows: (1) being nonlinearly triggered by the accompanying hiss‐like bands or (2) being caused by the modulation of the wave source. The details of the generation and evolution of such a long‐lived oscillating tone chorus need to be investigated both theoretically and experimentally in the future.