Premium
Generation of extremely low frequency chorus in Van Allen radiation belts
Author(s) -
Xiao Fuliang,
Liu Si,
Tao Xin,
Su Zhenpeng,
Zhou Qinghua,
Yang Chang,
He Zhaoguo,
He Yihua,
Gao Zhonglei,
Baker D. N.,
Spence H. E.,
Reeves G. D.,
Funsten H. O.,
Blake J. B.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023561
Subject(s) - chorus , van allen radiation belt , physics , electron , van allen probes , pitch angle , saturn , magnetosphere , jupiter (rocket family) , computational physics , population , radiation , relativistic particle , planet , plasma , atomic physics , astrophysics , geophysics , astronomy , nuclear physics , spacecraft , art , literature , demography , sociology
Recent studies have shown that chorus can efficiently accelerate the outer radiation belt electrons to relativistic energies. Chorus, previously often observed above 0.1 equatorial electron gyrofrequency f ce , was generated by energetic electrons originating from Earth's plasma sheet. Chorus below 0.1 f ce has seldom been reported until the recent data from Van Allen Probes, but its origin has not been revealed so far. Because electron resonant energy can approach the relativistic level at extremely low frequency, relativistic effects should be considered in the formula for whistler mode wave growth rate. Here we report high‐resolution observations during the 14 October 2014 small storm and firstly demonstrate, using a fully relativistic simulation, that electrons with the high‐energy tail population and relativistic pitch angle anisotropy can provide free energy sufficient for generating chorus below 0.1 f ce . The simulated wave growth displays a very similar pattern to the observations. The current results can be applied to Jupiter, Saturn, and other magnetized planets.