An Event on Simultaneous Amplification of Exohiss and Chorus Waves Associated With Electron Density Enhancements.

Autor: Zhu, Hui1,2 zhuhui328@gmail.com, Shprits, Yuri Y.2,3,4, Chen, Lunjin1, Liu, Xu1, Kellerman, Adam C.2
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Zdroj: Journal of Geophysical Research. Space Physics. Nov2018, Vol. 123 Issue 11, p8958-8968. 11p.
Abstrakt: Whistler mode exohiss are the structureless hiss waves observed outside the plasmapause with featured equatorward Poynting flux. An event of the amplification of exohiss as well as chorus waves was recorded by Van Allen Probes during the recovery phase of a weak geomagnetic storm. Amplitudes of both types of the waves showed a significant increase at the regions of electron density enhancements. It is found that the electrons resonant with exohiss and chorus showed moderate pitch angle anisotropies. The ratio of the number of electrons resonating with exohiss to total electron number presented in‐phase correlation with density variations, which suggests that exohiss can be amplified due to electron density enhancement in terms of cyclotron instability. The calculation of linear growth rates further supports above conclusion. We suggest that exohiss waves have potential to become more significant due to the background plasma fluctuation. Key Points: Simultaneous amplification of chorus and exohiss is observed by Van Allen ProbesThe plasma analysis of RBSPICE and HOPE suggests that the enhancement of electron number density accounts for the wave amplificationThe calculation of growth rate based on linear theory verifies the importance of density [ABSTRACT FROM AUTHOR]
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