Resonant scattering of outer zone relativistic electrons by multiband EMIC waves and resultant electron loss time scales

To improve our understanding of the role of electromagnetic ion cyclotron (EMIC) waves in radiation belt electron dynamics, we perform a comprehensive analysis of EMIC wave‐induced resonant scattering of outer zone relativistic (>0.5 MeV) electrons and resultant electron loss time scales with res...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2015-09, Vol.120 (9), p.7357-7373
Main Authors: Ni, Binbin, Cao, Xing, Zou, Zhengyang, Zhou, Chen, Gu, Xudong, Bortnik, Jacob, Zhang, Jichun, Fu, Song, Zhao, Zhengyu, Shi, Run, Xie, Lun
Format: Article
Language:English
Subjects:
Amplitudes
Decay
Diffusion
Dynamics
electron loss time scales
Electrons
EMIC waves
Geophysics
outer radiation belt
Pitch angle
relativistic electrons
resonant wave-particle interactions
Resultants
Scattering
Time
Wave scattering
Waves
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Summary:To improve our understanding of the role of electromagnetic ion cyclotron (EMIC) waves in radiation belt electron dynamics, we perform a comprehensive analysis of EMIC wave‐induced resonant scattering of outer zone relativistic (>0.5 MeV) electrons and resultant electron loss time scales with respect to EMIC wave band, L shell, and wave normal angle model. The results demonstrate that while H+‐band EMIC waves dominate the scattering losses of ~1–4 MeV outer zone relativistic electrons, it is He+‐band and O+‐band waves that prevail over the pitch angle diffusion of ultrarelativistic electrons at higher energies. Given the wave amplitude, EMIC waves at higher L shells tend to resonantly interact with a larger population of outer zone relativistic electrons and drive their pitch angle scattering more efficiently. Obliquity of EMIC waves can reduce the efficiency of wave‐induced relativistic electron pitch angle scattering. Compared to the frequently adopted parallel or quasi‐parallel model, use of the latitudinally varying wave normal angle model produces the largest decrease in H+‐band EMIC wave scattering rates at pitch angles  ~5 MeV. At a representative nominal amplitude of 1 nT, EMIC wave scattering produces the equilibrium state (i.e., the lowest normal mode under which electrons at the same energy but different pitch angles decay exponentially on the same time scale) of outer belt relativistic electrons within several to tens of minutes and the following exponential decay extending to higher pitch angles on time scales from
ISSN:2169-9380
2169-9402
DOI:10.1002/2015JA021466