Corotating drift-bounce resonance of plasmaspheric electron with poloidal ULF waves  

作　　者：Qiu-Gang Zong YongFu Wang Jie Ren XuZhi Zhou SuiYan Fu Robert Rankin Hui Zhang 

机构地区：[1]Institute of Space Physics and Applied Technology, Peking University [2]Department of Physics, University of Alberta [3]Physics Department and Geophysical Institute, University of Alaska Fairbanks

出　　处：《Earth and Planetary Physics》2017年第1期2-12,共11页地球与行星物理（英文版）

基　　金：supported by National Natural Science Foundation of China National Natural Science Foundation of China (41421003 and 41627805)

摘　　要：The purpose of this paper is to understand how low energy plasmaspheric electrons respond to ULF waves excited by interplanetary shocks impinging on magnetosphere. It is found that both energy and pitch angle dispersed plasmaspheric electrons with energy of a few eV to tens of eV can be generated simultaneously by the interplanetary shock. The subsequent period of successive dispersion signatures is around 40 s and is consistent with the ULF wave period(third harmonic). By tracing back the energy and pitch angle dispersion signatures, the position of the electron injection region is found to be off-equator at around -32° in the southern hemisphere. This can be explained as the result of injected electrons being accelerated by higher harmonic ULF waves(e.g. third harmonic) which carry a larger amplitude electric field off-equator. The dispersion signatures are due to the flux modulations(or accelerations) of " local" plasmaspheric electrons rather than electrons from the ionosphere. With the observed wave-borne large electric field excited by the interplanetary shock impact, the kinetic energy can increase to a maximum of 23 percent in one bouncing cycle for plasmaspheric electrons satisfying the drift-bounce resonance condition by taking account of both the corotating drift and bounce motion of the local plasmaspheric electron.The purpose of this paper is to understand how low energy plasmaspheric electrons respond to ULF waves excited byinterplanetary shocks impinging on magnetosphere. It is found that both energy and pitch angle dispersed plasmaspheric electrons withenergy of a few eV to tens of eV can be generated simultaneously by the interplanetary shock. The subsequent period of successivedispersion signatures is around 40 s and is consistent with the ULF wave period （third harmonic）. By tracing back the energy and pitchangle dispersion signatures, the position of the electron injection region is found to be off-equator at around –32° in the southernhemisphere. This can be explained as the result of injected electrons being accelerated by higher harmonic ULF waves （e.g. thirdharmonic） which carry a larger amplitude electric field off-equator. The dispersion signatures are due to the flux modulations （oraccelerations） of ＂ local” plasmaspheric electrons rather than electrons from the ionosphere. With the observed wave-borne large electricfield excited by the interplanetary shock impact, the kinetic energy can increase to a maximum of 23 percent in one bouncing cycle forplasmaspheric electrons satisfying the drift-bounce resonance condition by taking account of both the corotating drift and bouncemotion of the local plasmaspheric electron.

关 键 词：drift-bounce resonance plasmaspheric electron poloidal mode ULF wave 

分 类 号：P354[天文地球—空间物理学]