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 disperse...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.展开更多
We study the Landau resonance between geodesic acoustic mode（GAM） and trapped electrons as a GAM’s collisionless damping. The assumption of ˉωde 〈〈ωbeis adopted.The damping rate induced by trapped electrons is...We study the Landau resonance between geodesic acoustic mode（GAM） and trapped electrons as a GAM’s collisionless damping. The assumption of ˉωde 〈〈ωbeis adopted.The damping rate induced by trapped electrons is found to be an increasing function of q. In low q range, circulating-ion-induced damping rate is larger than that induced by trapped electrons.As q increases, the latter becomes larger than the former. The reason is that trapped electrons’ resonant velocity is close to vtefrom the lower side, whiles circulating ions’ resonant velocity gets bigger further from vti. So the number of resonant trapped electrons increases, whiles the number of resonant circulating ions decreases. The amplitude of damping rate induced by trapped electrons in the edge plasma can be comparable to that induced by circulating ions in the low q range.Another phenomenon we found is that in the chosen range of, the damping caused by trapped electrons has a maximum value at point εq for different q. The reason is that as is close to q,trapped electorns’ resonant velocity is close to vte.展开更多
基金supported by National Natural Science Foundation of China National Natural Science Foundation of China (41421003 and 41627805)
文摘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.
文摘We study the Landau resonance between geodesic acoustic mode（GAM） and trapped electrons as a GAM’s collisionless damping. The assumption of ˉωde 〈〈ωbeis adopted.The damping rate induced by trapped electrons is found to be an increasing function of q. In low q range, circulating-ion-induced damping rate is larger than that induced by trapped electrons.As q increases, the latter becomes larger than the former. The reason is that trapped electrons’ resonant velocity is close to vtefrom the lower side, whiles circulating ions’ resonant velocity gets bigger further from vti. So the number of resonant trapped electrons increases, whiles the number of resonant circulating ions decreases. The amplitude of damping rate induced by trapped electrons in the edge plasma can be comparable to that induced by circulating ions in the low q range.Another phenomenon we found is that in the chosen range of, the damping caused by trapped electrons has a maximum value at point εq for different q. The reason is that as is close to q,trapped electorns’ resonant velocity is close to vte.
