Electron Scattering by Plasmaspheric Hiss in a Nightside Plume
Electron Scattering by Plasmaspheric Hiss in a Nightside Plume
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夜侧羽流中等离子体球嘶嘶声的电子散射
DOI：
10.1029/2018gl077212
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发表时间：
2018
影响因子：
5.2
通讯作者：
Hua Man
中科院分区：
文献类型：
--
作者：
Zhang Wenxun;Fu Song;Gu Xudong;Ni Binbin;Xiang Zheng;Summers Danny;Zou Zhengyang;Cao Xing;Lou Yuequn;Hua Man
等离子体层嘶嘶声在高等离子体密度区的辐射带电子动力学中起着重要的作用。2012年12月26日，货车艾伦探测器观测到了两次等离子体层羽流穿越，这两次穿越发生在地磁平静期L4 -6之间的午夜至黎明扇区。该羽流显示出明显的电子密度高于平均羽流水平。中等嘶嘶声排放伴随着两个羽流交叉，峰值功率约为100 Hz。通过羽流中的嘶嘶声对准线性反弹平均电子散射率的量化表明，波在损失锥附近以高达~10−4 s−1的速率有效地散射~10-100 keV的电子，但对散射更高能量的电子数量逐渐变得不重要。由于夜侧羽流中的嘶嘶声而导致的电子损失的时间尺度随着电子动能的变化而变化很大，超过3个数量级，也就是说，从几十keV电子的几个小时到几百keV电子的几天，再到>1 MeV电子的100天以上。这些电子损失时间尺度随L-壳层和嘶嘶声光谱强度的多四分位数分布略有变化，表明夜侧羽流中的嘶嘶声排放是100 keV电子快速损失和高能电子缓慢衰减的可行候选者。
Plasmaspheric hiss is known to play an important role in radiation belt electron dynamics in high plasma density regions. We present observations of two crossings of a plasmaspheric plume by the Van Allen Probes on 26 December 2012, which occurred unusually at the post‐midnight‐to‐dawn sector between L ~ 4–6 during a geomagnetically quiet period. This plume exhibited pronounced electron densities higher than those of the average plume level. Moderate hiss emissions accompanied the two plume crossings with the peak power at about 100 Hz. Quantification of quasi‐linear bounce‐averaged electron scattering rates by hiss in the plume demonstrates that the waves are efficient to pitch angle scatter ~10–100 keV electrons at rates up to ~10−4 s−1 near the loss cone but become gradually insignificant to scatter the higher energy electron population. The resultant timescales of electron loss due to hiss in the nightside plume vary largely with electron kinetic energy over 3 orders of magnitude, that is, from several hours for tens of keV electrons to a few days for hundreds of keV electrons to well above 100 days for >1 MeV electrons. Changing slightly with L‐shell and the multiquartile profile of hiss spectral intensity, these electron loss timescales suggest that hiss emissions in the nightside plume act as a viable candidate for the fast loss of the ≲100 keV electrons and the slow decay of higher energy electrons.