On the Association Between Electron Flux Oscillations and Local Phase Space Density Gradients
On the Association Between Electron Flux Oscillations and Local Phase Space Density Gradients
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DOI：
10.1029/2020ja028891
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发表时间：
2021-02
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影响因子：
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通讯作者：
T. Sarris;Xinlin Li;Hong Zhao;L. Khoo;Wenlong Liu;M. Temerin
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作者：
T. Sarris;Xinlin Li;Hong Zhao;L. Khoo;Wenlong Liu;M. Temerin
在10keV到100keV范围内的电子能量通道中经常观察到电子通量振荡。它们以通量波动的形式被观测到，其周期与地球周围电子的漂移周期相对应，并可由于与宽带超低频(ULF)波的漂移共振相互作用而在磁层中产生。它们特别是在平静时间观察到的，是正在进行的漂移-共振过程和由此产生的由超低频波引起的径向传输的指标。在这项研究中，我们研究了这种磁通振荡的出现与局域相空间密度之间的关系。特别是，当存在非零相空间密度梯度时，磁通振荡就会出现，而且观测到的磁通振荡幅度与径向相空间密度梯度有关，梯度越陡，磁通振荡的幅度就越大。通过在L*∼5到∼5.6的远地点对范艾伦探测器双航天器飞行任务的统计观测发现，在平静时期，对于∼400keV的电子能量，电子通量振荡更有可能减弱，而对于相应的∼300 MeV/G的第一绝热不变量，相空间密度更有可能为零。
Electron flux oscillations are often observed in electron energy channels in the range of 10 keV to 100 keV. They are observed in the form of flux fluctuations with periods corresponding to the drift periods of electrons around the Earth and can be produced in the magnetosphere as a result of drift resonant interactions in association with broadband ultra‐low frequency (ULF) waves. They are observed in particular during quiet times and are indicators of ongoing drift‐resonant processes and resulting radial transport caused by ULF waves. In this study we investigate the association of the appearance of such flux oscillations with the local phase space density. In particular, it is shown that flux oscillations appear when nonzero phase space density gradients are present and furthermore that the observed amplitude of flux oscillations is dependent on radial phase space density gradients, with steeper gradients enabling the observation of flux oscillations with higher‐amplitude. Via statistical observations from the Van Allen probes twin‐spacecraft mission while at apogee at L* ∼5 to ∼5.6 it is found that, during quiet times, electron flux oscillations are more likely to diminish for electron energy of ∼400 keV, and associated phase space density is more likely to be zero for the corresponding first adiabatic invariant values of ∼300 MeV/G. It is also concluded that flux oscillations could be used as indicators of phase space density gradients.