Abstract We study the dynamics of radiation belt electrons during a 10-day quiet period perturbed by substorm activity and preceding a high-speed stream (HSS), aiming at a global description of the radiation belts in L-shell, L in [2, 6], and energy [0.1, 10] MeV. We combine Van Allen Probes observations and Fokker-Planck numerical simulations of pitch-angle diffusion. The Fokker-Planck model uses event-driven pitch angle diffusion coefficients from whistler-mode waves, built from the wave properties and the ambient plasma density measurements from the Van Allen Probes. We first find this event has some similar characteristics to regular quiet times previously studied; a widely extended plasmasphere within which we observe strong and varying whistler-mode waves. These ambient conditions lead to strong pitch-angle scattering, which contributes to the creation of a wide slot region as well as a significant decay of the outer radiation belts, which are observed and qualitatively well simulated. In addition, we find the substorm activity causes short duration (within ± 4h) decay of the plasma density and a lowering amplitude of the whistler-mode waves within the plasmasphere, both causing opposite effects in terms of pitch angle diffusion. This leads to a diminution of pitch-angle diffusion at the time of the main substorm activity. Conversely, whistler-mode waves become enhanced in the time periods between the substorm injections. All effects cumulated, we find an enhancement of pitch angle diffusion by whistler-mode waves above L∼4.7 during the 10-day period. This directly relates to the combination of quietness and substorm activity which allows pitch angle diffusing of up to 1 MeV electrons in the outer belt. Relativistic electrons of 1–2 MeV remain trapped in the outer belt, from L∼4.7 to L∼5.2, forming, in both the observations and the simulations, a distinct pocket of remnant electrons.

中文翻译：

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在亚暴活动扰动的安静时期被哨声模式波散射

摘要 我们研究了受亚暴活动扰动和高速流 (HSS) 之前的 10 天安静期辐射带电子的动力学，旨在对 L 壳层中的辐射带进行全局描述，L 在 [2, 6] 和能量 [0.1, 10] MeV。我们结合了 Van Allen Probes 观测和 Fokker-Planck 俯仰角扩散数值模拟。Fokker-Planck 模型使用来自惠斯勒模式波的事件驱动的俯仰角扩散系数，该系数是根据波特性和范艾伦探测器的环境等离子体密度测量建立的。我们首先发现这个事件与之前研究的常规安静时间有一些相似的特征；一个广泛扩展的等离子层，我们在其中观察到强烈且变化的哨声模式波。这些环境条件导致强烈的俯仰角散射，这有助于产生一个宽阔的狭缝区域以及外部辐射带的显着衰减，这些都被观察到并在质量上得到了很好的模拟。此外，我们发现亚暴活动导致等离子体密度的短时间（±4 小时内）衰减和等离子体层内惠斯勒模式波的振幅降低，两者在俯仰角扩散方面造成相反的影响。这导致主亚暴活动发生时俯仰角扩散的减少。相反，在亚暴注入之间的时间段内，惠斯勒模式波会增强。累积所有影响，我们发现在 10 天期间，L∼4.7 以上的哨声模式波增强了俯仰角扩散。这与安静和亚暴活动的结合直接相关，这允许外带中高达 1 MeV 电子的俯仰角扩散。1-2 MeV 的相对论电子仍然被困在外带中，从 L∼4.7 到 L∼5.2，在观察和模拟中形成了一个独特的残余电子袋。