Van Allen Probes Observations of Multi‐MeV Electron Drift‐Periodic Flux Oscillations in Earth's Outer Radiation Belt During the March 2017 Event
Van Allen Probes Observations of Multi‐MeV Electron Drift‐Periodic Flux Oscillations in Earth's Outer Radiation Belt During the March 2017 Event
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DOI：
10.1029/2021ja029284
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发表时间：
2021-07
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通讯作者：
Hong Zhao;T. Sarris;Xinlin Li;Max Weiner;Isabela Huckabee;D. Baker;A. Jaynes;S. Kanekal;S. Elkington;M. Barani;W. Tu;Wenlong Liu;Dianjun Zhang;M. Hartinger
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作者：
Hong Zhao;T. Sarris;Xinlin Li;Max Weiner;Isabela Huckabee;D. Baker;A. Jaynes;S. Kanekal;S. Elkington;M. Barani;W. Tu;Wenlong Liu;Dianjun Zhang;M. Hartinger
辐射带电子在各种物理机制下经历频繁的加速、传输和损失过程。最普遍的机制之一是径向扩散，它是由 Pc4-5 波段的高能电子和 ULF 波之间的共振相互作用引起的。这种共振相互作用的一个表现被认为是周期性通量振荡的出现。在这项研究中，我们报告了范艾伦探测器任务观测到的外辐射带中能量高达 ~7.7 MeV 的相对论和超相对论电子的长期漂移周期通量振荡。在2017年3月的这次事件中，电子漂移频率下的多MeV电子通量振荡与增强的Pc5 ULF波活动同时出现，并在外带中心持续了10多个小时。这种通量振荡的幅度与电子相空间密度（PSD）的径向梯度密切相关，在 PSD 峰值附近几乎没有观察到振荡。 PSD 径向剖面的时间演化也表明了在此事件期间径向扩散在多 MeV 电子动力学中的主导作用。通过结合这些观察结果，我们得出结论，这些多 MeV 电子通量振荡是由电子和宽带 Pc5 ULF 波之间的共振相互作用引起的，并且是该事件期间正在进行的径向扩散过程的指标。它们包含径向扩散的基本信息，并有可能进一步用于量化径向扩散效应并帮助更好地理解这种普遍机制。
Radiation belt electrons undergo frequent acceleration, transport, and loss processes under various physical mechanisms. One of the most prevalent mechanisms is radial diffusion, caused by the resonant interactions between energetic electrons and ULF waves in the Pc4‐5 band. An indication of this resonant interaction is believed to be the appearance of periodic flux oscillations. In this study, we report long‐lasting, drift‐periodic flux oscillations of relativistic and ultrarelativistic electrons with energies up to ∼7.7 MeV in the outer radiation belt, observed by the Van Allen Probes mission. During this March 2017 event, multi‐MeV electron flux oscillations at the electron drift frequency appeared coincidently with enhanced Pc5 ULF wave activity and lasted for over 10 h in the center of the outer belt. The amplitude of such flux oscillations is well correlated with the radial gradient of electron phase space density (PSD), with almost no oscillation observed near the PSD peak. The temporal evolution of the PSD radial profile also suggests the dominant role of radial diffusion in multi‐MeV electron dynamics during this event. By combining these observations, we conclude that these multi‐MeV electron flux oscillations are caused by the resonant interactions between electrons and broadband Pc5 ULF waves and are an indicator of the ongoing radial diffusion process during this event. They contain essential information of radial diffusion and have the potential to be further used to quantify the radial diffusion effects and aid in a better understanding of this prevailing mechanism.