On the Role of Whistler‐Mode Waves in Electron Interaction With Dipolarizing Flux Bundles
On the Role of Whistler‐Mode Waves in Electron Interaction With Dipolarizing Flux Bundles
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DOI：
10.1029/2022ja030265
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
A. Artemyev;A. Neishtadt;V. Angelopoulos
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文献类型：
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作者：
A. Artemyev;A. Neishtadt;V. Angelopoulos
磁尾是地球内磁层高能电子的主要来源。电子在流爆发（等离子体快速向地球运动）期间在双极化通量束（磁场的同时增加和双极化）内被加热。电子加热在双极化通量束附近或之内被证明为高能电子通量（10-100 keV）的快速增加;它通常被称为注入。注入电子分布的各向异性通常垂直于磁场，产生哨声模式波，也通常在这种双极化通量束周围观察到。测试粒子模拟再现了注入和电子绝热动力学的几个特征。然而，电子分布上的波的反馈还没有被纳入这样的模拟。这是因为到目前为止，还不清楚是否有必要结合这种反馈来解释电子俯仰角和能量分布从它们的起源，中尾区域的重连喷出物到它们的最终目的地以及内磁层中的电子注入点的演变。使用一个分析模型，我们证明了波反馈确实是重要的电子分布的演变。结合正则引导中心理论和映射技术，我们模拟了电子绝热加热和哨声模波围绕双极化通量束的散射。与航天器观测的比较，使我们能够验证所提出的方法的有效性。具体来说，我们证明了电子与哨声模式波的共振相互作用确实可以显着改变注入位点处高能电子的俯仰角分布，因此为了解释观察结果，结合起来至关重要。我们讨论了这种共振相互作用的注入物理和磁层电离层耦合的重要性。
The magnetotail is the main source of energetic electrons for Earth’s inner magnetosphere. Electrons are adiabatically heated during flow bursts (rapid earthward motion of the plasma) within dipolarizing flux bundles (concurrent increases and dipolarizations of the magnetic field). The electron heating is evidenced near or within dipolarizing flux bundles as rapid increases in the energetic electron flux (10–100 keV); it is often referred to as injection. The anisotropy in the injected electron distributions, which is often perpendicular to the magnetic field, generates whistler‐mode waves, also commonly observed around such dipolarizing flux bundles. Test‐particle simulations reproduce several features of injections and electron adiabatic dynamics. However, the feedback of the waves on the electron distributions has been not incorporated into such simulations. This is because it has been unclear, thus far, whether incorporating such feedback is necessary to explain the evolution of the electron pitch‐angle and energy distributions from their origin, reconnection ejecta in the mid‐tail region, to their final destination, and the electron injection sites in the inner magnetosphere. Using an analytical model we demonstrate that wave feedback is indeed important for the evolution of electron distributions. Combining canonical guiding center theory and the mapping technique we model electron adiabatic heating and scattering by whistler‐mode waves around a dipolarizing flux bundle. Comparison with spacecraft observations allows us to validate the efficacy of the proposed methodology. Specifically, we demonstrate that electron resonant interactions with whistler‐mode waves can indeed change markedly the pitch‐angle distribution of energetic electrons at the injection site and are thus critical to incorporate in order to explain the observations. We discuss the importance of such resonant interactions for injection physics and for magnetosphere‐ionosphere coupling.