Abstract. Thermal and subthermal electron populations in the Earth's magnetotail are usually characterized by pronounced field-aligned anisotropy that contributes to generation of strong electric currents within the magnetotail current sheet. Formation of this anisotropy requires electron field-aligned acceleration, and thus likely involves field-aligned electric fields. Such fields can be carried by various electromagnetic waves generated by fast plasma flows interacting with ambient magnetotail plasma. In this paper we consider one of the most intense observed wave emissions, kinetic Alfven waves, that often accompany fast plasma flows in the magnetotail. Using two tail seasons (2017, 2018) of MMS observations we have collected statistics of 80 fast plasma flows (or bursty bulk flows) events with distinctive enhancement of intensity of broadband electromagnetic waves (kinetic Alfven waves). We show correlation the intensity of electric fields of kinetic Alfven waves and characteristics of electron anisotropy distributions: the parallel electron anisotropy increases with magnitude of the wave parallel electric field. Also the energy range of this electron anisotropic population is well within the expected acceleration range for assumed kinetic Alfven waves. Our results indicate an important role of KAWs in production of thermal field-aligned electron population typically observed in the Earth's magnetotail.

中文翻译：

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地球磁尾中动Alfven波驱动的热电子各向异性

摘要。地球磁尾巴中的热和亚热电子种群通常以明显的场取向各向异性为特征，该各向异性有助于在磁尾电流片内产生强电流。各向异性的形成需要电子场对准的加速度，因此可能涉及场对准的电场。这样的场可以由与周围磁尾等离子体相互作用的快速等离子体流产生的各种电磁波所携带。在本文中，我们考虑了最强烈的观察到的波发射之一，即动力学阿尔夫文波，通常伴随着磁尾中快速的等离子体流。使用两个尾季（2017年，在2018年的MMS观测中，我们收集了80个快速血浆流（或突发性大流量）事件的统计数据，这些事件显着增强了宽带电磁波（运动Alfven波）的强度。我们显示出动态Alfven波的电场强度与电子各向异性分布的特征之间的相关性：平行电子各向异性随波平行电场强度的增加而增加。同样，该电子各向异性粒子的能量范围也很好地位于假定的动力学Alfven波的预期加速度范围内。我们的结果表明，KAW在通常在地球磁尾中观察到的与热场对准的电子种群的产生中具有重要作用。我们显示出动态Alfven波的电场强度与电子各向异性分布的特征之间的相关性：平行电子各向异性随波平行电场强度的增加而增加。同样，该电子各向异性粒子的能量范围也很好地位于假定的动力学Alfven波的预期加速度范围内。我们的结果表明，KAW在通常在地球磁尾中观察到的与热场对准的电子种群的产生中具有重要作用。我们显示出动态Alfven波的电场强度与电子各向异性分布的特征之间的相关性：平行电子各向异性随波平行电场强度的增加而增加。同样，该电子各向异性粒子的能量范围也很好地位于假定的动力学Alfven波的预期加速度范围内。我们的结果表明，KAW在通常在地球磁尾中观察到的与热场对准的电子种群的产生中具有重要作用。