Electron Acceleration by Magnetosheath Jet‐Driven Bow Waves
Electron Acceleration by Magnetosheath Jet‐Driven Bow Waves
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DOI：
10.1029/2019ja027709
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发表时间：
2020-02
期刊：
影响因子：
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通讯作者：
T. Liu;H. Hietala;V. Angelopoulos;R. Vainio;Y. Omelchenko
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文献类型：
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作者：
T. Liu;H. Hietala;V. Angelopoulos;R. Vainio;Y. Omelchenko
磁鞘喷流是一种动压增强的局部快速流动。当它们以超磁声压缩周围的磁鞘等离子体时，在它们前面会形成弓形波或激波。最近观察到这样的弓形波可以加速离子，可能还有电子。离子加速过程之前已经分析过，但电子加速过程在很大程度上仍未探索。在这里，我们使用事件的时间历史和亚暴期间的宏观尺度从三个事件的多点观测，以确定磁鞘喷流驱动的弓形波是否以及如何加速电子。我们表明，当超热电子在周围的磁鞘对流向弓波，一些电子的冲击漂移加速和反射向周围的磁鞘和其他继续移动的弓波的下游，导致双向运动。我们的研究表明，磁鞘喷流驱动的弓形波可以导致额外的超热电子在磁鞘中。这意味着磁鞘喷流可以提高行星弓激波或其他类似天体物理环境中电子加速的效率。
Magnetosheath jets are localized fast flows with enhanced dynamic pressure. When they supermagnetosonically compress the ambient magnetosheath plasma, a bow wave or shock can form ahead of them. Such a bow wave was recently observed to accelerate ions and possibly electrons. The ion acceleration process was previously analyzed, but the electron acceleration process remains largely unexplored. Here we use multipoint observations by Time History of Events and Macroscale during Substorms from three events to determine whether and how magnetosheath jet‐driven bow waves can accelerate electrons. We show that when suprathermal electrons in the ambient magnetosheath convect toward a bow wave, some electrons are shock‐drift accelerated and reflected toward the ambient magnetosheath and others continue moving downstream of the bow wave resulting in bidirectional motion. Our study indicates that magnetosheath jet‐driven bow waves can result in additional energization of suprathermal electrons in the magnetosheath. It implies that magnetosheath jets can increase the efficiency of electron acceleration at planetary bow shocks or other similar astrophysical environments.