Foreshock as a Source Region of Electron-scale Magnetic Holes in the Solar Wind at 1 au
Foreshock as a Source Region of Electron-scale Magnetic Holes in the Solar Wind at 1 au
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前震作为 1 au 太阳风中电子级磁洞的源区
DOI：
10.3847/1538-4357/abfd31
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发表时间：
2021
影响因子：
4.9
通讯作者：
Zhang T. L.
中科院分区：
文献类型：
--
作者：
Wang G. Q.;Volwerk M.;Xiao S. D.;Wu M. Y.;Chen Y. Q.;Zhang T. L.
电子尺度的磁空穴（ESMHs）在天体物理等离子体中具有耗散能量和输运电子的作用。它们经常在1 Au的太阳风中被观察到，但它们是否是本地产生的仍然不清楚。在这里，我们调查的ESMHs在太阳风在1 Au的观测磁层多尺度（MMS）和加速，重联，湍流和电动力学的月球与太阳的相互作用（ARTEMIS）P1航天器的基础上。MMS1和ARTEMIS P1分别观测到47次和18次ESMH事件，其中孤立的ESMH或一系列ESMH被视为ESMH事件。我们的研究结果如下：（1）MMS1观测到的ESMH事件发生率远大于ARTEMIS P1，且ARTEMIS P1位于太阳风上游，（2）离子前震中ESMH事件串在各航天器观测到的ESMH事件中所占的比例远高于未扰动太阳风中的ESMH事件串。这些观测结果表明，地面前震是1 Au处ESMH的重要源区，而一些ESMH则来自上游未扰动的太阳风。这些ESMH的产生可以用电子涡旋磁孔来解释。弄清电子涡旋的起源，有助于揭示前震中电子涡旋产生和演化的整个链条。
Electron-scale magnetic holes (ESMHs) can dissipate energy and transport electrons in astrophysical plasmas. They are often observed in the solar wind at 1 au, but whether they are locally generated remains unclear. Here we investigate the ESMHs in the solar wind at 1 au based on observations of the Magnetospheric Multiscale (MMS) and Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) P1 spacecraft. There are 47 and 18 ESMH events observed by MMS1 and ARTEMIS P1, respectively, where an isolated ESMH or a train of ESMHs is regarded as an ESMH event. Our findings are as follows: (1) the occurrence rate of the ESMH events observed by MMS1 is much larger than that by ARTEMIS P1, which is located in the upstream solar wind; and (2) the proportion of the train of ESMHs in the ESMH events observed by each spacecraft is much higher in the ion foreshock than that in the undisturbed solar wind. These observations suggest that the terrestrial foreshock is an important source region of the ESMHs at 1 au, while some ESMHs come from the upstream undisturbed solar wind. The generation of these ESMHs can be explained by the electron vortex magnetic hole. Finding out the origin of the electron vortex may help to shed light on the whole chain of their generation and evolution in the foreshock.