Electron-Scale Current Sheet as the Boundary of a Linear Magnetic Hole in the Terrestrial Current Sheet Observed by the Magnetospheric Multiscale Mission
Electron-Scale Current Sheet as the Boundary of a Linear Magnetic Hole in the Terrestrial Current Sheet Observed by the Magnetospheric Multiscale Mission
复制标题
磁层多尺度任务观测到的地球电流片中以电子尺度电流片为线性磁孔边界
DOI：
10.1029/2021ja029707
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
T. L. Zhang
中科院分区：
文献类型：
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作者：
G. Q. Wang;M. Volwerk;S. D. Xiao;M. Y. Wu;Y. Q. Chen;T. L. Zhang
离子尺度和电子尺度的磁空穴广泛存在于许多空间等离子体区域，并得到了广泛的研究。然而，尺寸介于典型离子和电子尺度之间的线性磁空穴内部的带电粒子特征和电流密度尚不清楚。在这里，我们使用磁层多尺度任务的高分辨率数据报道了地面电流片中横截面尺寸为~ 2.4离子陀螺半径的LMH。我们发现，在LMH的尖锐边界处，电子速度和温度有显著变化，而离子参数没有显著变化。磁场压力的降低主要由电子热压抵消。在厚度为0.12-0.24离子陀螺半径的最外层边界上，电子漂移运动形成了强电子流，同时电场增强。这个电场可能是由于离子和电子在越过尖锐边界时的旋转变化引起的。电子流在LMH的最外侧形成一个薄的电流片，而不是分布在整个截面上。大多数被捕获的电子都被这层薄电流片包裹着。这些结果可以提高我们对尺寸介于典型离子和电子尺度之间的LMHs性质的理解。
Ion-scale and electron-scale magnetic holes widely exist in many space plasma regions, and have been extensively studied. However, characteristics of the charged particles and current densities inside the linear magnetic holes (LMHs) with a size between typical ion and electron scales are unclear. Here, we report a LMH with a cross section size of ∼2.4 ion gyroradii in the terrestrial current sheet using the high-resolution data of the Magnetospheric Multiscale Mission. We find that the electron velocity and temperature have significant variations at the sharp boundaries of this LMH, while the ion parameters have no significant change. The decrease of the magnetic field pressure is mainly balanced by the electron thermal pressure. A strong electron flow accompanied by an enhancement of the electric field is formed by electron drift motions on the outermost boundary with a thickness of 0.12–0.24 ion gyroradius. This electric field might originate from variations of the ion and electron gyrations when crossing the sharp boundary. The electron flow forms a thin current sheet on the outermost side of the LMH instead of being distributed over the entire cross section. Most of the trapped electrons are wrapped by this thin current sheet. These results could improve our understanding of the properties of LMHs with a size between typical ion and electron scales.