Configuration of the Earth’s Magnetotail Current Sheet
Configuration of the Earth’s Magnetotail Current Sheet
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DOI：
10.1029/2020gl092153
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发表时间：
2021-03
影响因子：
5.2
通讯作者：
A. Artemyev;San Lu;M. El‐Alaoui;Yu Lin;V. Angelopoulos;Xiao‐jia Zhang;A. Runov;I. Vasko;L. Zelenyi;C. Russell
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文献类型：
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作者：
A. Artemyev;San Lu;M. El‐Alaoui;Yu Lin;V. Angelopoulos;Xiao‐jia Zhang;A. Runov;I. Vasko;L. Zelenyi;C. Russell
地球磁尾电流片的空间尺度和强度决定了磁尾的结构，这对于地球磁层中能量最强的现象之一——亚暴是至关重要的。由于缺乏等离子体电流的统计信息，磁尾电流片的理论主要基于各向同性应力平衡。这样的模型表明，薄电流片不可能很长，而且沿磁尾应该有很强的等离子体压力梯度。利用磁层多尺度和THEMIS观测和全球模拟，我们探索了磁尾电流片的真实结构。我们发现磁尾电流片比假设各向同性应力平衡的理论所期望的薄。在薄电流片中观察到的等离子体压力梯度不够强（即，电流片太长），无法平衡磁场线张力。因此，压力各向异性在亚暴开始前不稳定的薄电流片结构中是必不可少的。
The spatial scale and intensity of Earth’s magnetotail current sheet determine the magnetotail configuration, which is critical to one of the most energetically powerful phenomena in the Earth’s magnetosphere, substorms. In the absence of statistical information about plasma currents, theories of the magnetotail current sheets were mostly based on the isotropic stress balance. Such models suggest that thin current sheets cannot be long and should have strong plasma pressure gradients along the magnetotail. Using Magnetospheric Multiscale and THEMIS observations and global simulations, we explore realistic configuration of the magnetotail current sheet. We find that the magnetotail current sheet is thinner than expected from theories that assume isotropic stress balance. Observed plasma pressure gradients in thin current sheets are insufficiently strong (i.e., current sheets are too long) to balance the magnetic field line tension force. Therefore, pressure anisotropy is essential in the configuration of thin current sheets where instability precedes substorm onset.