Superthin current sheets supported by anisotropic electrons
Superthin current sheets supported by anisotropic electrons
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DOI：
10.1063/5.0018063
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发表时间：
2020-08
影响因子：
2.2
通讯作者：
S. Kamaletdinov;E. Yushkov;A. Artemyev;Alexander Lukin;I. Vasko
中科院分区：
文献类型：
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作者：
S. Kamaletdinov;E. Yushkov;A. Artemyev;Alexander Lukin;I. Vasko
具有强横向（交叉场）电流的电流片通常在行星磁层中观察到，并作为磁场重联的天然能源。作为研究最多的电流片，地球磁尾电流片形成于高β等离子体中，热离子主要贡献于抗磁电流。然而，航天器的观测表明，超薄的电子主导电流片可以嵌入地球的磁尾电流片中。在本文中，我们发展了一个模型，这种超薄电流片与各向异性电子产生的强电流。我们还比较了模型与航天器的观测，这表明合理的协议的空间分布和电流密度的大小。超薄电流片的空间尺度（厚度）由赤道磁场分量控制，而电流密度大小由赤道处的电子消防软管参数控制。尽管超薄电流片中的电流密度峰值可以显著超过背景（嵌入）电流密度，但超薄电流片边界处的磁场幅值不超过总磁场幅值的10%。这些超薄电流片是子离子（或甚至电子尺度）结构，其不足以大/强到扰动离子动力学。我们讨论了该模型在超薄电子主导电流片等离子体不稳定性分析中的应用。
Current sheets with strong transverse (cross field) currents are commonly observed in planetary magnetospheres and serve as a natural energy source for magnetic reconnection. As the most investigated current sheet, the current sheet in the Earth's magnetotail forms in a high-β plasma, with hot ions dominantly contributing to the diamagnetic currents. Spacecraft observations have shown, however, that a superthin electron dominated current sheet can be embedded in the Earth's magnetotail current sheet. In this paper, we develop a model of such superthin current sheets with strong currents produced by anisotropic electrons. We also compare the model with spacecraft observations, which shows reasonable agreement in spatial profiles and magnitudes of the current density. The spatial scale (thickness) of the superthin current sheet is controlled by the equatorial magnetic field component, whereas the current density magnitude is controlled by the electron fire-hose parameter at the equator. Although the current density peak within the superthin current sheet can significantly exceed the background (embedding) current density, the magnetic field magnitude at the superthin current sheet boundary does not exceed 10% of the total magnetic field magnitude. These superthin current sheets are sub-ion (or even electron-scale) structures, which are not sufficiently large/intense to perturb ion dynamics. We discuss applications of the proposed model for the analysis of plasma instabilities in superthin electron-dominated current sheets.