North-south Asymmetric Nightside Distorted Transpolar Arcs within A Framework of Deformed Magnetosphere-Ionosphere Coupling: IMF-By Dependence, Ionospheric Currents, and Magnetotail Reconnection
North-south Asymmetric Nightside Distorted Transpolar Arcs within A Framework of Deformed Magnetosphere-Ionosphere Coupling: IMF-By Dependence, Ionospheric Currents, and Magnetotail Reconnection
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DOI：
10.1002/essoar.10502674.2
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发表时间：
2020-09
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影响因子：
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通讯作者：
M. Nowada;Q. Zong;B. Hubert;Q. Shi;YongFu Wang;Jun Yang;A. Grocott;A. Degeling;A. Tian;Xuzhi Zhou;C. Yue
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文献类型：
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作者：
M. Nowada;Q. Zong;B. Hubert;Q. Shi;YongFu Wang;Jun Yang;A. Grocott;A. Degeling;A. Tian;Xuzhi Zhou;C. Yue
地球磁层永久地暴露在太阳风中的行星际磁场(IMF)中，并因此而显著变形。这种变形通常是通过空间和地面观测在32个离散位置检测到的。另一方面，地球极光是一种全球分布的现象，可用来阐明由IMF变化引起的磁层变形34，以及从变形的磁尾到高35纬度大气的等离子体供应。我们报告了利用一种被称为跨极弧36(TPA)的极光形式来诊断全球变形磁层的等离子体动力学。本文研究的9个TPA 37具有两种新鉴定的形态类型，从形状上被命名为38个“J”和“L”形TPA，并显示出在南北半球具有反对称的39个形态，这取决于基金组织的极性。40TPA相关的电离层电流剖面表明，连接磁尾和42电离层的沿41条磁力线的电流(场向电流：FAC)可能与“J”和“L”形的TPA形成有关。FAC可以是由与夜侧磁44重联相关的快速等离子体流和较慢的背景磁尾等离子体流之间的速度切变产生的。以前通过磁流体(MHD)模拟揭示的复杂的大规模TPA FAC 45结构，不能通过我们的观察来解释。然而，我们在全球背景下对TPA特征的解释47有助于将TPA用作一种诊断工具，以有效遥感响应IMF和太阳风等离子体49条件的全球变形的地球和行星磁层过程。50
30 The terrestrial magnetosphere is perpetually exposed to, and significantly deformed by the 31 Interplanetary Magnetic Field (IMF) in the solar wind. This deformation is typically detected at 32 discrete locations by spaceand ground-based observations. Earth’s aurora, on the other hand, is 33 a globally distributed phenomenon that may be used to elucidate magnetospheric deformations 34 caused by IMF variations, as well as plasma supply from the deformed magnetotail to the high35 latitude atmosphere. We report the utilization of an auroral form known as the transpolar arc 36 (TPA) to diagnose the plasma dynamics of the globally deformed magnetosphere. Nine TPAs 37 examined in this study have two types of a newly identified morphology, which are designated as 38 “J”and “L”-shaped TPAs from their shapes, and are shown to have antisymmetric 39 morphologies in the Northern and Southern Hemispheres, depending on the IMF polarity. The 40 TPA-associated ionospheric current profiles suggest that electric currents flowing along the 41 magnetic field lines (Field-Aligned Currents: FACs), connecting the magnetotail and the 42 ionosphere, may be related to the “J”and “L”-shaped TPA formations. The FACs can be 43 generated by velocity shear between fast plasma flows associated with nightside magnetic 44 reconnection and slower background magnetotail plasma flows. Complex large-scale TPA FAC 45 structures, previously unravelled by an Magnetohydrodynamic (MHD) simulation, cannot be 46 elucidated by our observations. However, our interpretation of TPA features in a global context 47 facilitates the usage of TPA as a diagnostic tool to effectively remote-sense globally deformed 48 terrestrial and planetary magnetospheric processes in response to the IMF and solar wind plasma 49 conditions. 50