Substorm convection and current system deduced from the global simulation
Substorm convection and current system deduced from the global simulation
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从全球模拟推导出的亚暴对流和洋流系统
DOI：
10.1029/2009ja014676
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
K. Hashimoto
中科院分区：
文献类型：
--
作者：
Tanaka T.;A. Nakamizo;A. Yoshikawa;S. Fujita;H. Shinagawa;H. Shimazu;T. Kikuchi;K. Hashimoto
通过分析使用最近改进的磁流体动力学模型获得的数值结果来研究亚暴机制。显示生长阶段特征后，数值解再现了亚暴爆发时观测到的特征，包括近地中性线 (NENL) 的形成、等离子体片中的向地定向流、偶极化、地球同步 D 偏转、夜侧场对准电流 (FAC) 的发展以及电离层中的电喷流。等离子体片的突然塌陷和内部磁层中高压区域的连续形成引发了这种现象。这个高压区的能量来源是 NENL 释放的磁张力。尾部扰动主要由伴随内磁层中形成的高压区的2 FAC区域传输到电离层。相关的夜侧区域 1 FAC 不连接到传统的电流楔形而是连接到尖点区域。区域1 FAC到电离层的路径从白天向夜间发展，从而与区域2 FAC从部分环流构成大环路。在大环路中，区域 1 FAC 在电离层中为区域 2 FAC 提供短路。在膨胀阶段，对流增强，松弛了开始时形成的扭曲压力分布，伴随着磁气层中等离子片的进一步发展和等离子体片的增厚，以及电离层中向西和向东电射流的增加。本模型可以解释爆炸性生长阶段和中尾血浆片在开始后变薄。
The substorm mechanism is investigated by analyzing the numerical results obtained through the use of the recently refined magnetohydrodynamic model. After showing the growth phase features, the numerical solution reproduces the observed signatures of a substorm onset, including the formation of a near‐Earth neutral line (NENL), earthward directed flow in the plasma sheet, a dipolarization, a geosynchronous D deflection, the development of the nightside field aligned currents (FACs), and electrojets in the ionosphere. The onset is triggered by a sudden collapse of the plasma sheet and a successive formation of a high‐pressure region in the inner magnetosphere. The energy source of this high‐pressure region is the magnetic tension released from the NENL. The tail disturbance is primary transmitted to the ionosphere by the region 2 FAC accompanying the high‐pressure region formed in the inner magnetosphere. The associated nightside region 1 FAC is not connected to the traditional current wedge but to the cusp region. The region 1 FAC path to the ionosphere develops from dayside to nightside, so as to construct a grand loop with the region 2 FAC from the partial ring current. In the grand loop, the region 1 FAC provides a short circuit in the ionosphere for the region 2 FAC. In the expansion phase, convection enhances to relax the distorted pressure distribution formed at the onset, accompanied by a further development of dipolarization and a thickening of the plasma sheet in the magnetosphere and increases in the westward and eastward electrojets in the ionosphere. The present model can explain the explosive growth phase and the thinning of the midtail plasma sheet just after the onset.