Field‐aligned current signatures in the near‐tail region: 2. Coupling between the region 1 and the region 2 systems
Field‐aligned current signatures in the near‐tail region: 2. Coupling between the region 1 and the region 2 systems
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近尾区场对准电流特征：2. 区域 1 和区域 2 系统之间的耦合
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
D. Baker
中科院分区：
文献类型：
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作者：
S. Ohtani;S. Kokubun;R. Nakamura;R. Elphic;C. Russell;D. Baker
本文从实验和理论两方面研究了近尾区亚暴相关电流系统的发展。首先，利用地面磁力仪资料和卫星磁场及高能粒子资料，对1979年3月28日的事件进行了详细的分析。在地球同步高度和在近尾区的磁场对齐的电流签名的比较表明，区域1系统的发展不仅仅是在现有系统的电流强度的增强。这一发现与所谓的电流楔模型是一致的，在该模型中，尾电流被转换成一对磁场对齐的电流与区域1极性在亚暴爆发。然而，详细的检查表明，区域2系统与区域1系统一样重要。在同步轨道的方位角磁分量的统计特性表明，在干扰期间的偏差大于预期的区域1电流的增强。这些个人和统计研究表明，2区系统往往在同步区发展，1区和2区系统之间的耦合是重要的。本文从等离子体宏观行为的角度讨论了磁层中的电流闭合。这表明，黎明和黄昏区2电流关闭磁层的曲率电流在生长阶段和磁梯度电流在膨胀阶段。区域1和区域2系统的场向电流在电离层中被Pedersen电流闭合。因此，能量以焦耳加热的形式耗散，而这种能量必须由磁层提供。因此，在磁层中闭合区域1和区域2电流的彼得森电流的对应部分必须是发电机电流。反磁电流和惯性电流是这个发电机电流的可能候选者。这些电流径向向外流动的早晨部门和向内的晚上部门与电场和等离子体压力的再分布在膨胀阶段。在发电机过程中，两个电流之间的组合可能是重要的。
The development of the substorm-associated current system in the near-tail region is examined in the light of both experiment and theory. First, the March 28, 1979, event is examined intensively by using ground magnetometer data and satellite magnetic field and energetic particle data. The comparison of field-aligned current signatures at geosynchronous altitude and in the near-tail region indicates that the development of the region 1 system is not merely the enhancement in current intensity of the pre-existing system. This finding is consistent with the so-called current wedge model, in which the tail current is converted into a pair of field-aligned currents with the region 1 polarity at substorm onsets. Detailed inspection, however, suggests that the region 2 system is as important as the region 1 system. Statistical properties of the azimuthal magnetic component at synchronous orbit indicate that the deviation during disturbed periods is larger than expected from the enhancement of the region 1 current. These individual and statistical studies suggest that the region 2 system tends to develop in the synchronous region and that the coupling between the region 1 and the region 2 systems is important. The current closure in the magnetosphere is discussed from a viewpoint of the macroscopic behavior of plasma. It is suggested that the dawnside and the duskside region 2 currents are closed in the magnetosphere by the curvature current during the growth phase and by the magnetic gradient current during the expansion phase. The field-aligned currents of the region 1 and the region 2 systems are closed in the ionosphere by the Pedersen current. Consequently, the energy is dissipated as the Joule heating and this energy must be supplied from the magnetosphere. Therefore, the counter part of the Pedersen current, which closes the region 1 and the region 2 currents in the magnetosphere, must be the dynamo current. The diamagnetic current and the inertia current are possible candidates for this dynamo current. These currents flow radially outward in the morning sector and inward in the evening sector in association with the redistributions of the electric field and the plasma pressure during the expansion phase. In the dynamo process, the combination between the two currents may be important.