Primary sources of large-scale Birkeland currents
Primary sources of large-scale Birkeland currents
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DOI：
10.1007/bf00212423
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发表时间：
1979-11
影响因子：
10.3
通讯作者：
Tetsuya Sato;T. Iijima
中科院分区：
文献类型：
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作者：
Tetsuya Sato;T. Iijima
我们回顾了磁层和电离层中伯克兰电流（场对准电流）的产生机制。将理论上预测的伯克兰电流与航天器实验观测研究的伯克兰电流进行比较，我们提出了一个驱动机制模型，该模型由太阳风-磁层相互作用统一，允许稳定粘性相互作用和非稳定磁重联并存。该模型预测如下：（1）区域1白克兰电流（位于极光白克兰电流带的极向部分，并且准永久稳定地构成白克兰电流整个系统的主要部分）将由太阳风与磁层等离子体之间的粘性相互作用产生的双细胞磁层对流核心处的涡量感应空间电荷供给， （2）区域 2 伯克兰电流（位于极光伯克兰电流带的赤道部分，表现出更多的变化和局部行为）将起源于磁层中由两细胞磁层对流和热环电流之间的耦合引起的等离子体压力不均匀区域，其中梯度 B 电流和/或曲率电流（可能是热等离子体片环电流）被迫转移到电离层，(3) 尖端白克兰电流（位于区域 1 电流的极向和邻近区域，并受到行星际磁场 (IMF) 的强烈控制）可能是惯性电流的转移，该惯性电流是在向地太阳风的速度减速区域中局部新产生的，其中磁层受到白天磁重联的侵蚀，(4) 夜间白克兰电流与西向极光的一部分相连哈朗不连续扇区的电喷射可能是由于磁尾等离子体片中等离子体密度和压力降低的局部磁重联而导致的从黄昏到黎明的尾电流的转移。
We review generation mechanisms of Birkeland currents (field-aligned currents) in the magnetosphere and the ionosphere. Comparing Birkeland currents predicted theoretically with those studied observationally by spacecraft experiments, we present a model for driving mechanism, which is unified by the solar wind-magnetosphere interaction that allows the coexistence of steady viscous interaction and unsteady magnetic reconnection. The model predicts the following: (1) the Region 1 Birkeland currents (which are located at poleward part of the auroral Birkeland-current belt, and constitute quasi-permanently and stably a primary part of the overall system of Birkeland currents) would be fed by vorticity-induced space charges at the core of two-cell magnetospheric convection arisen as a result of viscous interaction between the solar wind and the magnetospheric plasma, (2) the Region 2 Birkeland currents (which are located at equatorward part of the auroral Birkeland-current belt, and exhibit more variable and localized behavior) would orginate from regions of plasma pressure inhomogeneities in the magnetosphere caused by the coupling between two-cell magnetospheric convection and the hot ring current, where the gradient-Bcurrent and/or the curvature current (presumably the hot plasma sheet-ring current) are forced to divert to the ionosphere, (3) the Cusp Birkeland currents (which are located poleward of and adjacent to the Region 1 currents and are strongly controlled by the interplanetary magnetic field (IMF)) might be a diversion of the inertia current which is newly and locally produced in the velocity-decelerated region of earthward solar wind where the magnetosphere is eroded by dayside magnetic reconnection, (4) the nightside Birkeland currents which are connected to a part of the westward auroral electrojet in the Harang discontinuity sector might be a diversion of the dusk-to-dawn tail current resulting from localized magnetic reconnection in the magnetotail plasma sheet where plasma density and pressure are reduced.