Numerical simulation of the combined system of nighttime region 0, region 1, and region 2 field-aligned currents
Numerical simulation of the combined system of nighttime region 0, region 1, and region 2 field-aligned currents
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夜间区域0、区域1和区域2场对准电流组合系统的数值模拟
DOI：
10.1029/2003ja010272
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发表时间：
2004
影响因子：
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通讯作者：
S. Inoue
中科院分区：
文献类型：
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作者：
Tetsuya T. Yamamoto;S. Inoue
[1]通过数值模拟，研究了在太阳风稳定、行星际磁场偏南或偏弱的条件下，夜间区域0和区域1场向电流产生的物理机制。区域0/区域1 FAC的产生附近的极光椭圆的向极边缘观察到的是密切相关的非绝热加速在尾电流片所产生的离子束的动力学。从电流片射出后，离子束沿着沿着近乎直线的场线向地球前进。在这样的时间间隔期间，离子具有微不足道的磁漂移速度。随后，它们在低海拔的镜像点被反射，并在向内对流的影响下，它们通过赤道上的磁性壳层。在那一刻，他们获得大的磁（曲率）漂移速度。因此，在稳定状态下，通量管中所有离子的平均磁漂移速度随着不变纬度的减小而增加;它在某个磁壳层处开始显着增加。在本文中，这个磁壳层被确定为在尾电流片中划分非绝热区和绝热区的界面。区域1 FAC生成的要点是该界面的变形，即界面向平均磁漂移速度方向的倾斜。区域0 FAC的产生是由于极光椭圆向极边缘附近的通电离子的异常交叉场扩散。在模拟中从区域0/区域1 FAC产生的磁场扰动的纵向轮廓与区域0/区域1薄电流片系统的观测到的磁场特征非常相似。
[1] A numerical simulation is performed to identify the physical mechanisms for the generation of the nighttime region 0 and region 1 field-aligned currents (FACs) in conditions of a steady solar wind with a southward or weak interplanetary magnetic field. The generation of region 0/region 1 FACs observed near the poleward edge of the auroral oval is closely associated with the dynamics of ion beams produced by nonadiabatic acceleration in the tail current sheet. After ejection from the current sheet, ion beams advance toward the Earth along the nearly straight field lines. During such a time interval, the ions have insignificant magnetic drift velocities. Subsequently, they are reflected at low-altitude mirror points, and under the influence of inward convection they pass the equator on magnetic shells that are further in. At that moment they attain large magnetic (curvature) drift velocities. Accordingly, in a steady state, the magnetic drift speed averaged over all the ions in a flux tube increases with decreasing invariant latitude; it starts to increase significantly at a certain magnetic shell. In the present paper this magnetic shell is identified with the interface demarcating the nonadiabatic and adiabatic regions in the tail current sheet. An essential point for the region 1 FAC generation is distortion of this interface, namely inclination of the interface to the direction of the average magnetic drift velocity. The generation of region 0 FACs is due to anomalous cross-field diffusion of energized ions near the poleward edge of the auroral oval. Latitudinal profiles of magnetic field perturbations arising from region 0/region 1 FACs in the simulation are remarkably similar to observed magnetic field signatures of the region 0/region 1 thin-current-sheet systems.
T.Yamamoto：“磁层中热等离子体环面动力学和极化的数值研究：成对区域 1 和区域 2 场对准电流的产生原因”J.Geomag。
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T.Yamamoto：“在配对的区域 1 和区域 2 场对准电流系统中极光欧米茄带的形成”J.Geophys.Res.（正在出版）。
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