Effect of Anomalous Cross-Field Diffusion on the Field-Aligned Current Generation
Effect of Anomalous Cross-Field Diffusion on the Field-Aligned Current Generation
复制标题
反常交叉场扩散对场对准电流产生的影响
DOI：
10.5636/jgg.49.923
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
C. Meng
中科院分区：
文献类型：
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作者：
Takashi Yamamoto;S. Inoue;C. Meng
首先，根据极光磁层中宽带静电噪声和阿尔芬波噪声的卫星观测，在准线性理论框架内，至少在扰动周期内，通量管上平均的质子(反常交叉场)扩散系数可能达到玻姆率的很大一部分。其次，作为最近提出的一种模型的推广，即在通常具有双涡旋的对流的影响下(当行星际磁场向南时)，磁层中的热等离子体环(HPT)可以产生一对区域1和区域2的场向电流(FAC)，我们研究了HPT极化引起的反常跨场扩散对大尺度FACS的可能影响。在磁层中，热(≥1keV)等离子体粒子主要分布在一个磁性壳层中，该壳层连接着南北极电离层上的两个椭圆形扩散极光。这种热等离子体群被称为热等离子体环(HPT)。数值计算特别表明，这种影响对FAC模式的主要修改是在午夜扇区出现了三重FAC结构(即夹在两个向下的FAC区之间的向上FAC区)，至少在亚暴期间可以从卫星观测中识别出这种结构。作为形成这种三重FAC结构的直接结果，在电势图中出现了Harang不连续。因此，Harang不连续的形成可以理解为磁漂移和反常跨场扩散共同作用下HPT极化的结果。
First, on the basis of the satellite observations of the broadband electrostatic noise and the Alfven wave noise in the auroral magnetosphere, within a frame of the quasi-linear theory we show that the proton (anomalous cross-field) diffusion coefficient averaged over the flux tube is likely to reach a significant fraction of the Bohm rate at least in the disturbed periods. Second, as an extension of recently proposed model that a pair of the region 1 and region 2 field-aligned currents (FACs) can be generated as a result of "natural distortion" of the hot plasma torus (HPT) in the magnetosphere under the influence of the usually prevailing convection with twin vortex cells (when the interplanetary magnetic field (IMF) is southward), we study the possible effect of the anomalous cross-field diffusion on the large-scale FACs resulting from the HPT polarization. In the magnetosphere, the hot (≥ 1 keV) plasma particles are primarily distributed in a magnetic shell which is connected to two ovals of diffuse auroras on the northern and southern polar ionospheres. Such hot plasma population is called the hot plasma torus (HPT). The numerical calculations specifically show that primary modification of the FAC pattern by this effect is the appearance of the triple FAC structure (i.e., upward FAC zone sandwiched between two downward FAC zones) in the midnight sector, which can be identified from the satellite observations at least during substorm periods. As a direct consequence of formation of such a triple FAC structure, the Harang discontinuity appears in the electric potential pattern. Thus the formation of the Harang discontinuity can be understood as a result of the HPT polarization by both effects of magnetic drift and anomalous cross-field diffusion.
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。
DOI：
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发表时间：
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期刊：
影响因子：
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通讯作者：
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