A theory for generation of the paired region 1 and region 2 field‐aligned currents
A theory for generation of the paired region 1 and region 2 field‐aligned currents
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生成配对区域 1 和区域 2 场对准电流的理论
DOI：
10.1029/96ja01717
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发表时间：
1996
影响因子：
--
通讯作者：
C. Meng
中科院分区：
文献类型：
--
作者：
Takashi Yamamoto;S. Inoue;N. Nishitani;M. Ozaki;C. Meng
本文提出了一个新的理论模型，在行星际磁场向南的条件下，产生一对1区和2区场向电流。卫星观测的基础上，它是假设的热（101 keV）等离子体粒子分布在一个磁壳连接到两个椭圆形的扩散极光的北方和南极电离层。包含在这个磁壳层中的热等离子体群体具有几个纬度的宽度，被称为热等离子体环（HPT）。有人提出，区域1/区域2的FACs可以产生作为由于太阳风对流的HPT的自然变形的结果。当行星际磁场有向南分量时，即，当IMF Bz为负值时，太阳风通过开放磁力线时，在极冠上空产生电场对流模式，这种模式被模拟为双涡胞，极冠中心有反向阳流。因此，由太阳风驱动的对流被称为太阳风对流。如果不是E × B对流，HPT的形状将使HPT颗粒包含在“磁漂移壳”中，该“磁漂移壳”与平均总磁漂移速度相切。在太阳风对流的存在下，磁漂移壳层将使HPT的位形发生变形。由于HPT的畸变，HPT中的压力梯度获得了平行于磁漂移的分量。因此，由于HPT电子和质子的磁漂移方向相反，HPT可以被极化：HPT的高纬度和低纬度侧在eveningside分别是负的和正的，而极性在morningside是相反的。由于HPT的极化而产生的大规模场向电流的模式与区域1和区域2 FACs的观察结果一致。此外，假设太阳风在与开放场线的相互作用中充当电压发生器，作为成对的区域1和区域2 FAC的长期特性，我们可以获得FAC强度与电离层电导率之间的关系：区域1和区域2的强度都随着Pedersen电导率线性增加，而区域2FAC的比例常数小于区域1FAC的比例常数。我们预测的地磁平静条件的关系与Fujii和Iijima [1987]根据Magsat卫星观测得到的电流强度和Pedersen电导率之间的回归线在数量上是一致的。
We present a new theoretical model for generation of a pair of region 1 and region 2 field-aligned currents (FACs) under the condition of a southward interplanetary magnetic field. On the basis of the satellite observations it is assumed that the hot (≳1 keV) plasma particles are distributed in a magnetic shell connected to two ovals of diffuse auroras on the northern and southern polar ionospheres. The hot plasma population contained in this magnetic shell having several degrees of latitude in width is called the hot plasma torus (HPT). It is proposed that the region 1/region 2 FACs can be generated as a result of natural distortion of the HPT due to the solar wind convection. When the interplanetary magnetic field has a southward component, i.e., the IMF Bz is negative, the solar wind flow across open geomagnetic field lines gives rise to electric field convection patterns over the polar caps, which are modeled as twin vortex cells with antisunward flows in the center of the polar caps. The convection thus driven by the solar wind is referred to as the solar wind convection. If it were not for an E × B convection flow, the HPT would be shaped such that the HPT particles are contained in the “magnetic drift shells,” which are tangent to the averaged total magnetic drift velocity. In the presence of the solar wind convection, the configuration of the HPT will be deformed from the magnetic drift shells. Because of the distortion of the HPT, the pressure gradient in the HPT gains a component parallel to the magnetic drift. Therefore the HPT can be polarized because of oppositely directed magnetic drifts of the HPT electrons and protons: the high-latitude and low-latitude sides of the HPT on the eveningside are negative and positive, respectively, and the polarity is reversed on the morningside. The resulting pattern of large-scale field-aligned currents due to the polarization of the HPT is consistent with the observations of region 1 and region 2 FACs. Moreover, provided that the solar wind acts as a voltage generator in the interaction with the open field lines, as a long-term characteristic of the paired region 1 and region 2 FACs we can obtain the relationship between the FAC intensity and the ionospheric conductivity: both the region 1 and region 2 intensities increase linearly with the Pedersen conductivity, while the proportionality constant for the region 2 FAC is smaller than that for the region 1 FAC. Our predicted relation for geomagnetic quiet conditions quantitatively agrees with the regression lines between the current intensities and the Pedersen conductivities obtained on the basis of Magsat satellite observations by Fujii and Iijima [1987].
影响因子：
10.3
作者：
Tetsuya Sato;T. Iijima
通讯作者：
Tetsuya Sato;T. Iijima