Collisionless reconnection: Effects of Hall current and electron pressure gradient
Collisionless reconnection: Effects of Hall current and electron pressure gradient
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DOI：
10.1029/1999ja000357
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发表时间：
2000-12
影响因子：
--
通讯作者：
Xiaogang Wang;Ashis Bhattacharjee;Zhiwei Ma
中科院分区：
文献类型：
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作者：
Xiaogang Wang;Ashis Bhattacharjee;Zhiwei Ma
在广义欧姆定律的基础上，考虑霍尔电流和标量电子压强梯度的影响，给出了二维准稳态无碰撞重联的解析处理。平衡磁场的构型是这样的，包含在z=0的中性线和恒定的引导场Bt。讨论了理想区域和重联层中波的色散关系，包括等离子体的影响。当BT=0时，重连层支持斜传播的Alfven-Well波，重连动力学受霍尔电流控制。当BT/BP0≥为1时，重联层支持动能/惯性阿尔芬波，重联动力学受电子压强梯度控制。从广义欧姆定律出发，得到了有无导向场时的非线性重联率的解析估计。Shay等人最近的一项声明。(1999)重联率是一个“普遍常量”的说法受到质疑。虽然前序重联率与破坏场线的机制(电阻率或电子惯性)无关，也与系统尺寸变大时的系统尺寸无关，但它确实取决于驱动重联的整体条件，如边界条件。通过霍尔磁流体力学模拟对分析预测进行了验证。虽然重联层的一些几何特征和重联率对电阻率的弱依赖性使人想起Petschek的经典模型，但在存在霍尔电流和电子压力梯度的情况下，调解重联的基本波和粒子动力学是本质上不同的。
An analytical treatment is given of two-dimensional, quasi-steady collisionless reconnection on the basis of the generalized Ohm's law, including the effects of the Hall current and scalar electron pressure gradient. The equilibrium magnetic field configuration is of the form , containing a neutral line at z = 0 and a constant guide field BT. The dispersion relations of the waves in the ideal region as well as the reconnection layer are discussed, including the effects of plasma beta. When BT = 0, the reconnection layer supports obliquely propagating Alfven-whistler waves, and the reconnection dynamics is controlled by the Hall current. When BT/BP0 ≥ 1, the reconnection layer supports kinetic/inertial Alfven waves, and the reconnection dynamics is controlled by the electron pressure gradient. Analytical estimates are obtained for the nonlinear reconnection rate with and without the guide field from the generalized Ohm's law. A recent claim by Shay et al. (1999) that the reconnection rate is a “universal constant” is questioned. Although the leading-order reconnection rate is independent of the mechanism that breaks field lines (resistivity or electron inertia) and the system size as the system size becomes large, it does depend on global conditions such as the boundary conditions driving reconnection. The analytical predictions are tested by means of Hall magnetohydrodynamics simulations. While some of the geometric features of the reconnection layer and the weak dependence of the reconnection rate on resistivity are reminiscent of Petschek's classical model, the underlying wave and particle dynamics mediating reconnection in the presence of the Hall current and electron pressure gradient are qualitatively different.