Reconnection in a weakly stochastic field
Reconnection in a weakly stochastic field
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DOI：
10.1086/307233
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发表时间：
1999-06-01
影响因子：
4.9
通讯作者：
Vishniac, ET
中科院分区：
文献类型：
--
作者：
Lazarian, A;Vishniac, ET
我们研究了弱的，小尺度的磁场结构对强磁化等离子体中的重联率的影响。这通过减少重联hows的横向尺度和允许许多独立的通量重联事件同时发生来影响重联的速率。在只考虑第一种效应的情况下，利用Goldreich & Sridhar的磁化等离子体强湍流模型，我们得到了近似于（VARL-3/16 M ~ 3/4）的重联速度下限，其中V-A为阿尔芬速度，R-L为伦德奎斯特数，M为湍流的大尺度磁马赫数。我们通过调用这两个效应推导出类似于VAM 2的上限。我们认为，一般的重联在湍流：等离子体通常会发生在接近这个上限。直接进入电子加热的磁能比例为（RL-2/5 M 8/5），电流片的厚度比例为RL-3/5 M-2/5。很大一部分磁能进入高频阿尔芬波。在重连层的同一侧上的相邻场线之间的角度在当前片厚度的尺度上类似于（RL-1/5 M6/5）。我们声称，这些结论的定性意义，即重联是快速的，即使电流片是狭窄的，几乎是独立的本地物理重联和湍流级联的性质。因此，银河系和太阳系的发电机一般都很快，即，不依赖于等离子体电阻率。
We examine the effect of weak, small-scale magnetic field structure on the rate of reconnection in a strongly magnetized plasma. This affects the rate of reconnection by reducing the transverse scale for reconnection hows and by allowing many independent flux reconnection events to occur simultaneously. Allowing only for the first effect and using Goldreich & Sridhar's model of strong turbulence in a magnetized plasma with negligible intermittency, we find a lower limit for the reconnection speed similar to (VARL-3/16M3/4),where V-A is the Alfven speed, R-L is the Lundquist number, and M is the large-scale magnetic Mach number of the turbulence. We derive an upper Limit of similar to VAM2 by invoking both effects. We argue that generic reconnection in turbulent: plasmas will normally occur at close to this upper limit. The fraction of magnetic energy that goes directly into electron heating scales as (RL-2/5M8/5), and the thickness of the current sheet scales as RL-3/5M-2/5. A significant fraction of the magnetic energy goes into high-frequency Alfven waves. The angle between adjacent field lines on the same side of the reconnection layer is similar to (RL-1/5M6/5) on the scale of the current sheet thickness. We claim that the qualitative sense of these conclusions, that reconnection is fast even though current sheets are narrow, is almost independent of the local physics of reconnection and the nature of the turbulent cascade. As the consequence of this the Galactic and solar dynamos are generically fast, i.e., do not depend on the plasma resistivity.