Magnetic reconnection in high-energy-density laser-produced plasmas
Magnetic reconnection in high-energy-density laser-produced plasmas
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DOI：
10.1063/1.3694119
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发表时间：
2012-05-01
影响因子：
2.2
通讯作者：
Germaschewski, K.
中科院分区：
文献类型：
--
作者：
Fox, W.;Bhattacharjee, A.;Germaschewski, K.
近年来，在高能密度激光等离子体中进行了新的磁重联实验。单个等离子体气泡通过比尔曼电池效应自行产生环形、兆高斯尺度磁场。当多个气泡在小距离处产生时，它们会相互扩展，从而驱动该场的重新连接。据报道，实验中的重联速度比Sweet-Parker甚至Hall-MHD理论所允许的要快得多，当归一化为单个气泡自产生的名义磁场时。通过细胞内粒子模拟（包括有和没有二元碰撞算子），我们模拟了与实验相关的参数和几何形状的气泡相互作用。本文详细讨论了激光驱动实验的重联机制，并报道了模拟的定性特征。我们发现了大量的磁通堆积效应，这增强了电流片中重联的相关磁场。当考虑到这一点时，归一化重联速率更符合标准的双流体重联理论。在最大的系统尺寸下，我们还发现电流片容易破裂成等离子体。(C) 2012年美国物理研究所。[http://dx.doi.org/10.1063/1.3694119]
Recently, novel experiments on magnetic reconnection have been conducted in laser-produced plasmas in a high-energy-density regime. Individual plasma bubbles self-generate toroidal, mega-gauss-scale magnetic fields through the Biermann battery effect. When multiple bubbles are created at small separation, they expand into one another, driving reconnection of this field. Reconnection in the experiments was reported to be much faster than allowed by both Sweet-Parker, and even Hall-MHD theories, when normalized to the nominal magnetic fields self-generated by single bubbles. Through particle-in-cell simulations (both with and without a binary collision operator), we model the bubble interaction at parameters and geometry relevant to the experiments. This paper discusses in detail the reconnection regime of the laser-driven experiments and reports the qualitative features of simulations. We find substantial flux-pileup effects, which boost the relevant magnetic field for reconnection in the current sheet. When this is accounted for, the normalized reconnection rates are much more in line with standard two-fluid theory of reconnection. At the largest system sizes, we additionally find that the current sheet is prone to breakup into plasmoids. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3694119]