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arXiv 1802.07549astro-ph.HEastro-ph.SRphysics.plasm-ph
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三维相对论电流片的演化与自生Turbulence的发展

Evolution of 3-dimensional Relativistic Current Sheets and Development of Self-Generated Turbulence

Makoto Takamoto

摘要:

本文首次研究了坡印廷主导等离子体中三维相对论性电流片的时间演化。在过去的几十年里,人们对二维空间中电流片的演化进行了大量的研究,并得出结论:足够长的电流片总是演化成所谓的“等离子体团链”,它提供了与其电阻率无关的快速重联速率。然而,人们怀疑等离子体团链只能在二维近似的情况下存在,并且在三维空间中会表现出向湍流的转变。采用电阻性相对论磁流体力学近似对相对论电流片进行了三维数值模拟。结果表明,三维电流片演化为湍流,而不是等离子体团链。由此产生的重连率是$0.004$,它比类质体链的重连率小得多。从磁场到湍流动能的能量转换仅为0.01%,比典型的非相对论情况小得多。利用能量原理,我们还表明,等离子体团总是不稳定的位移在相反的方向上,其加速度,可能是ESTA型不稳定性,这总是导致种子的湍流背后的等离子体团。最后,讨论了温度沿片的分布,发现片的活性比等离子体团链的活性小。我们的发现可以应用于许多高能天体物理现象,并可以提供一个基本的模型,一般电流片在坡印廷占主导地位的等离子体。

英文摘要:

In this paper, the temporal evolution of 3-dimensional relativistic current sheets in Poynting-dominated plasma is studied for the first time. Over the past few decades, a lot of efforts have been conducted on studying the evolution of current sheets in 2-dimensional space, and concluded that sufficiently long current sheets always evolves into the so-called "plasmoid-chain", which provides fast reconnection rate independent of its resistivity. However, it is suspected that plasmoid-chain can exist only in the case of 2-dimensional approximation, and would show transition to turbulence in 3-dimensional space. We performed 3-dimensional numerical simulation of relativistic current sheet using resistive relativistic magnetohydrodynamic approximation. The results showed that the 3-dimensional current sheet evolve not into plasmoid-chain but turbulence. The resulting reconnection rate is $0.004$ which is much smaller than that of plasmoid-chain. The energy conversion from magnetic field to kinetic energy of turbulence is just 0.01\% which is much smaller than typical non-relativistic cases. Using the energy principle, we also showed that the plasmoid is always unstable for a displacement in opposite direction to its acceleration, probably interchange-type instability, and this always results in seeds of turbulence behind the plasmoids. Finally, the temperature distribution along the sheet is discussed, and it is found that the sheet is less active than plasmoid-chain. Our finding can be applied for many high energy astrophysical phenomena, and can provide a basic model of the general current sheet in Poynting-dominated plasma.

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