COMPRESSIBLE RELATIVISTIC MAGNETOHYDRODYNAMIC TURBULENCE IN MAGNETICALLY DOMINATED PLASMAS AND IMPLICATIONS FOR A STRONG-COUPLING REGIME
COMPRESSIBLE RELATIVISTIC MAGNETOHYDRODYNAMIC TURBULENCE IN MAGNETICALLY DOMINATED PLASMAS AND IMPLICATIONS FOR A STRONG-COUPLING REGIME
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DOI：
10.3847/2041-8205/831/2/l11
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发表时间：
2016-10
期刊：
影响因子：
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通讯作者：
M. Takamoto;A. Lazarian
中科院分区：
文献类型：
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作者：
M. Takamoto;A. Lazarian
在这封信中，我们使用三维数值模拟报告了坡印廷主导等离子体中相对论磁流体动力学（RMHD）湍流的可压缩模式效应。我们按照Cho和Lazarian的模态分解过程，将湍流波动分解为3种MHD模态（快、慢和Alfvén），并分别分析了它们的能谱和结构函数。我们还分析了可压缩模式与阿尔芬模式能量之比与其马赫数的关系。我们发现可压缩模式的比率不仅随着阿尔文马赫数的增加而增加，而且还随着背景磁化强度的增加而增加，这表明快速模式和阿尔文模式之间存在很强的耦合。它还意味着在坡印廷主导的等离子体中出现了新的 RMHD 湍流体系，其中快速模式和阿尔芬模式是强耦合的，并且与非相对论 MHD 体系不同，不能单独处理。这一发现将影响通过假设阿尔芬临界平衡湍流获得的粒子加速效率，并可能改变非热电子发射的光子光谱。
In this Letter, we report compressible mode effects on relativistic magnetohydrodynamic (RMHD) turbulence in Poynting-dominated plasmas using three-dimensional numerical simulations. We decomposed fluctuations in the turbulence into 3 MHD modes (fast, slow, and Alfvén) following the procedure of mode decomposition in Cho & Lazarian, and analyzed their energy spectra and structure functions separately. We also analyzed the ratio of compressible mode to Alfvén mode energy with respect to its Mach number. We found the ratio of compressible mode increases not only with the Alfvén Mach number, but also with the background magnetization, which indicates a strong coupling between the fast and Alfvén modes. It also signifies the appearance of a new regime of RMHD turbulence in Poynting-dominated plasmas where the fast and Alfvén modes are strongly coupled and, unlike the non-relativistic MHD regime, cannot be treated separately. This finding will affect particle acceleration efficiency obtained by assuming Alfvénic critical-balance turbulence and can change the resulting photon spectra emitted by non-thermal electrons.