Cascades in decaying three-dimensional electron magnetohydrodynamic turbulence
Cascades in decaying three-dimensional electron magnetohydrodynamic turbulence
复制标题
衰减三维电子磁流体动力湍流中的级联
DOI：
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发表时间：
2009
影响因子：
2.5
通讯作者：
Rainer Hollerbach
中科院分区：
文献类型：
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作者：
C. Wareing;Rainer Hollerbach
摘要通过高分辨率数值模拟研究了三维衰减电子磁流体动力学（EMHD）湍流。随着RB（控制方程中非线性时间尺度与线性时间尺度之比）的增加，所得到的能谱渐近接近k−2定律，与理论预测一致。没有发现耗散截止的证据，与非局部谱能量转移和最近的二维EMHD湍流研究一致。在以前的研究中发现的耗散截止解释为人工影响的高扩散。在另一个类似的二维EMHD湍流，相对稳定的结构被发现发展的时间，而不是在普通或MHD湍流中发现的变化。此外，在三维EMHD湍流的能量级联被发现抑制在所有方向的均匀背景场的影响下。能量转移在平行于场的方向上进一步减少，显示出尺度依赖的各向异性。最后，控制方程被发现产生一个弱的逆级联，至少部分地将磁能从小尺度转移到大尺度。
Abstract Decaying electron magnetohydrodynamic (EMHD) turbulence in three dimensions is studied via high-resolution numerical simulations. The resulting energy spectra asymptotically approach a k−2 law with increasing RB, the ratio of the nonlinear to linear time scales in the governing equation, consistent with theoretical predictions. No evidence is found of a dissipative cutoff, consistent with non-local spectral energy transfer and recent studies of 2D EMHD turbulence. Dissipative cutoffs found in previous studies are explained as artificial effects of hyperdiffusivity. In another similarity to 2D EMHD turbulence, relatively stationary structures are found to develop in time, rather than the variability found in ordinary or MHD turbulence. Further, cascades of energy in 3D EMHD turbulence are found to be suppressed in all directions under the influence of a uniform background field. Energy transfer is further reduced in the direction parallel to the field, displaying scale-dependent anisotropy. Finally, the governing equation is found to yield a weak inverse cascade, at least partially transferring magnetic energy from small to large scales.