Forward and inverse cascades in decaying two-dimensional electron magnetohydrodynamic turbulence
Forward and inverse cascades in decaying two-dimensional electron magnetohydrodynamic turbulence
复制标题
衰减二维电子磁流体动力湍流中的正向和反向级联
DOI：
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发表时间：
2009
期刊：
影响因子：
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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
通过具有正常扩散率的高分辨率数值模拟研究二维电子磁流体动力学 (EMHD) 湍流。随着 RB（控制方程中非线性与线性时间尺度的比率）的增加，所得的能谱渐近地接近 k−5/2 定律。没有发现与非局域光谱能量转移一致的耗散截止的证据。先前研究中发现的耗散截止被解释为超扩散性的人为效应。人们发现相对静止的结构会随着时间的推移而发展，而不是在普通或 MHD 湍流中发现的变化。此外，EMHD 湍流表现出与尺度相关的各向异性，在平行于均匀背景场的方向上能量传递减少，这与之前的研究一致。最后，发现控制方程产生逆级联，至少部分地将磁能从小尺度转移到大尺度。
Electron magnetohydrodynamic (EMHD) turbulence in two dimensions is studied via high-resolution numerical simulations with a normal diffusivity. The resulting energy spectra asymptotically approach a k−5/2 law with increasing RB, the ratio of the nonlinear to linear time scales in the governing equation. No evidence is found of a dissipative cutoff, consistent with nonlocal spectral energy transfer. Dissipative cutoffs found in previous studies are explained as artificial effects of hyperdiffusivity. Relatively stationary structures are found to develop in time, rather than the variability found in ordinary or MHD turbulence. Further, EMHD turbulence displays scale-dependent anisotropy with reduced energy transfer in the direction parallel to the uniform background field, consistent with previous studies. Finally, the governing equation is found to yield an inverse cascade, at least partially transferring magnetic energy from small to large scales.