Alexakis Alexandros
Laboratoire de Physique Statistique de l'Ecole Normale Supérieure, UMR CNRS 8550, Paris, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 Nov;84(5 Pt 2):056330. doi: 10.1103/PhysRevE.84.056330. Epub 2011 Nov 29.
The magnetohydrodynamic (MHD) equations in the presence of a guiding magnetic field are investigated by means of direct numerical simulations. The basis of the investigation consists of nine runs forced at the small scales. The results demonstrate that for a large enough uniform magnetic field the large scale flow behaves as a two-dimensional (2D) (non-MHD) fluid exhibiting an inverse cascade of energy in the direction perpendicular to the magnetic field, while the small scales behave like a three-dimensional (3D) MHD fluid cascading the energy forwards. The amplitude of the inverse cascade is sensitive to the magnetic field amplitude, the domain size, the forcing mechanism, and the forcing scale. All these dependences are demonstrated by the varying parameters of the simulations. Furthermore, in the case that the system is forced anisotropically in the small parallel scales an inverse cascade in the parallel direction is observed that is feeding the 2D modes k(//)=0.
通过直接数值模拟研究了存在引导磁场时的磁流体动力学（MHD）方程。研究的基础包括在小尺度上进行的九次模拟。结果表明，对于足够大的均匀磁场，大尺度流动表现为二维（2D）（非MHD）流体，在垂直于磁场的方向上呈现能量的反向级联，而小尺度则表现为三维（3D）MHD流体，能量向前级联。反向级联的幅度对磁场幅度、域大小、强迫机制和强迫尺度敏感。所有这些依赖性都通过模拟参数的变化得到了证明。此外，在系统在小平行尺度上各向异性强迫的情况下，观察到在平行方向上的反向级联，它为二维模式k(//)=0提供能量。
