论文标题

局部级联和不可压缩的霍尔磁流失动力动力湍流:粗粒剂方法

Local cascade and dissipation in incompressible Hall magnetohydrodynamic turbulence: the Coarse-Graining approach

论文作者

Manzini, Davide, Sahraoui, Fouad, Califano, Francesco, Ferrand, Renaud

论文摘要

我们得出了不可压缩的Hall磁性水力动力学(HMHD)湍流的粗粒(CG)方程,以研究{\ it local(In space)}能量级联速率作为滤波量表$ \ ell $的函数。首先,将CG方程平均以获得平均级联速率的分析表达。它应用于(弱压缩)HMHD的3个维(3D)模拟显示级联率与模拟中平均耗散率的值以及基于“三阶”定律的经典估计值一致。此外,我们开发了CG的各向异性版本,使我们能够相对于平均磁场研究沿不同方向的级联速率的大小。它在具有中等背景磁场的数值数据上的实现表明,沿磁场的级联反应较弱,而在没有背景场的情况下恢复了各向同性级联反应。当考虑{\ IT局部空间}能量传递时,CG方法的强度进一步揭示,当在给定位置$ \ bm {x} $上匹配时,在(Quasi-)局部消散上进行本地平均。讨论了利用这种新模型来研究航天器数据中局部耗散的前景。

We derive the coarse-graining (CG) equations of incompressible Hall Magnetohydrodynamics (HMHD) turbulence to investigate the {\it local (in space)} energy cascade rate as a function of the filtering scale $\ell$. First, the CG equations are space averaged to obtain the analytical expression of the mean cascade rate. Its application to 3 dimensional (3D) simulations of (weakly compressible) HMHD shows a cascade rate consistent with the value of the mean dissipation rate in the simulations and with the classical estimates based on the "third-order" law. Furthermore, we developed an anisotropic version of CG that allows us to study the magnitude of the cascade rate along different directions with respect to the mean magnetic field. Its implementation on the numerical data with moderate background magnetic field shows a weaker cascade along the magnetic field than in the perpendicular plane, while an isotropic cascade is recovered in the absence of a background field. The strength of the CG approach is further revealed when considering the {\it local-in-space} energy transfer, which is shown theoretically and numerically to match at a given position $\bm{x}$, when locally averaged over a neighboring region, the (quasi-)local dissipation. Prospects of exploiting this new model to investigate local dissipation in spacecraft data are discussed.

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