arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0708.0765physics.flu-dynphysics.plasm-ph
收藏

MHD turbulence中的各向异性通量和非局域相互作用

Anisotropic fluxes and nonlocal interactions in MHD turbulence

A. Alexakis, B. Bigot, H. Politano

备注：
Submitted to PRE
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

摘要：

本文研究了在不同强度的均匀磁场$\bf B$作用下，衰减磁流体动力学（MHD）流级联中能量传递和谱相互作用的局部性和非局部性。结果是基于一个详细的分析，在中等的数值模拟流。能量传递函数，以及全球和部分通量，检查通过不同的几何波数壳。一方面，无论${\bf B}$的强度如何，两个守恒的Elsässer能量$E^+$和$E^-$的传递函数在平行于磁引导场的方向（$k_\|$ -方向）和垂直于磁引导场的方向（$k_\perp$ -方向）上都是局部的。另一方面，从通量分析，两个反向传播的Elsässer波之间的相互作用成为非局部的。事实上，随着${\bf B}$强度的增加，局部相互作用强烈降低，并且与小$k_\|$模式的相互作用在级联中占主导地位。在$k_\perp$ -方向上的大部分能流是由于在$k_\|=0$的平面中的模式，而在$k_\|$ -方向上的较弱级联是由于具有$k_\|=1$的模式。因此，较强的磁化流倾向于更接近弱湍流极限，其中三波共振相互作用占主导地位。因此，通过减少能量级联中的有效模式的数量，发生从强到弱湍流状态的过渡。

英文摘要：

We investigate the locality or nonlocality of the energy transfer and of the spectral interactions involved in the cascade for decaying magnetohydrodynamic (MHD) flows in the presence of a uniform magnetic field $\bf B$ at various intensities. The results are based on a detailed analysis of three-dimensional numerical flows at moderate Reynold numbers. The energy transfer functions, as well as the global and partial fluxes, are examined by means of different geometrical wavenumber shells. On the one hand, the transfer functions of the two conserved Elsässer energies $E^+$ and $E^-$ are found local in both the directions parallel ($k_\|$-direction) and perpendicular ($k_\perp$-direction) to the magnetic guide-field, whatever the ${\bf B}$-strength. On the other hand, from the flux analysis, the interactions between the two counterpropagating Elsässer waves become nonlocal. Indeed, as the ${\bf B}$-intensity is increased, local interactions are strongly decreased and the interactions with small $k_\|$ modes dominate the cascade. Most of the energy flux in the $k_\perp$-direction is due to modes in the plane at $k_\|=0$, while the weaker cascade in the $k_\|$-direction is due to the modes with $k_\|=1$. The stronger magnetized flows tends thus to get closer to the weak turbulence limit where the three-wave resonant interactions are dominating. Hence, the transition from the strong to the weak turbulence regime occurs by reducing the number of effective modes in the energy cascade.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

↑