As a Matter of Tension: Kinetic Energy Spectra in MHD Turbulence
As a Matter of Tension: Kinetic Energy Spectra in MHD Turbulence
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DOI：
10.3847/1538-4357/abdd22
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发表时间：
2021-03-01
影响因子：
4.9
通讯作者：
Beckwith, Kris
中科院分区：
文献类型：
--
作者：
Grete, Philipp;O'Shea, Brian W.;Beckwith, Kris
虽然磁化湍流在许多天体物理和地球系统中普遍存在，但我们对这种现象的最简单物理描述，即理想磁流体动力学（MHD）湍流的理解仍然很不完整。在这项工作中，我们强调现有的理论和唯象描述的MHD湍流，重点是联合（动能和磁）的能量通量和频谱的缺点，通过证明，分别处理这些量，使基本的洞察力MHD湍流的动力学。这是通过对亚音速、超Alfvenic MHD湍流的隐式大涡模拟中随时间推移的尺度能量传递进行分析来实现的。我们的关键发现是，动能谱在静止状态下形成约k（-4/3）的标度，因为磁张力介导了大规模动能到磁能的转换，并显着抑制了动能级联。这促使重新评估现有的MHD湍流理论的能量通量的一个更有区别的建模。
While magnetized turbulence is ubiquitous in many astrophysical and terrestrial systems, our understanding of even the simplest physical description of this phenomena, ideal magnetohydrodynamic (MHD) turbulence, remains substantially incomplete. In this work, we highlight the shortcomings of existing theoretical and phenomenological descriptions of MHD turbulence that focus on the joint (kinetic and magnetic) energy fluxes and spectra by demonstrating that treating these quantities separately enables fundamental insights into the dynamics of MHD turbulence. This is accomplished through the analysis of the scale-wise energy transfer over time within an implicit large eddy simulation of subsonic, super-Alfvenic MHD turbulence. Our key finding is that the kinetic energy spectrum develops a scaling of approximately k(-4/3) in the stationary regime as magnetic tension mediates large-scale kinetic to magnetic energy conversion and significantly suppresses the kinetic energy cascade. This motivates a reevaluation of existing MHD turbulence theories with respect to a more differentiated modeling of the energy fluxes.