Spectrum of kinetic-Alfvén-wave turbulence: intermittency or tearing mediation?
Spectrum of kinetic-Alfvén-wave turbulence: intermittency or tearing mediation?
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动力阿尔芬波湍流谱：间歇性还是撕裂中介？
DOI：
10.1093/mnras/stad2231
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发表时间：
2023
影响因子：
4.8
通讯作者：
Loureiro, Nuno F.
中科院分区：
文献类型：
--
作者：
Zhou, Muni;Liu, Zhuo;Loureiro, Nuno F.
我们利用双场等温回旋流体模型研究了弱碰撞低β等离子体中亚离子尺度湍流的频谱特性。数值结果有力地支持将湍流描述为动力学alfv<s:1>波浪波动的临界平衡kolmogorov级联，并经先前的研究修正以包括间歇性效应。测定的具有不同熔剂解冻机制的体系能谱的通用指数排除了撕裂介质在确定能谱中的作用。当它们级联到更小的尺度时，波动在垂直于强背景磁场的平面上保持各向同性，这解释了撕裂中介的缺失。对磁波动的高阶多点结构函数的计算表明，间歇结构具有准二维片状形态。这些结果有助于解释最近观测到的亚质子尺度太阳风的磁场和密度波动的频谱和结构，并与大范围天体物理系统的能量耗散建模有关。
We investigate the spectral properties of the electromagnetic fluctuations of sub-ion scale turbulence in weakly collisional, low-beta plasmas using a two-field isothermal gyrofluid model. The numerical results strongly support a description of the turbulence as a critically balanced Kolmogorov-like cascade of kinetic Alfvén wave fluctuations, as amended by previous studies to include intermittency effects. The measured universal index of the energy spectra from systems with different flux-unfreezing mechanisms excludes the role of tearing mediation in determining the spectra. The fluctuations remain isotropic in the plane perpendicular to the strong background magnetic fields as they cascade to smaller scales, which explains the absence of tearing mediation. The calculation of high-order, multipoint structure functions of magnetic fluctuations suggests that the intermittent structures have a quasi-2D, sheet-type morphology. These results are useful for explaining recent observations of the spectrum and structure of magnetic and density fluctuations in the solar wind at sub-proton scales, and are relevant for modelling the energy dissipation in a broad range of astrophysical systems.