论文标题
强磁流体动力湍流的欧拉时空相关性
The Eulerian space-time correlation of strong Magnetohydrodynamic Turbulence
论文作者
论文摘要
通过直接数值模拟MHD湍流和现象学建模的直接数值模拟，研究了强磁化等离子体中强磁流失动力学（MHD）湍流的Eulerian时空相关性。模拟得出的两个新的重要结果：1）在平衡和不平衡的湍流中以相同的速率在每个量表上的反向传播alfvénic波动； 2）与波数的波数缩放率与通过含能量的尺度的波动速度通过纯净的小尺度结构进行纯流体动力扫描一致。仿真结果的解释是在Bourouaine and Perez 2019（BP19）最新的现象学MHD模型的背景下提出的解释，仅限于强大的湍流制度。该模型预测，两次功率谱表现出一种通用的自相似行为，该行为仅取决于含能量范围内随机速度的概率分布函数。在分析和解释航天器观测值的分析和解释中，了解时空湍流相关性及其相关的通用特性的相关时间演变及其相关的通用特性，例如最近启动的帕克太阳探针（PSP）至关重要。
The Eulerian space-time correlation of strong Magnetohydrodynamic (MHD) turbulence in strongly magnetized plasmas is investigated by means of direct numerical simulations of Reduced MHD turbulence and phenomenological modeling. Two new important results follow from the simulations: 1) counter-propagating Alfvénic fluctuations at a each scale decorrelate in time at the same rate in both balanced and imbalanced turbulence; and 2) the scaling with wavenumber of the decorrelation rate is consistent with pure hydrodynamic sweeping of small-scale structures by the fluctuating velocity of the energy-containing scales. An explanation of the simulation results is proposed in the context of a recent phenomenological MHD model introduced by Bourouaine and Perez 2019 (BP19) when restricted to the strong turbulence regime. The model predicts that the two-time power spectrum exhibits an universal, self-similar behavior that is solely determined by the probability distribution function of random velocities in the energy-containing range. Understanding the scale-dependent temporal evolution of the space-time turbulence correlation as well as its associated universal properties is essential in the analysis and interpretation of spacecraft observations, such as the recently launched Parker Solar Probe (PSP).
