论文标题
确定MHD湍流级联速率的策略：各向异性，各向异性和航天器采样
Strategies for determining the cascade rate in MHD turbulence: isotropy, anisotropy, and spacecraft sampling
论文作者
论文摘要
评估级联费率的``确切''定律，追溯到Kolmogorov``4/5''定律，已扩展到许多感兴趣的系统，包括磁性水力动力学（MHD），以及磁磁体和普通流体类型的可压缩流。可以理解，实现可能受到可用数据数量和缺乏湍流对称性的限制。通过以增量形式检查von Karman-Howarth方程，对这种``三阶''（或Yaglom）关系的准确性和可行性的评估最有效，这是一个框架，该框架从中得出了三阶定律作为渐近近似近似。使用这种方法，我们详细介绍了不可压缩的MHD的三阶定律的上下文。最简单的版本依赖于各向同性的假设和定义明确的惯性范围的存在，而相关的过程将相同的想法推广到任意旋转对称性。使用模拟的结果研究了基于几种抽样和拟合策略的这些定律的正确和准确值的条件。我们解决的问题与一个或多个航天器对太阳风湍流的采样特别相关。
``Exact'' laws for evaluating cascade rates, tracing back to the Kolmogorov ``4/5'' law, have been extended to many systems of interest including magnetohydrodynamics (MHD), and compressible flows of the magnetofluid and ordinary fluid types. It is understood that implementations may be limited by the quantity of available data and by the lack of turbulence symmetry. Assessment of the accuracy and feasibility of such ``third-order'' (or Yaglom) relations is most effectively accomplished by examining the von Karman-Howarth equation in increment form, a framework from which the third-order laws are derived as asymptotic approximations. Using this approach, we examine the context of third-order laws for incompressible MHD in some detail. The simplest versions rely on the assumption of isotropy and the presence of a well-defined inertial range, while related procedures generalize the same idea to arbitrary rotational symmetries. Conditions for obtaining correct and accurate values of the dissipation rate from these laws based on several sampling and fitting strategies are investigated using results from simulations. The questions we address are of particular relevance to sampling of solar wind turbulence by one or more spacecraft.
