Anisotropy in Quasi-Static Magnetohydrodynamic Turbulence

TL;DR

This review discusses the characteristics of quasi-static magnetohydrodynamic turbulence, highlighting its anisotropic energy spectrum, flow structure, and energy transfer mechanisms influenced by Joule dissipation and magnetic fields.

Contribution

It provides a comprehensive summary of the current understanding of anisotropy and energy transfer in quasi-static MHD turbulence, emphasizing spectral steepening and flow dimensionality.

Findings

Energy spectrum is steeper than Kolmogorov's $k^{-5/3}$ due to Joule dissipation.

Flow exhibits quasi two-dimensional behavior with distinct velocity components.

Pressure mediates energy transfer between perpendicular and parallel velocity components.

Abstract

In this review we summarise the current status of the quasi-static magnetohydrodynamic turbulence. The energy spectrum is steeper than Kolmogorov's $k^{-5/3}$ spectrum due to the decrease of the kinetic energy flux with wavenumber $k$ as a result of Joule dissipation. The spectral index decreases with the increase of interaction parameter. The flow is quasi two-dimensional with strong ${\bf U}_\perp$ at small $k$ and weak $U_\parallel$ at large $k$, where ${\bf U}_\perp$ and $U_\parallel$ are the perpendicular and parallel components of velocity relative to the external magnetic field. For small $k$, the energy flux of ${\bf U}_\perp$ is negative, but for large $k$, the energy flux of $U_\parallel$ is positive. Pressure mediates the energy transfer from ${\bf U}_\perp$ to $U_\parallel$.