Statistical anisotropy of magnetohydrodynamic turbulence

Abstract

Direct numerical simulations of decaying and forced magnetohydrodynamic (MHD) turbulence without and with mean magnetic field are analyzed by higher-order two-point statistics. The turbulence exhibits statistical anisotropy with respect to the direction of the local magnetic field even in the case of global isotropy. A mean magnetic field reduces the parallel-field dynamics while in the perpendicular direction a gradual transition towards two-dimensional MHD turbulence is observed with $k^{-3/2}$ inertial-range scaling of the perpendicular energy spectrum. An intermittency model based on the log-Poisson approach, ${\zeta }_p{=p/g}^2+1\mathrm{}-{\mathrm{}(1/g)\mathrm{}}^{p/g},$ is able to describe the observed structure function scalings.