Small-scale anisotropic intermittency in magnetohydrodynamic turbulence at low magnetic Reynolds numbers

Abstract

Small-scale anisotropic intermittency is examined in three-dimensional incompressible magnetohydrodynamic turbulence subjected to a uniformly imposed magnetic field. Orthonormal wavelet analyses are applied to direct numerical simulation data at moderate Reynolds number and for different interaction parameters. The magnetic Reynolds number is sufficiently low such that the quasistatic approximation can be applied. Scale-dependent statistical measures are introduced to quantify anisotropy in terms of the flow components, either parallel or perpendicular to the imposed magnetic field, and in terms of the different directions. Moreover, the flow intermittency is shown to increase with increasing values of the interaction parameter, which is reflected in strongly growing flatness values when the scale decreases. The scale-dependent anisotropy of energy is found to be independent of scale for all considered values of the interaction parameter. The strength of the imposed magnetic field does amplify the anisotropy of the flow.

Wavelet transforms and their applications to MHD and plasma turbulence: a review

“… and , as shown in Okamoto et al. (2014). Combining (2.17) and (2.18) results in which yields a scale-dependent measure of component-wise anisotropic intermittency.…”

“…In the following, we give a summary of statistical diagnostics based on orthogonal wavelet analysis, here applied to a generic vector field following the lines of Okamoto et al. (2014). Decomposing a vector field into orthogonal wavelets, scale-dependent distributions of turbulent flows can be measured, including different directions and also different flow components.…”

“…QS-3D-MHD: Modulus of vorticity for quasistatic 3D MHD at R λ = 235, with N = 0, (left) and N = 2 (right) computed by DNS, from[35].…”

“…QS-3D-MHD: Component-wise anisotropy measure c E (k j ) (left) and directional anisotropy measure in the longitudinal direction d L E (k j ). From[35].…”

Coherent Structure Formation through nonlinear interactions in 2D Magnetohydrodynamic Turbulence

“…In order to identify the intermittent pattern formed at small scale in turbulent flow, we used a wavelet decomposition analysis, through an Haar wavelet base in two dimensions 26 , 32 – 38 . In accordance with the wavelet decomposition, for , we define the scale (see section Methods).…”