From Weakly to Strongly Magnetized Isotropic MHD Turbulence

TL;DR

This study explores how isotropic MHD turbulence transitions from weak to strong magnetization, revealing different energy scaling laws and spectral behaviors depending on magnetic field strength and helicity.

Contribution

It provides new insights into the energy dissipation scaling and spectral characteristics of high Reynolds number isotropic MHD turbulence across varying magnetic field strengths.

Findings

Energy dissipation follows Kolmogorov scaling even with magnetic energy twenty times larger than kinetic.

Transition to a different scaling law occurs at high magnetic energy, indicating magnetic shear's role in energy cascade.

Magnetic energy spectra support Kolmogorov k^{-5/3} spectrum, while kinetic spectra resemble Iroshnikov-Kraichnan k^{-3/2}.

Abstract

High Reynolds number isotropic magneto-hydro-dynamic turbulence in the presence of large scale magnetic fields is investigated as a function of the magnetic field strength. For a variety of flow configurations the energy dissipation rate \epsilon, follows the Kolmogorov scaling \epsilon ~ U^3/L even when the large scale magnetic field energy is twenty times larger than the kinetic. Further increase of the magnetic energy showed a transition to the \epsilon ~ U^2 B / L scaling implying that magnetic shear becomes more efficient at this point at cascading the energy than the velocity fluctuations. Strongly helical configurations form helicity condensates that deviate from these scalings. Weak turbulence scaling was absent from the investigation. Finally, the magnetic energy spectra showed support for the Kolmogorov spectrum k^{-5/3} while kinetic energy spectra are closer to the Iroshnikov-Kraichnan spectrum k^{-3/2}.