From Weakly to Strongly Magnetized Isotropic MHD Turbulence

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}.