Kolmogorov Scaling for Total Energy and Cross Helicity in Magnetohydrodynamic Turbulence

The problem of scaling in isotropic magnetohydrodynamic (MHD) turbulence has remained unresolved, with competing predictions of $k^{-5\mathrm{/}3}$ (Kolmogorov) and $k^{-3\mathrm{/}2}$ (Iroshnikov-Kraichnan) scalings. In this paper, we address this long-standing controversy using high-resolution numerical simulations on ${8192}^2$ and ${1536}^3$ grids. We show that the total energy and cross helicity spectra are closer to $k^{-5\mathrm{/}3}$ than $k^{-3\mathrm{/}2}$. The fluxes and structure functions of the total energy and cross helicity also demonstrate robust support for Kolmogorov scaling. The magnetic energy shows $k^{-5\mathrm{/}3}$ spectrum, but the kinetic energy exhibits $k^{-3\mathrm{/}2}$ spectrum; the latter spectrum is due to the energy transfers from the magnetic field to the velocity field.