The residual energy in freely decaying magnetohydrodynamic turbulence
Résumé
Within the framework of the eddy-damped quasi-normal Markovian approximation for incompressible isotropic magnetohydrodynamic (MHD) turbulence a prediction for the inertial range scaling of the residual energy spectrum, E^{\rm R}_k=|E_k^{\rm kinetic}-E^{\rm magnetic}_k |\sim k^{-7/3} , is obtained. This scaling, while in contradiction to earlier theoretical results, is shown to be in agreement with high-resolution direct numerical simulations of nonhelical decaying MHD turbulence. The underlying phenomenology states a dynamic quasi-equilibrium of the small-scale turbulent dynamo and the Alfvén effect.