Dissipation and intermittency in MHD turbulence

P.D. MININNI

Marseille, Francia

Workshop; Dynamos from numerical and experimental point of view; 2009

CIRM, CNRS

We present an analysis of data stemming from numerical simulations of decaying magnetohydrodynamic (MHD) turbulence up to grid resolution of 15363 points and up to Taylor Reynolds number of 1200. The initial conditions are such that the initial velocity and magnetic fields are helical and in equipartition, while their correlation is negligible. Analyzing the data at the peak of dissipation, we show that the dissipation in MHD seems to asymptote to a constant as the Reynolds number increases, thereby strengthening the possibility of fast reconnection events in the solar environment for very large Reynolds numbers. Furthermore, intermittency of MHD flows, as determined by the spectrum of anomalous exponents of structure functions of the velocity and the magnetic field, is stronger than for fluids, confirming earlier results; however, we also find that there is a measurable difference between the exponents of the velocity and those of the magnetic field, as observed recently in the solar wind. Finally, we discuss spectral scaling laws and anisotropies that arise in this flow, considering that they may correspond to one of a possible variety of energy spectra for MHD turbulence.