Magnetohydrodynamic turbulence of coronal active regions and the distribution of nanoflares

We present results from numerical simulations of an externally driven two-d imensional magnetohydrodynamic system over extended periods of time, used t o model the dynamics of a transverse section of a solar coronal loop. A sta tionary forcing was imposed to model the photospheric motions at the loop f ootpoints. After several photospheric turnover times, a turbulent stationar y regime is reached that has an energy dissipation rate consistent with the heating requirements of coronal loops. The turbulent velocities obtained i n our simulations are consistent with those derived from the nonthermal bro adening of coronal spectral lines. We also show the development of small sc ales in the spatial distribution of electric currents, which are responsibl e for most of the energy dissipation. The energy dissipation rate as a func tion of time displays an intermittent behavior, in the form of impulsive ev ents, that is a direct consequence of the strong nonlinearity of the system . We associate these impulsive events of magnetic energy dissipation with t he so-called nanoflares. A statistical analysis of these events yields a po wer-law distribution as a function of their energies with a negative slope of 1.5, consistent with those obtained for hare energy distributions report ed from X-ray observations. A simple model of dissipative structures, based on Kraichnan's theory for MHD turbulence, is also presented.