  Context. We investigate the statistics of the spatial and temporal
distribution of the coronal heating in a three-dimensional magneto-
hydrodynamical (3D MHD) model. The model describes the temporal evolution of
the corona above an observed active region. The model is driven by photospheric
granular motions which braid the magnetic field lines. This induces currents
and their dissipation heats the plasma. We evaluate the transient heating as
subsequent heating events and analyze their statistics. The results are then
interpreted in the context of observed flare statistics and coronal heating
mechanisms. Methods. To conduct the numerical experiment we use a high order
finite difference code which solves the partial differential equations for the
conservation of mass, the momentum and energy balance, and the induction
equation. The energy balance includes the Spitzer heat conduction and the
optical thin radiative loss in the corona. Results. The temporal and spatial
distribution of the Ohmic heating in the 3D MHD model follow a power law and
can therefore be explained by system in a self-organized critical state. The
slopes of the power law are similar to the results based on flare observations.
We find that the corona is heated foot point dominated and the coronal heating
is dominated by events called nanoflares with energies on the order of 1017 J.
