Nonlinear interactions in coronal heating

We present the first results of a 3D reduced MHD simulation that models the small-scale magnetic activity of coronal flux tubes. The equations are solved inside a box of dimensions l × l × L (axial direction), with an aspect ratio L/l of the order of 10. The box is initially threaded by a constant sinusoidal velocity field at one base (corresponding to one photospheric footpoint of the loop), of amplitude 1 km/s, (the axial Alfvén speed is about 1000 km/s), whereas the other footpoint is anchored, i.e., no photospheric motions are present. In the transverse directions, periodicity is assumed. Our numerical calculations show that the magnetic field lines change their topology continuously and often reconnect at small scales, forming typical coronal loop-like structures. Energy release events which provide a steady supply of energy are associated with the reconnection.