Coronal magnetohydrodynamic evolution driven by subphotospheric conditions

We consider the approach to the theory of formation, evolution, and major disruption of coronal twisted flux ropes, in which subphotospheric structures play a crucial role. We set a boundary value problem in the corona in which the boundary conditions at the photospheric level are determined by a simple kinematic model describing the rising of a tube throughout the convection zone. In addition to peculiar features like the existence of areas of flux concentration on the lower boundary and the bending of the polarity inversion line, we find that the coronal configuration suffers a transition from arcade to rope topology and (later) a transition from a slow quasistatic evolution to a dynamic nonequilibrium one, both these critical phenomena occurring during the phase of decrease of the net photospheric flux. There is a continuous injection of magnetic helicity into the corona, and the magnetic energy remains smaller than that of the corresponding open field. Contrary to what has been observed in some other simulations, the formation of the equilibrium flux rope prior to the disruption is not associated with some reconnection on the "photospheric" surface. This may possibly suggest the utility of different observational diagnostics.