Forced reconnection, current sheets, and coronal heating

The formation of current sheets in the solar corona is investigated by a simple model in which forced reconnection occurs due to the perturbation caused at the photospheric boundary by footpoint motion. The time dependence of the process is considered by means of an initial-value calculation. It is found that on the Alfvénic time scale, current sheets tend to develop with an amplitude that increases linearly with time. The effect of resistivity becomes important subsequently, and the reconnected flux at the separatrix increases quadratically with time. In the nonlinear phase, helicity-conserving islands support current sheets, and the rate of reconnection is given by a modified Sweet-Parker model. Implications for coronal heating are discussed.