Improved boundary layer analysis of forced magnetic reconnection due to a boundary perturbation

Linear boundary layer analysis of forced magnetic reconnection due to an externally imposed boundary perturbation has been reworked. This improved analysis introduces correct asymptotic matching to take into account the effect of inertia in the inner layer precisely, and adopts a time dependent boundary perturbation which is suitable for this analysis. The improved analysis demonstrates a new reconnection process and clarifies the role of stability against the tearing modes in the process. The initial evolution of this new reconnection process is characterized by some significant features which affect the subsequent evolution toward a fully reconnected state. One is that the reconnected flux increases on the same time scale as the boundary perturbation, which excludes the Sweet-Parker time scale obtained by use of the constant-psi asymptotic matching. Another is that an induced surface current on a resonant surface is in such a direction as to oppose the progress of the reconnection, because the equilibrium is stable against tearing modes in the absence of the boundary perturbation. (C) 2000 American Institute of Physics. [S1070-664X(00)00903-4].