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

Linear boundary layer analysis of forced magnetic reconnection due to an ex ternally imposed boundary perturbation has been reworked. This improved ana lysis introduces correct asymptotic matching to take into account the effec t of inertia in the inner layer precisely, and adopts a time dependent boun dary perturbation which is suitable for this analysis. The improved analysi s demonstrates a new reconnection process and clarifies the role of stabili ty against the tearing modes in the process. The initial evolution of this new reconnection process is characterized by some significant features whic h 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 c urrent on a resonant surface is in such a direction as to oppose the progre ss of the reconnection, because the equilibrium is stable against tearing m odes in the absence of the boundary perturbation. (C) 2000 American Institu te of Physics. [S1070-664X(00)00903-4].