Magnetic field line reconnection in weakly ionized plasmas

We present the results of theoretical studies of the magnetic field line reconnection in weakly ionized plasmas. We investigate the propagation of small amplitude magnetohydrodynamic (MHD) waves near critical lines of the magnetic field and show the occurrence of the pile-up of electric current. This magnetic collapse is described by self-similar solutions that demonstrate the formation of singular structures in the vicinity of the magnetic field separatrix surfaces. We obtain the growth rate of the tearing mode instability of the current sheet and present a solution of the Taylor problem for a slab of a weakly ionized plasma. We have found the reconnection rate and the dimensionless parameters that describe the relative role of nonlinearity and dissipation effects near critical points. We present results of the MHD computer simulation of two-loop coalescence that show the dependence of reconnection on the value of ion-neutral drift.