Threshold for explosive reconnection of crossed dynamic field lines in a plasma slab

A nonlinear theory is derived for the drift-tearing instability in slab geometry in the presence of crossed magnetic field lines, taking into account their diffusion across magnetic surfaces destroyed by the modes that are excited. Because the Cherenkov interaction between the electrons and a mode is weakened due to the rapid diffusion from the region within which the longitudinal electric field of the drift-tearing mode is localized, the mode grows explosively. Inclusion of the longitudinal thermal motion of the ions and electrons along the magnetic field lines yields a stabilizing contribution to the dispersion relation and thus determines the threshold value of the gradient in the electric current of the plasma for which explosive growth of the instability accompanied by reconnection of the magnetic field lines becomes possible. 8 refs., 1 fig.,