The tearing mode instability in a partially ionized plasma

The resistive tearing mode instability is a mechanism that in some cases will render unstable an MHD equilibrium of a plasma that is ideally stable, i.e., stable if no dissipative processes are taken into account. The tearing instability can be pictured as a tearing and reconnection of magnetic field lines that have a local reversal in direction, due to a slippage of field lines through the plasma. Since in the ideal approximation of a plasma the plasma is tied to the field lines, such slippage can only occur due to dissipative processes such as electrical resistivity (electron-ion collisions), or electron inertia effects. The discussion focuses both on the effects of neutral atoms and on the growth rate of the tearing instability. The amount by which the growth rate is reduced depends on the parameters of the problem, i.e., whether a solar problem or star formation is discussed. Formulas of the effective resistivity for specific ionization frequency are given.