Plasma relaxation to force-free states

Considering a plasma subject to resistive processes according to the Ohm-Maxwell equations, it is shown that a functional of the magnetic configuration exists, which is stationary and maximum for a particular force-free equilibrium. Outside equilibrium of the functional is an increasing function of time. From these properties one derives, under proper conditions, the resistive evolution of the plasma towards a limited class of equilibria which includes the force-free states. (author)