Stability of two-dimensional collision-free plasmas

The stability of plasma equilibria is analysed in the framework of two-dimensional Vlasov theory, where the perturbations are constant along the direction of the equilibrium current. The method makes use of several general properties of the equations, thus covering a rather large class of different configurations. Several necessary and sufficient stability criteria and an expression for the growth rates are derived. In particular, the results are applicable to equilibria containing neutral points. A number of earlier results (e.g. the tearing mode) are recovered by appropriate specialisation.