Variational principle and comparison theorem for the kinetic stability of two-dimensional Vlasov equilibria

Abstract

Distribution functions of the form F ( H . pI) are used to describe two-dimensional high j l plasmas with purely axial current. Both species, electrons and singly charged ions, are treated kinetically. Vacuum fields and effects due to neutral lines. finite gyro radii, particle trapping and electrostatic fields are included in the study. F o r i independent perturbations, a variational principle, which is simple to use in applications. is derived. Pressure profiles fulfilling the corresponding stability criterion are found in Extrap and in : pinch geometry. For a large class of displacements. the system is kinetically stable if it is M H D stable.