A Criterion for Stability of Surface-Preserving Modes in Axisymmetric Toroidal Plasmas

Abstract

A stability criterion for surface-preserving modes in closed-line systems in axisymmetric toroidal plasmas is derived from an energy principle. The criterion is compared with a criterion for localized modes in a plasma with closed-line field. It is found that there exists a certain discontinuity between those criteria. The stability criterion for the surface-preserving modes is diagrammed by elliptic quadratic curves for toroidal plasmas with a large aspect ratio.