Drift-wave eigenmodes in toroidal plasmas

Abstract

The eigenmode equation describing ballooning drift waves in toroidal plasmas is investigated both analytically and numerically. Two branches of eigenmodes are identified. One is slab-like and the other is a new branch induced by finite toroidal coupling. The slab-like eigenmodes correspond to unbounded states and experience finite shear damping. The toroidicity-induced eigenmodes, however, can become local quasi-bounded states with negligible shear damping. Both branches of eigenmodes may exist simultaneously. The corresponding analytical theories are also presented.