MHD stability of nonlocal quasiflute modes in closed magnetic confinement systems
Il'gisonis V. I., Pastukhov V. P.
An analytic minimization of a potential-energy functional of MHD perturbations in a finite-pressure plasma is carried out. In closed systems, nonlocal quasiflute modes can develop. They turn out to be more dangerous than localized perturbations. As an example, a necessary and sufficient condition for MHD stability is derived for confinement systems of the DRAKON type. This condition is sufficient for arbitrary current-free paraxial systems with circular magnetic surfaces.