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Abstract

The effect of mass flows on ideal stability of cylindrical equilibria is investigated using both the magnetohydrodynamic (MHD) and guiding centre (GCP) plasma models. The flows modify the local criterion for instability at the resonant surface where "bf k"cdot"bf B"=0. A stability limit is found in the MHD picture at a critical velocity where the shear of the flow balances the propagation of the slow wave along the magnetic field. Just below the critical velocity there is instability independent of the pressure gradient. Above the critical speed the Suydam modes are stable, but an infinite sequence of unstable modes still exists with frequencies accumulating toward the edge of the slow wave continuum at non-zero Doppler shifted frequency. The stability limit is removed in the guiding centre model, due to the more realistic kinetic treatment of the parallel motion, which smooths the resonance between flow and sound waves. Numerical results for a simple test case are presented, showing that in the GCP model sheared equilibrium flows can stabilize localized modes.

Additional information

Authors: IACONO R, CENTRE DE RECHERCHES EN PHYSIQUE DES PLASMAS, ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE, CH;BONDESON A CENTRE DE RECHERCHES EN PHYSIQUE DES PLASMAS, ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE, CH, CENTRE DE RECHERCHES EN PHYSIQUE DES PLASMAS, ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE, CH
Bibliographic Reference: WORKSHOP ON THEORY OF FUSION PLASMAS, VARENNA/I, AUG. 24-28, 1987, PUBL. 1987, BY: SOCIETA ITALIANA DI FISICA
Record Number: 1989126085400 / Last updated on: 1989-05-01
Category: PUBLICATION
Available languages: en