Stabilization of the Mercier modes in a tokamak by toroidal plasma rotation

Citation
C. Wahlberg et A. Bondeson, Stabilization of the Mercier modes in a tokamak by toroidal plasma rotation, PHYS PLASMA, 8(8), 2001, pp. 3595-3604
Citations number
29
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
PHYSICS OF PLASMAS
ISSN journal
1070-664X → ACNP
Volume
8
Issue
8
Year of publication
2001
Pages
3595 - 3604
Database
ISI
SICI code
1070-664X(200108)8:8<3595:SOTMMI>2.0.ZU;2-Y
Abstract
The stability of localized modes (Mercier modes) in a tokamak with a toroid ally rotating plasma is analyzed within the framework of compressible, idea l magnetohydrodynamics. For equilibria with large aspect ratio, poloidal be ta value of order unity, and isothermal magnetic surfaces, it is found that sonic, toroidal rotation provides a strongly stabilizing effect for the Me rcier modes, similar to the stabilization recently found for the internal k ink mode in a rotating plasma [Wahlberg and Bondeson, Phys. Plasmas 7, 923 (2000)]. A finite oscillation frequency (Brunt-Vaisala frequency), of the o rder of the sound frequency, is shown to be associated with each magnetic s urface. If Gamma >1, where Gamma is the exponent in the equation of state, the rotation transforms the Mercier instabilities to stable oscillations at the local Brunt-Vaisala frequency associated with the magnetic surface whe re the mode is located. If the plasma satisfies an isothermal equation of s tate (Gamma =1), however, the stability of the Mercier modes becomes sensit ive to the profile of the toroidal flow. In this case, the rotation is foun d to be stabilizing if the kinetic energy density of the rotation is an inc reasing function of the minor radius. In the opposite case, the rotation is destabilizing unless the pressure profile is much more peaked than the kin etic energy density profile. (C) 2001 American Institute of Physics.