A comprehensive analysis of the stability properties of the appropriate kinetically generalized form of MHD ballooning modes, together with the usual trapped-particle drift modes, is presented. The calculations are fully electromagnetic and include the complete dynamics associated with compressional ion acoustic waves. Trapped-particle effects, together with all forms of collisionless dissipation, are taken into account without approximations. The influence of collisions is estimated with a model Krook operator. Results from the application of this analysis to realistic tokamak operating conditions indicate that unstable short-wavelength modes with significant growth rates can extend from /J = 0 to values above the upper ideal-MHD critical beta associated with the ‘second stability regime’. Since the maximum growth rates of the relevant modes appear to vary gradually with beta, these results support a ‘soft’ beta-limit picture involving a continuous (rather than abrupt or ‘hard’) modification of anomalous transport already present in low-beta tokamaks. However, at higher beta the increasing dominance of the electromagnetic component of the perturbations indicated by these calculations could also imply significantly different transport scaling properties.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Condensed Matter Physics