Localized resistive modes in the circular Tokamak

Localized resistive modes (resistive interchange and resistive ballooning modes) are investigated for self-consistent Tokamak equilibria which have circular cross-sections near the magnetic axis. The second region of stability (which is stable with respect to ideal ballooning modes at high poloidal beta βp) proves to be unstable when resistive effects are taken into account as well. In the low βp stability region, the stability boundaries are shifted toward lower βp values. The magnitude of the shift depends on the degree of localization of the perturbation around the field line, highly localized perturbations being the most unstable ones. For negative values of βp (pressure increasing outward) equilibria exist which are stable with respect to both ideal and resistive interchange and ballooning modes. (orig.)