Influence of Toroidal Effects on the Stability of the Internal Kink Mode

Using the $\sigma$-stability technique, we study the stability of the internal kink mode in toroidal geometry. We show that there are two unstable regions separated by a stable one in a $\beta -q_c$ stability diagram. In one of these regions toroidal effects are stabilizing and in the other they are destabilizing. Discrepant results of previous analytical theories and experimental results are explained.