Resistive ballooning modes

Resistive ballooning modes are analyzed in the neighborhood of the magnetic axis. There are two mode branches, one connecting to the usual tearing mode and the other to the magnetohydrodynamic ballooning mode. Unstable modes satisfy the generalized tearing dispersion relation. Resistive ballooning modes can be unstable for a wide range of beta, but may be stabilized by interchange effects and finite sound speed. The analytic results are in qualitative agreement with low mode number numerical solutions.