Resistive interchange instabilities in a tokamak with a viscous high-β plasma

A theory is derived for resistive interchange instabilities in a tokamak with a viscous high-β plasma. It is found that the fundamental mode of resistive interchange perturbations may be unstable only if there is a vacuum magnetic hill, and the plasma pressure is not too high. Such perturbations are not stabilized by viscosity. In contrast with this case, the resistive interchange perturbations of level l (l = 1, 2, ...) may be unstable in a high-β plasma if there is a magnetic well, but they stabilize at a high viscosity. The role played by compressibility in resistive interchange modes is studied. The results show that most of the perturbations studied here may be regarded as incompressible