Investigation of the localized co-interchange instabilities in a rotamak plasma

If the rotamak is regarded as a spherical field-reversed mirror then, according to conventional ideal MHD analysis, it should be unstable to co-interchange modes localized near the vortex point of the magnetic field. It is shown that to study these instabilities in a typical rotamak plasma, the Hall term in Ohm's law cannot be ignored. The effect of the Hall term on the ideal MHD analysis of co-interchange modes is investigated and a stability criterion is derived.