Feedback equations for the wall modes of a rotating plasma

Important magnetohydrodynamic instabilities, called wall modes, have growth rates that are determined by the resistivity of the wall that surrounds a toroidal plasma. Wall modes can be feedback stabilized, but plasma rotation modifies the theory of feedback stabilization and can even stabilize the m odes. This paper formulates the wall mode problem in a rotating plasma in a manner that can be incorporated in feedback stabilization codes. The formu lation utilizes the concept of a permeability, which relates the normal mag netic field on the surface of the plasma to the normal field produced by ex ternal circuits. The permeability provides all of the information about the plasma that is required to calculate the stability and the feedback stabil ization of wall modes. (C) 1999 American Institute of Physics. [S1070-664X( 99)01608-0].