The properties of the frequency splitting of the axisymmetric magnetoacoustic wave and an application to current profile diagnosis

In the presence of finite plasma current, the axisymmetric (m=0) magnetoacoustic wave resonance exhibits a frequency splitting for finite toroidal mode number (n≠0) between oppositely directed traveling waves. Calculations are presented that demonstrate that Δ(1/f), the difference between the inverse resonance frequencies, is closely proportional to known moments of the plasma current profile and, in the limit where the radial wave number is much larger than the parallel wave number, is independent of the plasma mass density and its profile. A discussion of the observability of the splitting for the purpose of current profile diagnosis, given the theoretical and experimental data available, is also presented