Stability property of field-reversed configurations

Field-reversed configurations (FRCs) have been produced successfully by several formation techniques. This shows that FRCs are grossly stable. Nevertheless the tilt mode stability theories, which have been developed extensively for more than 15 years, cannot explain the gross stability observed in the exemptions. R. Kanno el al. examined the stabilizing effects of separatrix shape and current profile on the tilt mode by means of ideal MHD model without plasma flow. To represent the displacements, they used up to 3 basis functions (as a result, the eigen displacement was almost rigid). They found the MHD stable domain against the tilt mode for sufficiently hollow current profile and sufficiently racetrack separatrix shape. However in our recent study where the more accurate numerical technique was employed, we found that there was no such MHD tilt stable domain and found that the accurate numerical technique is necessary to study the stability property of FRCs. In this paper, for the purpose of offering a fundamental basis to understand FRC stability, we study the MHD stability properties of FRC eigenmodes with toroidal mode number l = 1 and intermediate toroidal mode numbers l = 2 - 30 in various FRCs. And we examine the stabilizing effect of the gyroviscosity. (author)