Abstract
The spontaneous formation of magnetohydrodynamic (MHD) equilibrium profiles in toroidal current‐carrying plasmas has been discussed for tokamaks, reversed‐field pinches (RFP’s), and also for their intermediate states ultra‐low q’s (ULQ’s). The significance of m (poloidal mode number)=1 fluctuations causing a shift of the magnetic axis is stressed. The characteristics of MHD relaxation have been studied in comparison with classical diffusion. The dynamics of ULQ’s is shown to illustrate the characteristics of both dissipative processes. A global‐mode stable ULQ is observed to be produced through MHD relaxation, and then to be deformed, in a longer time scale, by classical diffusion which destabilizes the stable profile.