Theory of the M = 1 mode in high temperature plasmas

The linear and nonlinear properties of the m = 1 kink mode have been investigated numerically and analytically within two fluid theory taking into account diamagnetic drifts, ion viscosity μ and plasma diffusion kappa in addition to resistivity eta. In the regime of strong diamagnetic effects, ωsub(*)/γsub(T) > 1, the linear growth rate is a very sensitive function of kappa, being strongly reduced and even negative around kappa approx. > eta. Nonlinearly the mode is found to saturate at finite amplitude in contrast to the resistive regime ωsub(*)/γsub(T) < 1, where complete reconnection occurs. The main stabilizing effect is a nonlinear azimuthal flow near the resonant radius; hence there is a strong dependence on μ. A quasi-linear theory can explain the main numerical results. Brief application to tokamak experiments is given. (orig.)