MHD behaviour in a resistive-shell reversed-field pinch

The magnetic field on the external surface of the resistive shell has been measured in the T2 reversed-field pinch. Wall-locked internally-resonant modes, which produce toroidally localized (Delta phi similar to 60 degrees), large quasi-stationary m = 1 radial held perturbations are observed. At the position of the wall-locked mode, m = 0 perturbations are generated in local dynamo events and produce a large stationary toroidal field perturbation: The m = 0 modes rotate toroidally from the location where they are produced and diminish within one toroidal turn. Numerical, resistive magnetohydrodynamic simulations verify the correlation between a m = 1 radial held and a toroidal held perturbation.