Studies on magnetic dynamics in RFX

The RFP configuration is maintained by an intrinsic dynamo mechanism associated to resistive MHD tearing modes. These dynamo modes are responsible for field line stochasticity and have a strong influence on plasma confinement. RFX results relevant to the subject are discussed both in terms of the influence of the magnetic boundary and of the characteristics of the RFP enhanced confimenement regimes. The dynamo modes are often locked in phase and to the wall, which spoils the stabilising effect of the conducting shell and leads to severe plasma-wall interactions. The driven rotation of the locked dynamo modes has been studied in RFX by means of a new Toroidal Field Modulation System. A rotating toroidally localised perturbation of the toroidal magnetic field couples to the modes and induces their rotation.