MHD phenomena in advanced scenarios on ASDEX Upgrade and the influence of localized electron heating and current drive

On the one hand. MHD instabilities in advanced tokamak scenarios are favourable as they can contribute to thc stationarity of the current profiles and act as a trigger for the formation of internal transport barriers (ITBs). lit particular, fishbone oscillations driven by fast, particles arising front NBI are shown to trigger ITBs in low and reversed magnetic shear discharges. During the whistling down period of the fishbone oscillation the transport is reduced around the corresponding rational surface, leading to all increased pressure gradient. This behaviour could be explained by the redistribution or the resonant fast particles resulting lit a sheared plasma rotation due to the return current in limit, bulk plasma, which is equivalent to a radial electric field. Oil the other hand, MHD instabilities, limit the accessible operating regime. Ideal and resistive MED modes such as double tearing modes, infernal modes and external kinks degrade the confinement or even lead to disruptions in ASDEX Upgrade reversed shear discharges. Localized electron cyclotron heating and current drive are shown to significantly affect the MHD stability of this type of discharge.