Excitation of Alfvén-like Modes by Large Resonant Magnetic Perturbations in Ohmic Discharges
Alfvénic modes, as determined by their frequency scaling, have been detected in ohmic discharges at TEXTOR and FTU. Recently they have also been observed in limiter plasmas at JET. They appear in the presence of large 2/1 tearing modes or strong resonant magnetic perturbations. Their drive by thermal ions distinguishes them from other Alfvénic modes, such as Toroidal Alfvén Eigenmodes (TAE). A consistent cross-machine scaling indicates a robust frequency dependence on plasma parameters.