Identification of island-induced Alfvén eigenmodes in a reversed field pinch

The modification of the shear Alfven spectrum due to a core resonant magnetic island is used to explain the Alfvenic activity observed on the Madison symmetric torus (MST) reversed-field pinch during neutral beam injection. Theoretical studies show that the Alfven continua in the core of the island provide a gap in which the observed Alfvenic bursts reside. Numerical simulations using a new code called SIESTAlfven have identified the bursts as the first observation of an island-induced Alfven eigenmode (IAE) in an RFP. The IAE arises from a helical coupling of harmonics due to the magnetic island.