Reversed Shear Alfvén Eigenmodes: Experiment, Simulations and Theory
Analytical theory and ideal MHD simulations are applied to interpret and understand Alfvén eigenmode activity that can exist at the shear revearsal point in the magnetic safety factor, the Reversed Shear Alfvén Eigenmodes (RSAE). The frequency behavior and the radial mode structure is studied for RSAEs associated with the TAE gap. From theory and simulations it was predicted that RSAE-like modes can also exist in higher order gaps in the Alfvén continuum. Experimental evidence is shown for RSAEs associated with the NAE gap.