Low-<i>n</i> shear Alfvén spectra in axisymmetric toroidal plasmas

Abstract

In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown both analytically and numerically that the toroidicity not only breaks up the shear Alfvén continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfvén eigenmodes with frequencies inside the continuum gaps. Potential applications of the low-n toroidicity-induced shear Alfvén eigenmodes on plasma heating and instabilities are addressed.