New Alfvén Continuum Gaps and Global Modes Induced by Toroidal Flow

Continuous magnetohydrodynamic (MHD) spectra in tokamaks with toroidal rotation are studied. In the corotating frame, the linear perturbations experience Coriolis and centrifugal effects. The latter create Alfvén frequency gaps on rational surfaces resonant with the perturbations. New global eigenmodes are located inside these gaps. These modes may be used for MHD spectroscopy. In contrast to the usual gaps and toroidal Alfvén eigenmodes, the new flow-induced gaps and global modes are in the low frequency range so that they will have important implications for stability as well.