High and low frequency Alfvén modes in tokamaks

An analysis of the typical features of shear Alfven waves in tokamak plasmas in a frequency domain ranging from the high frequencies of the toroidal gap to the low frequencies is presented. The frequencies are comparable with the thermal ion diamagnetic frequency omega sub(*pi) and/or the thermal ion transit frequency omega sub(ti) identical with v sub(ti)/qR sub(0) where v sub(ti) is the ion thermal speed. Line bending can explain the finite beta stabilization of the electrostatic ITG. For increasing alpha ( beta ), the coupling to the electromagnetic shear Alfven branch also increases while the stabilizing influence of line bending diminishes. As a consequence, the stabilizing influence of the electrostatic ITG is expected to be strongest somewhere between alpha identical with 0 and alpha identical with alpha sub(crit).