Numerical study of kinetic shear Alfvn instability in tokamak plasmas

Abstract

Kinetic shear Alfvn modes in tokamak plasmas (with or without temperature grad ient) in the full gyrokinetic limit are numerically investigated by using the integral eigenvalue equations. A new integration transformation is introduced in this work. This allows the growing and damping modes to be investigated. It is shown that, in the presence of ion temperature gradient (ITG), the threshold value of plasma pressure gradient for the shear Alfvn modes is well below that for ideal magnetohydrodynamic ballooning instability. It is also demonstrated in a m ore general sense that, without ITG, the former is identical with the latter. Th e electromagnetic instability is also found to exist in the second stable region of the ideal modes when a finite ITG is present. The results are compared with previous results of similar analyses for kinetic collisionless ballooning modes.