Linear gyrokinetic theory and computation of the gyrocenter motion based on the exact canonical variables for axisymmetric tokamaks

Abstract

Linear gyrokinetic theory based on the Lie-transform perturbation method is presented in terms of the exact canonical variables. In the linear drift approximation, it is shown that the gyrocenter equations of motion based on the canonical variables are equivalent to the usual guiding-center equations of motion. A numerical code is developed to advance the gyrocenter motion in terms of the exact canonical variables with arbitrary perturbations. It is found that a static magnetic island in a tokamak has little effect on the trapped particle orbits due to the conservation of the longitudinal invariant; and it induces the island structure of passing particle orbits due to the fact that the longitudinal invariant for the passing particles is broken by the asymmetric perturbation.