Propagation of a Gaussian beam in a nonhomogeneous plasma

The asymptotic theory of Choudhary and Felsen [IEEE Trans. Antennas Propag. AP-21, 827 (1973)] on the propagation of scalar inhomogeneous waves in two-dimensional isotropic media is extended to the case of three-dimensional vector fields. The theory is applied to the propagation of Gaussian beams in nonhomogeneous media. The wave trajectory equations are then reformulated for anisotropic media and used for tracking a Gaussian beam in a tokamak plasma.