The beam tracing technique describes electromagnetic wave beam propagation
in the short wavelength limit, including diffraction effects, not described
by the usual geometric optics. It involves a set of ordinary differential
equations: a central or reference ray is determined and around this the bea
m profile and the shape of the phase front are calculated. Here, these equa
tions are obtained for a Gaussian wave beam. Analytic solutions in an inhom
ogeneous magnetized plasma are given for perpendicular propagation in a sla
b geometry. The beam is found to show a strong deformation of its cross sec
tion due to the anisotropy of the medium. The rotation of the cross section
and that of the curvature of the phase front are discussed. (C) 1999 Ameri
can Institute of Physics. [S1070-664X(99)00701-6].