Ray tracing in weakly nonlinear moving media

Electromagnetic ray propagation is discussed for weakly nonlinear dispersive media. Specialization to periodic waves justifies the use of a self-excitation model and facilitates the construction of a complete system of ray equations. The solution describes the evolution of frequencies, propagation vectors and amplitudes along the ray path. The formalism may be extended to include the case where a velocity field exists. This is based on special relativity and the Minkowski model for the electrodynamics of moving media. It is assumed that the velocity field varies slowly in space and time. The results are relevant to propagation problems in weakly nonlinear plasmas and optical media.