Solution near the wavefront of transient fields in inhomogeneous dispersive media

Uniform asymptotic representations, valid in the vicinity of the wavefront, are derived for transient fields propagating in an inhomogeneous dispersive medium. When the space-time ray equations for these fields can be solved explicitly, the uniform representations yield explicit expressions in the space-time variables; otherwise, the representations involve a parameter which can, however, be eliminated under more restrictive conditions. The results are applied to plane pulse propagation in a plane stratified plasma with exponential variation of electron density, for which the space-time ray equations can be solved in closed form; in this case, the asymptotic representation is found to yield the known exact solution.