FM pulses in stratified isotropic plasma

The problem of plane FM pulse propagation in an inhomogeneous plasma that varies slowly in one space dimension is formulated and solved asymptotically. The solution is then applied to a particular example with an exponential variation of plasma frequency for which the ray equations can be solved in closed form. By a technique based on the space-time ray structure for an impulsive point source and a coordinate transformation involving time inversion, it is shown how to synthesize FM pulses capable of producing pulse compression. Numerical results obtained for the focal region define the compression of signals which are shown to be related to three distinct ray configurations.