EVOLUTION OF GAUSSIAN BEAMS IN THE NONUNIFORM EARTH-IONOSPHERE WAVE-GUIDE

In a uniform refraction waveguide the transversal width of a Gaussian beam oscillates with an approximately linearly growing amplitude. There exists a special set of initial data which eliminates its global diffraction divergency. We obtain an analogous result for a horizontally nonuniform Earth-ionosphere duct. By choosing initial elevation angle and operating frequency it is possible to concentrate a narrow radio wave beam at any given point of the Earth's surface. Our analysis is based on asymptotic integration of the ray equations which is outlined in appendix.