Guiding properties of a smoothly inhomogeneous layer and diffraction excitation of ionospheric waveguides

Abstract

The author investigates the diffraction of a spherical wave by a smoothly inhomogeneous layer in which a waveguide zone is situated behind a barrier of finite weight. An expression is derived for layer-guided waves generated outside the layer by energy transfer between the waveguide and the external homogeneous half space. Certain properties of these waves are investigated. It is shown that, since the losses associated with energy leakage from the waveguide across the barrier are more significant than the initial wave amplitude at large distances, the role of principal (optimal) mode passes from one mode to another at a lower level in the potential well (waveguide) with increasing distance. The problem of diffraction excitation of ionospheric waveguides in ultralong-range propagation of short radio waves is considered as an example. The results are discussed and compared with published experimental data.