Effect of large-scale inhomogeneities on the waveguide propagation of short radio waves

Short-wave transmission in the ionospheric waveguide in the presence of large-scale inhomogeneities is analyzed by solving the parabolic equation for waveguide propagation. Normal modes are approximated for the case of nonadiabatic disturbances of plasma density, and the mode diffusion-coefficient for quasi-periodic inhomogeneities is estimated. The estimation allows statistical and dynamic determination of mode-diffusion distances. The discreteness of the wave spectrum has a substantial effect on scattering only when the wavelength of the inhomogeneity approaches the beam-oscillation period.