The reflection of radio waves from ionospheric irregularities, at vertical incidence

Abstract

When a radio wave is reflected at vertical incidence from a horizontally stratified ionosphere which contains random irregularities of electron density, the downcoming wave consists of a cone of rays apparently scattered back to the receiving point by the irregularities. However, there has hitherto been no clear description of how the scattering occurs. It is suggested here that the oblique rays are partially or totally reflected in the backwards direction from irregularities situated at or near the apex of the ray trajectories. The width of the angular spectrum of the downcoming wave is determined by the intensity ΔN/ N of the irregularities. ΔN/ N is deduced to be of the order of 0.01. The rays received at the ground appear to come from a virtual diffracting screen located at the virtual height of reflection. p ]When field-aligned irregularities are present, reflection occurs where the rays are perpendicular to the elongation. This restricts the angular spectrum in the meridian plane and produces a north-south elongation of the ground pattern with an axial ratio r = cosec I, where I is the magnetic dip. An explanation is given of why a ground pattern produced by transmission is more elongated than one produced by reflection.