Relations Between the Bearing and the Amplitude

Abstract

In the preceding section, the scattering of waves by irregularities in the ionosphere was discussed mainly in terms of one passage of an initially plane wave through the ionosphere. Under the conditions in which we are most interested here, i.e. long-distance radio propagation, many encounters with the ionosphere will have occurred. Although none of these will be a passage right through the ionosphere, most being a double passage at an oblique angle through that part of the ionosphere which lies below the reflection level of the wave, the picture of an incident plane wave becoming a plane wave together with a series of scattered components will still hold. The scattered components will interfere and produce changes in the amplitude of the wave received at the ground, so that the received wave exhibits two types of fluctuation. The first of these, which arises from the corrugation of the wave front (the phase fluctuations) can be investigated if a direction-finder which can observe rapid fluctuations in the wave-normal direction is employed. The second type of fluctuation is the amplitude fading of the wave.