On propagation of decametric-decimentric radiowaves under conditions of middle-latitude F-spread

Abstract

In this paper we analyze the influence of the large-scale inhomogeneous structure of a middlelatitude ionosphere with F-spread on the propagation of decametric-decimetric radiowaves. The phase fluctuations of short waves in the presence of middle-latitude F-spread are considered. A general integral formula for the frequency dispersion of phase fluctuations of short radiowaves during their propagation in a three-dimensional randomly-inhomogeneous ionosphere with an arbitrary electron-density distribution is obtained. For some of the simplest types of ray trajectories we find analytical solutions which allow us to obtain simple estimates of the frequency correlation of phase fluctuations of short radiowaves under conditions of middle-latitude F-spread. The amplitude fluctuations of short radiowaves under conditions of ionospheric F-spread are considered by the example of wave propagation with strong backscattering in a layered randomly inhomogeneous medium. It is shown that the presence of a strongly developed large-scale structure of electron density in a middle-latitude ionosphere with F-spread can cause reflected short-wave signals with relatively large delays and abnormally high fluctuation levels. The fluctuational and quasiregular effects accompanying the transionospheric propagation of metric-decimetric radiowaves are discussed. In particular, it is shown that under conditions of middle-latitude F-spread the inhomogeneous structure of the ionospheric plasma does not have a significant influence on the fluctuational or quasi-regular propagation characteristics of decametric-decimetric radiowaves.