Spectral Studies of Fading from Radio-Satellites; and Ionospheric Irregularities

Abstract

Properties of the irregularities in ionospheric refractive index responsible for radio-satellite scintillation have been found from a spectral analysis of spaced-receiver records. The spaced-receiver experiments were operated over a two year period at mid-latitude and sub-auroral locations, using the 40 MHz transmissions of satellite BE-B. The important results of the analysis relate to the diurnal, seasonal, and latitude variations of the irregularity heights, and the latitude behaviour of irregularity size. Night-time scintillation is usually produced in the F-region at all times of the year, and in particular in the top-side of the F-region in the southern summer. Day-time scintillation is rare at mid-latitudes; at sub-auroral. latitudes it may be produced at any height. The night-time height distributions show a constancy of height with latitude in summer and winter, although there is a slight increase poleward in average autumn-spring night-time heights. Average irregularity size shows a decrease with increased latitude. The occurrence of high heights at sub-auroral latitudes is related to magnetic activity, and this relationship, together with the form of seasonal variations of irregularity height, suggests that irregularity height variations are directly related to atmospheric density variations. This thesis includes seven chapters. Chapter 1 introduces the subject; Chapter 2 relates scattering theory and spectral analysis; Chapter 3 describes the experimental work Chapter 4 describes the data reduction; the results of, the analysis are given in Chapters 5 and 6, and these results are interpreted in Chapter 7. Chapters 1, 3, 5, 6, 7 form a logical sequence which the reader is invited to follow initially. The more formal material of, Chapters 2 and 4 might be covered at a later reading.