Radio Propagation in a Plasma

Abstract

The behavior of radio waves in the terrestrial ionosphere has been meticulously described in several well-known texts and monographs, such as those by Rawer (1952), Mitra (1952), Ratcliffe (1959), Kelso (1964), Davies (1965, 1969, 1990), Wait (1970), Yeh and Liu (1972), Budden (1985), Kelley (1989). The purpose of this chapter is to review the fundamental processes whereby radio waves interact with the ionosphere, thereby laying a foundation for our understanding of the various radio techniques to be described in following chapters. Detailed derivations will not be given, since they are contained in the books cited above. Some of the most important aspects of the historical development of magnetoionic theory can be found in the works of Gillmor (1984). Salient points in the development of theories which describe the propagation of radio waves in the ionosphere will be included as each new topic is introduced. A very interesting bit of historical research on the origin of the term “ionosphere” was reported by Gillmor (1976), who concluded that Sir Robert Watson-Watt coined the term in a letter to the secretary of the British Radio Research Board in 1926. The acceptance of the term was aided by H. Plendl as “die Ionosphăre” and it came into wide use during the period 1932–1934 when Watson-Watt, Appleton, Ratcliffe, Dieminger, Ranzi, Martyn, Mitra, and others used the term in papers and books. Before the term “ionosphere” was accepted, it was variously called the Kennelly-Heaviside layer, the upper conducting layer, the ionized upper atmosphere, and other rather ponderous names!