The propagation of radio waves in a horizontally stratified ionosphere was made the subject of an earlier book by the author published in 1961. The present book covers roughly the same topics as the earlier book but the treatment is necessarily different due to the advances in the subject. The author cites three main reasons for this: the use of space vehicles and rockets enabling the top-side of the ionosphere to be studied; the advance of aplasma physics; and the use of computers.
Whilst the main thrust is concerned with radio waves the acoustics engineer will find parallels within his own field. Thus the author comments that in the study of the propagation of such waves in an ocean and its bed the system is often assumed to be horizontally stratified because of the temperature, salinity and other properties which depend in depth. Indeed for such waves the ocean bed can behave like an inverted ionosphere though sound waves are not usually dispersive. The material will also be of interest to workers in the seismic field where waves propagating in continuously varying stratified regions of the earth's crust are studied.
The first six chapters of the book are concerned with descriptions of, and equation formulation for, the ionospheric medium. The remainder of the book which is contained within chapters 7-19 will be ofinterest to acoustic engineers also. Therein are mathematical topics covered in some detail and these include WKB approximations of the phase integral method, Airy integral functions and integration by steepest descents. These will be found in chapters 7-9. Ray tracing in a loss free stratified medium appears in chapter 10.
Plane wave reflections are treated in chapter 11 though the acoustics worker will find the treatment of spherical wave-fields including pulsed waves of particular interest. Chapter 12 deals with ray propagation and reflection in an isotropic ionosphere. Chapter 14 is concerned with ray tracing in a generally varying medium where the signal intensity along a ray tube is studied. The remaining chapters 15-19 are concerned with problems in which the approximations of ray theory cannot be made so that full wave solutions of the governing ditterential equations are required.
The book is written for the physicist and although mathematical rigour is achieved, the stress is always on physical understanding. Acoustic engineers with a theoretical bias will no doubt find the book particularly useful as a reference. There are some 600 pages and a long reference list which covers dates up to 1984.
B. S. WESTCOI'r