Auroral absorption of HF radio waves in the ionosphere: A review of results from the first decade of riometry

In the decade since the International Geophysical Year, information about the ionospheric absorption of radio waves during periods of auroral and magnetic disturbance has been greatly increased by the use of the riometer technique. Such studies are important for their geophysical implications as well as in direct applications to radio propagation. The purpose of this paper is to summarize the state of knowledge of auroral radio absorption at about the end of 1968, and at the same time to give the major references through which the reader may be enabled to study any particular questions in greater depth.