Cosmic Radio Noise Absorption in the Ionosphere: If Review of Results for the First Two Decades of Riometry at Low Latitudes

Abstract

In the past two decades since the original work of A. P. Mitra and C. A. Shain [<i>J. atmos. terr. Phys., </i> 4 (1953),204] on cosmic noise absorption, giving information about the ionospheric absorption of radio waves, the riometer technique has been used extensively, because of its importance in radio commutations and its implications in geophysical research. During IGY, a breakthrough in this technique resulted from the development of the riometer. This paper summarizes the state of knowledge, at the end of 1971, on cosmic radio noise absorption as applicable to low and equatorial latitudes, with emphasis on the Indian contribution towards the development and use of this technique. Due to the advantageous location of the Indian stations, riometer observations have provided meaningful results.