Return of Radio Waves from the Middle Atmosphere

Abstract

WE are glad to be able to confirm and amplify the indications given by Prof. R. C. Colwell and A. W. Friend in the letter which appeared in NATURE of May 9. One of us, in his address, as chairman, to the Wireless Section of the Institution of Electrical Engineers¹, has reported briefly on the initial stages of work for the Radio Research Board undertaken recently at Orfordness, a site the isolation of which permitted the use of substantial powers in short-duration pulses for the closer study of the lower regions of the ionosphere. In addition to the sporadic reflections from levels between 85 km. and 100 km. then reported, we have had under intermittent observation the very complex echo-systems which result from the return of radio waves from heights between 6 km. and 60 km.