Measurements of the absorption of wireless waves in the ionosphere

Abstract

In most of the investigation which have been made on wireless waves reflected from the ionosphere the experiments have been so designed as to provide information concerning the ionization density at different levels. The experimental data sought in such cases are usually critical penetration frequencies and equivalent heights of reflection. If, however, the amplitude of the downcoming waves is also observed, and the total absorption measured, it is possible to obtain information about the frequency of collision between electrons and molecules at different heights in the ionosphere. The measurements described in the present paper have been made so as to provide the latter type of information, and in particular to give evidence concerning the location of that part of the ionosphere which is of importance in producing absorption. For this purpose it is necessary to measure the absolute value of the absorption suffered by the wave, so that results on different wave-lengths may be compared. The methods which we have employed in making these measurements are described in § 2 and the results are discussed in § 4. The theoretical results which are used in § 4 are reviewed shortly in § 3. Most of the measurements discussed in this paper have been made on wave-lengths less than 200 m; a few measurements made with longer waves are discussed in § 6.