The Ionosphere: Propagation Theory

Abstract

The propagation of low frequency electromagnetic waves in the atmosphere of the earth is a function of the degree of ionization of the constituent gases. The ionization is produced (Friedman, 1962; Ratcliffe, 1960) by the short-wave electromagnetic spectrum of the sun, X-rays and ultra-violet; and to some extent by particles, cosmic rays, meteors, and ion clouds from the sun. In general, a given ionizing agent will produce a layer with maximum ionization rate at some level, for the ionizing flux finds very few atoms or molecules to ionize at very great heights in the atmosphere. Then as the radiation penetrates more deeply, more ions sec⁻¹cm⁻³ are produced, but in this process the ionizing radiation is absorbed so that at lower heights the rate of ionization again falls to lower values, even though more ionizable molecules are present. Thus, any specific ionization process tends to produce a layer with a maximum ionization rate at some level.