The Normal D Region of the Ionosphere

The general theory of low-frequency sounding in the lower ionosphere is discussed in order to indicate the radio transmission characteristics which a D-layer model must satisfy. D layers based on the fundamental physical processes from 60 to 90 km, which have been presented up to now, have not been completely satisfactory. There is indication that the more accurately determined values of fundamental parameters now available, such as reaction rates, will lead to a more satisfactory model.