Absorption of radio waves reflected at vertical incidence as a function of the sun's zenith angle

Abstract

The diurnal variation of ionospheric absorption is related to the sun's zenith angle. The absorption values for this study were obtained from the continuous automatic fieldintensity recordings made at the Central Radio Propagation Laboratory on two frequencies. Because of proximity of the receiving station to the transmitting station, reflections are obtained at nearly normal incidence. An analysis of data covering a period of 3 years indicates that little error is introduced by assuming a linear dependence of absorption upon the cosine of the sun's zenith angle.