Model investigations of radio wave propagation in the lower ionosphere to determine electron densities from MF pulse sounding

Abstract

In this paper full‐wave calculations are described to investigate the propagation of MF radio waves in the range from 255 to 950 kHz in the lower ionosphere. The method of investigation makes use of matrix multiplications with the ionosphere divided into homogeneous layers of 100‐m thickness. The model calculations provide conclusions from MF pulse sounding results on electron density and collision frequency profiles in the height interval from 50 to 100 km. The diurnal variation of electron density in the lower ionosphere is presented. Reflections observed from heights of about 75 and 87 km during the day are shown to be produced by steep gradients of electron density.