Downward Electron Flux at 1,000 km Altitude from Electron Content Measurement at Mid-latitudes

Abstract

IN a previous paper¹, describing diurnal variation of ionospheric electron content during November–December, 1961, at mid-latitudes, we reported the existence of a secondary maximum of ionization content below 1,000 km altitude for a period shortly after midnight. The data used in that paper were based on measurements of maximum inflexion Doppler slopes of simultaneous signals using high elevation orbits of the multiple-frequency navigational satellite 1961 Omicron I. Great care was taken to include in the statistics only those orbits for which the propagation paths of the various involved frequencies were nearly identical, that is, close to the overhead position. This reduces the available results considerably but increases the confidence in the correctness of the evaluation which assumes identical straight-line propagation. It could be seen that the diurnal contour of the content had some oscillations which need not indicate the presence of actual diurnal behaviour. Since the variation is based on two months of results the contour could include seasonal effects.