The effect of geomagnetic activity on the F₂ region over Central Africa

Abstract

This article describes the variations of ƒ_oF₂ at stations in central Africa, where the geomagnetic and magnetic equators are greatly separated from each other. At Lwiro and Léopoldville (geomagnetic latitude Φ=3-4°S, magnetic latitude μ=16-18°S), the diurnal variations of ƒ_oF₂ show a single and strong maximum in the afternoon hours. The seasonal variation of noon h'F₂ at these stations has one single maximum during local summer. An increase of magnetic activity causes a decrease of the daytime values of ƒ_oF₂ during local summer months, but it increases the same during local winter months. The storm-time variations of ƒ_oF₂ at these stations show a short initial increase with the start of the magnetic storm followed by a large decrease on the second day of the storm. These properties of ƒ_oF₂ are very similar to those observed at temperate latitude stations. The variations of ƒ_oF₂ at Djibouti (Φ =: 7°N, μ=3°N) and Ibadan (Φ=11°N, μ=3°S) are very different from those at Lwiro or Léopoldville and are of the equatorial type. It is concluded that the variations of ƒ_oF₂ at low and medium latitudes are determined by the magnetic and not by the geomagnetic latitude of the station.