Equatorial spread-F at Ibadan, Nigeria

Abstract

The characteristics of equatorial spread-F at Ibadan (magnetic latitude 3°S) are investigated including nocturnal, seasonal, solar-cycle and magnetic disturbance variations; and all of these are found to show marked correlations with corresponding changes in the height of the layer. For example spreading begins shortly after the evening rise in the layer, and becomes less intense and more restricted to the higher frequencies as the layer descends later in the night. Also at Ibadan spread-F incidence on quiet days is found to increase with solar activity; and this corresponds to a marked increase in the evening rise of the layer as the solar cycle advances. A possible interpretation of these and earlier results is that the irregularities responsible for spread-F are due to hydro-magnetic disturbances which are increasingly attenuated at lower heights