Features of the F3 layer occurrence over the equatorial location of Trivandrum

Abstract. The general features of the F3 layer occurrence over the magnetic equatorial location of Trivandrum (8.5° N; 77° E; dip lat ~0.5° N) in India during the period from 1996–2005 are presented using the ionosonde observations. The study brings out that the F3 layer occurrence over Trivandrum is weak and rare compared to the other equatorial locations. The F3 layer occurrence is relatively more pronounced during the magnetically active conditions, thus indicating the dependence of the layer formation over Trivandrum on magnetic activity. It is also observed that the percentage occurrence of the F3 layer decreases with increasing solar activity.