Observations of the F3-layer at equatorial region during 2005

The existence of the F3-layer has been observed at Brazilian equatorial stations. This paper reports on a 1-year observations at Parit Raja, Malaysia (Lat. 1°52′N, Long. 103°48′E). The greatest number of appearances of the F3-layer is around local noon while the least is after local dawn. Its occurrence is more pronounced during winter and the equinoxes. The mean height of reflection for the layer is about 600 km reaching a maximum of about 900 km during the winter of 2004/2005. It is seen that the critical frequency of the F2-layer decreases with the appearance of the F3-layer.