Some characteristic features of the equatorial ionosphere and the location of theF-region equator

The characteristic features of the equatorial F region are studied using the published ionospheric data. The study reveals some important differences in the Asian, African, and American zones. In the diurnal variation of foF2 there are two peaks, one in the forenoon and the other in the afternoon, in the Asian zone, whereas the afternoon peak is absent in the American zone during sunspot maximum. The width of the equatorial trough is smaller in the American than in the Asian zone. The location of the F-region equator is examined; the results indicate that the F-region equator does not correspond exactly to the magnetic dip equator but is shifted slightly toward the north in the Asian and American zones and slightly toward the south in the African zone.