Equatorial range spread F and high multiple echoes from the F region

Abstract

It has been shown that the post-sunset rise of the minimum virtual height (h'F) of theF region of the ionosphere near the magnetic equator during the high sunspot years is an effect of the overall rising of the completeF region. This feature of theF region produces very high order multiple reflections from theF regions. On some occasions strong spreadF is observed simultaneously with the high multiples suggesting theF region to be smooth and devoid of irregularities inside it. The irregularities causing the spreadF during the early stages of its development are suggested to be at heights below theF region.