Dynamic of night-time equatorial F layer: Equinox transition at the magnetic equator in Africa

We study equatorial night-time F layer behaviour from quarter-hourly ionograms at Korhogo/Ivory Coast (9.2°N, 5°W, dip lat. -2.4°) during local Spring March-April 1995, declining solar flux period, according to the magnetic activity. The height and thickness of the F-layer are found to vary intensely with time and from one day to the next. At time of the equinox transition, by the end of March, a net change of the nightly height-time variation is observed. The regime of a single height peak phase before 22 March changes to up to three main F-layer height phases after 30 March, each associated to a dominant mechanism. After the 21 April magnetic-equinox period, the height-time morphology becomes more irregular suggesting meridional wind abatement.