Diurnal variations of the peak electron density distribution pattern at low latitudes derived from intercosmos-19 topside sounding data Original Research Article

From Intercosmos-19 topside sounding data convering all longitudes forf2 maps in the low-latitude ionosphere were constructed for quiet geomagnetic conditions in June and December solstices in solar maximum for different local time intervals, each lasting no more than 2 hours, by day and night, so that the changing pattern of the equatorial anomaly was obtained including the variations of both crests. Strong asymmetry between dynamics of the northern and southern crests was found. Comparison with the URSI peak maps reproduced in the International Reference Ionosphere IRI showed that the equatorial anomaly is stronger and persists for a longer time (on average until 04 LT) than in the model. The longitudinal structure of the peak electron density at low latitudes is shown in a set of maps. It is much more complicated than presented in the URSI/IRI model.