Statistical study of the F3 layer characteristics retrieved from Intercosmos-19 satellite data

Abstract

This paper presents a statistical study of the equatorial F3 layer characteristics for the 1979–1981 period of high solar activity using the Intercosmos-19 (IK-19) topside sounding large data set (about 3600 passes across the equator). We revealed diurnal, seasonal, latitudinal and longitudinal variations in the F3 layer occurrence probability (P), and diurnal variations in maximum height of the F3 layer (hmF3). Three local peaks in P appear in diurnal variations for all seasons at: (1) 12:00–14:00 LT; (2) 17:00–18:00 LT; (3) 20:00–22:00 LT. The occurrence of these peaks is associated with diurnal variations in electromagnetic vertical plasma drift at the vicinity of geomagnetic equator. The F3 layer height increases from ∼450km in the early morning hours to 600–750km in the afternoon and reaches the maximum height of ∼800km at 21:00 LT. The latitudinal distribution of F3 layer has a maximum at the geomagnetic equator and it is approximately symmetric with respect to the geomagnetic equator regardless of the season. The F3 layer occurs most frequently in winter (45%), less frequently in summer (43%) and least frequently (37%) in the equinoxes. The F3 layer occurs more often in spring than in autumn. The longitudinal variation in P depends on longitudinal structure of equatorial ionization anomaly that principally determined by the variation in vertical plasma drift at the geomagnetic equator.