Charles Owolabi

The longitudinal variations of the middle latitude ionosphere are investigated on the basis of in situ electron density observations from the Planar Langmuir Probe onboard the Challenging Minisatellite Payload satellite. This study specifically focused on the longitudinal variations of the ionosphere at geographic latitudes of 40° in both the Northern and Southern Hemispheres. The longitudinal variations of the ionosphere are decomposed into the spatial modes and corresponding temporal evolutions by employing the principal component analysis method, and an associated empirical model is developed. The model results indicate a significant seasonal and local time dependence of the longitudinal variation, which is obviously different in the Northern and Southern Hemispheres. Our preliminary analysis suggests that the interaction between the geomagnetic fields and the thermospheric winds results in the longitudinal variations in the ionosphere at the middle latitudes. In addition, the relative contributions of zonal and meridional winds are further discussed.