An Investigation on the Longitudinal Variation in Mid-Latitude Ionosphere Based on CHAMP Satellite Observations

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 degrees 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. Plain Language Summary Longitudinal variations of the mid-latitude ionosphere attract the interests of researchers, but the mechanisms are not fully addressed. In this work, the electron densities of in situ observations from the Challenging Minisatellite Payload satellite are used to investigate the longitudinal variations of the mid-latitude ionosphere climatically. These longitudinal variations are decomposed into spatial modes and temporal evolutions based on the principal component analysis method. We develop an empirical model to quantify the longitudinal structure at a specified condition. The most dominant variabilities in the mid-latitude ionosphere as a function of local times and seasons, associated with the hemisphere asymmetry, are well reproduced by the newly developed model. Our preliminary analysis indicates that the neutral winds dragging electrons along the geomagnetic field are the main driving source of the longitudinal evolution in the middle latitude ionosphere.

Automated summary

This study investigates the longitudinal variations of the middle latitude ionosphere using in situ electron density observations from the Planar Langmuir Probe onboard the Challenging Minisatellite Payload satellite. The results show significant seasonal and local time dependence of the longitudinal variation, which is different in the Northern and Southern Hemispheres. The analysis suggests that the interaction between the geomagnetic fields and the thermospheric winds drives the longitudinal variations in the ionosphere at middle latitudes.