Investigation of the ion composition in the topside ionosphere at solar maximum using incoherent scatter technique

Abstract

The aim of this study was to investigate the altitudinal and diurnal variations of light ion densities in the topside ionosphere during the 23rd and 24th solar maximums. This made it possible to understand the behavior of the ion composition after extended solar minimum and compare how it differs from the preceding solar maximum. The observed variations are compared with estimates of empirical (IRI) and physical (SAMI3) models. All necessary data were obtained at Kharkiv Ionospheric Observatory for the summer solstices during the 23rd and 24th solar cycles. The observations showed that there are more helium than hydrogen ions in the daytime during the 23rd solar maximum compared to 24th. The relative concentration of H+ decreases with increasing of solar activity. The O+ have an opposite behavior to H+ and He+ ions: at increasing solar activity, the O+ concentration increases. The dynamic processes have an effect on the variations of light ions in the upper ionosphere. It is found that variations in the mixing ratio of the three main topside ion species above Ukraine differ both qualitatively and quantitatively from the model variations. The experimental relative concentrations of H+ and He+ were much higher than empirical and physical model estimates. There is a somewhat better agreement in the case of O+ densities. The results obtained in this work can be useful in predicting of variations the relative concentration of H+, He+ and O+ in the upper ionosphere over the Central Europe region.