Modeling the topside ionosphere by means of electron density values as recorded by the Swarm constellation

The topside part of the ionosphere lies above the ionospheric F2 layer peak and extends up to the plasmasphere. Since it contains a considerable part of the ionospheric plasma, its modeling is important for telecommunication’s purposes. In this work, electron density values recorded by Langmuir Probes on board the Swarm constellation are used as top anchor points by definite analytical functions (α-Chapman, β-Chapman, Epstein and Exponential) to investigate the variability of the topside plasma scale height H, a parameter which is crucial to perform a reliable modeling of the topside ionosphere. Bottom anchor points are provided by the IRIUP (International Reference Ionosphere UPdate) method, which is a method developed to update the IRI model relying on the assimilation of foF2 and M(3000)F2 data routinely recorded by a network of ionosonde stations. The IRIUP method calculates updated effective indices IG12eff and R12eff at each station of the network and, applying a universal Kriging method, generates maps of these indices which are then used to update the IRI output in terms of foF2 and hmF2. The height and electron density values of both top and bottom anchor points are used to obtain the H value, by means of a minimization procedure, making use of each of the aforementioned four topside analytical functions. The reliability of this approach is based on the hypothesis that H at heights around the F2 layer peak and for the first hundreds kilometers above is nearly constant, being this region dominated by O+ ions and with a temperature nearly constant. H values are statistically evaluated to look for any relevant relation with foF2 and hmF2. Moreover, a statistical comparison with COSMIC radio occulation profiles is carried out to asses which analytical profile function is the best one to represent the topside ionospheric profile, making use of the modelled H values.