Analytical functions to describe the lower topside in the electron density profiles and comparisons with IK-19 data

We analyzed some 1-layer topside functions (namely Epstein, Chapman with alpha=0.5 and alpha=1.0 and NeQuick's topside) often used in electron density models of the Ionosphere, in comparison with experimental data of 7138 profiles provided by the InterKosmos 19 satellite onboard sounder. Regardless of the physical aspects and considering only the analytical ones (derivative, inflection point, scale parameter) we investigated the requirements for a suitable function in order to better model the lowest part of the topside, towards a possible improved version of the NeQuick's topside.