Ionospheric topside models compared with experimental electron density profiles

Recently an increasing number of topside electron density profiles has been made available to the scientific community
on the Internet. These data are important for ionospheric modeling purposes, since the experimental information
on the electron density above the ionosphere maximum of ionization is very scarce. The present work
compares NeQuick and IRI models with the topside electron density profiles available in the databases of the
ISIS2, IK19 and Cosmos 1809 satellites. Experimental electron content from the F2 peak up to satellite height
and electron densities at fixed heights above the peak have been compared under a wide range of different conditions.
The analysis performed points out the behavior of the models and the improvements needed to be assessed
to have a better reproduction of the experimental results. NeQuick topside is a modified Epstein layer,
with thickness parameter determined by an empirical relation. It appears that its performance is strongly affected
by this parameter, indicating the need for improvements of its formulation. IRI topside is based on Booker's
approach to consider two parts with constant height gradients. It appears that this formulation leads to an overestimation
of the electron density in the upper part of the profiles, and overestimation of TEC.