Diffusive equilibrium models for the height region above the F2 peak Original Research Article

The International Reference Ionosphere (IRI, see, e.g., Bilitza et al., 1993) does not take full advantage of (geo)physical relations in modelling the topside F region. This approach corresponds to the original IRI concept to provide a purely empirical model. Since O+H+ diffusive equilibrium is a very good approximation for the upper F region above about 600 km, we should make use of this geophysical relation to model the topside of the ionosphere. This was done for the “family” of “profiler” models developed at Graz and Trieste. Cost prof uses height aligned O+H+ diffusive equilibrium with 3 modeled parameters: the O+ plasma scale height at the F2 peak, its height gradient, and the O+H+ transition height. A peak is forced by using a Chapman layer formulation. NeUoG—plas uses a magnetic field aligned continuation of H+ diffusive equilibrium above a plasmasphere foot height of 2000 km. NeQuick applies the diffusive equilibrium concept in a simplified way by using an Epstein layer formulation, with a height dependence for the thickness parameter. The parameters that are used to calculate the topside in the three profilers are modeled from observed data.