Comparison of ion densities measured in the topside ionosphere at low latitudes and midlatitudes with calculations of ionospheric models over a full solar cycle

Measurements of total ion density at 840 km altitude at all latitudes in four local time sectors are available from 1987 to the present from spacecraft of the Defense Meteorological Satellite Program (DMSP). Thus all phases of the past solar cycle are represented in the data set. We present comparisons of the measurements with values obtained from climatology models of the ionosphere. The models examined are the International Reference Ionosphere (IRT) model, the Parameterized Ionospheric Model (PIM) and the Reilley - ICED Bent - Gallagher (RIBG) model. We show that all of the models reproduce some of the features of the observed topside ionosphere, but none of the models match all of the observations.