Comparing the IRI model at high latitudes with long-term incoherent scatter radar data

The EISCAT Incoherent Scatter Radar systems situated in Svalbard (ESR) and on the Fenno-Scandinavian mainland have been operational for several decades. This allows the possibility to study the ionospheric plasma parameters over an extended solar cycle in the polar cap and several solar cycles in the auroral zone. Information is obtained on the electron density, electron and ion temperature and line-of-sight plasma velocity from an altitude of about 50 and up to ∼1600 kilometers. The accumulated long-term database is useful to evaluate ionospheric models such as the International Reference Ionosphere (IRI) model. We have compared the electron density data from the ESR with the predicted electron density from the IRI model. Our results show that the IRI model in general fits the ESR data well around the F-region peak. However, the model seems to underestimate the electron density at higher altitudes, particularly during the extended solar minimum. The study is extended to include results using the data from the EISCAT UHF radar situated in the auroral zone. The comparison between EISCAT data and the IRI model serves two important purposes: to validate the IRI model at high latitudes and to improve the IRI model by assimilation of the EISCAT data set.