Abstract
Abstract. Incoherent scatter radar measurements are an important source for studies of ionospheric plasma parameters. In this paper the EISCAT Svalbard radar (ESR) long-term database is used to evaluate the International Reference Ionosphere (IRI) model. The ESR started operations in 1996, and the accumulated database up to 2012 thus covers 16 years, giving an overview of the ionosphere in the polar cap and cusp during more than one solar cycle. Data from ESR can be used to obtain information about primary plasma parameters: electron density, electron and ion temperature, and line-of-sight plasma velocity from an altitude of about 50 and up to 1600 km. Monthly averages of electron density and temperature and ion temperature and composition are also provided by the IRI model from an altitude of 50 to 2000 km. We have compared electron density data obtained from the ESR with the predicted electron density from the IRI-2016 model. Our results show that the IRI model in general fits the ESR data well around the F2 peak height. However, the model seems to underestimate the electron density at lower altitudes, particularly during winter months. During solar minimum the model is also less accurate at higher altitudes. The purpose of this study is to validate the IRI model at polar latitudes.
Highlights
Electron density in the polar cap F-region ionosphere is produced by solar extreme ultraviolet radiation, transport of plasma density structures from lower latitudes and particle precipitation and is reduced by recombination and transport to lower latitudes
If the International Reference Ionosphere (IRI) model had been a perfect fit to the EISCAT Svalbard radar (ESR) data, all the data would have been located in the bar where the ratio is 1, as indicated by the red line
Electron density from the IRI-2016 model has been compared with data from the EISCAT Svalbard radar covering more than one solar cycle
Summary
Electron density in the polar cap F-region ionosphere is produced by solar extreme ultraviolet radiation, transport of plasma density structures from lower latitudes and particle precipitation and is reduced by recombination and transport to lower latitudes. Plasma density structures in the high-latitude F region are transported anti-sunward across the polar cap and sunward in the auroral zone due to electric convection (e.g., Cowley and Lockwood, 1992). This transport can increase the electron density in the nightside significantly when structures produced by solar extreme ultraviolet radiation in the sunlit ionosphere follow the convection lines into the polar cap. The patches are transported over the polar cap following the convection pattern
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