Large-scale irregularities in the high-latitude F region ionosphere represented by a numerical model, and comparison with Swarm observations

Abstract

A regional numerical model yields a three‑dimensional electron density distribution in the high‑latitude F region in the range of 150‑600 km. The model takes into account several processes, primarily the plasma convection and auroral particle precipitation, which are crucial for the polar ionosphere. A limited comparison of plasma densities reproduced by the model and obtained from Swarm satellite observations during periods of different IMF orientation is performed. Large‑scale ionospheric irregularities such as the tongue of ionization and the polar hole, both caused by specific convection patterns, are observed and modeled with sufficient accuracy. When the IMF Bz is positive, a cavity with reduced plasma density is formed in the central polar cap. A tongue of increased ionization extends from the day to the night side across the polar cap, but shifts toward dawn or dusk depending on the sign of the IMF By component and, as a consequence, the predominance of a particular convection vortex. Although the polar ionosphere is highly variable and considered poorly modeled, for individual events the physics‑based model shows reasonable agreement with  satellite observations. Results of numerical models can complement and extend the understanding of the high‑latitude ionosphere, the morphology of which is simplified in empirical models.