Response of the F-region ionosphere to variations in the polar stratospheric vortex

Space weather variability driven by lower and middle atmosphere dynamics has been studied for some time, including the effects of Sudden Stratospheric Warmings (SSW), a temporary break-up of the polar vortex in the stratosphere. However, SSW events are relatively rare, making it challenging to understand the imposed ionospheric variations statistically. In contrast, the strength of the stratospheric polar vortex for which the Northern Annual Mode (NAM) index is being used as a proxy, can help us to better understand and predict lower atmospheric impacts on the F-region ionosphere from a statistical perspective as the NAM can be predicted a few weeks in advance. In this paper, the tidal spectra of F-region ionosphere electron density obtained from hourly COSMIC-2 Global Ionospheric Specification (GIS) data assimilation are correlated with the NAM index. Previous work focused on the migrating semidiurnal tide showed a strong anti-correlation with the NAM index, consistent with a stronger E-region wind dynamo during disturbed vortex conditions. We now extend these initial results to nonmigrating semidiurnal tides and diurnal tides, with emphasis on the winter months of the years 2020-2023.