Generating electron density archives using mainland EISCAT data between 2001-2021 at 10 minute and 1 hour integration

The mesosphere/lower-thermosphere/ionosphere (MLTI) region is a critical boundary in the coupling of the atmosphere, climate and space weather, however it is one of the least understood regions, making it hard to include in whole atmosphere models. The EISCAT radars at Tromsø, Norway (UHF and VHF) have been measuring ionospheric parameters, such as electron density, since 1985 making it an excellent resource to study changes in the ionosphere over a long time period. This paper details how we have combined high elevation data from both radars between 2001-2021, re-integrated at 10 minutes and 1 hour, to look at the different sources of variability in the MLTI region between 50-200 km. Day of year climatology’s of the electron density highlight that the VHF data are more prone to contamination from Polar Mesospheric summer Echos. The magnetic local time variation of the electron density shows seasonal and altitude dependence related to solar UV illumination and electron precipitation, as expected. We compare our archives to the Empirical Canadian High Arctic Ionospheric Model (E-CHAIM) and find the biggest differences during the winter months and below 100 km, where the model does not yet include the impact of high energy electron precipitation.

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