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The total solar eclipse of 21 August 2017 was simulated with the Global Ionosphere-Thermosphere Model (GITM), and the results were compared with the total electron content (TEC) measurements provided by the Global Navigation Satellite System, as well as F2 layer peak electron density (NmF2) derived from six ionosondes. TEC decreased over North America by similar to 54.3% in the model and similar to 57.6% in measurements, and NmF2 decreased by similar to 20-50% in the model and similar to 40-60% in the measurements. GITM predicted a posteclipse enhancement of similar to 10% in TEC and NmF2, consistent with observations which suggested an increase of similar to 10-25% in TEC and similar to 10-40% in NmF2. GITM showed that the divergence of horizontal winds drove the increase in Oxygen after the eclipse allowing an increase in the ionization rate. The slower charge exchange due to both the decreased ion temperature and N-2 density allowed an increase of O+ density in the F region also.

Plain Language Summary The total solar eclipse of 21 August 2017 was explored with the Global Ionosphere-Thermosphere Model, which simulates weather in space. The results were compared with ionospheric observations from the Global Navigation Satellite System and six ground-based measurements. Both the model and data showed a decrease in ionospheric densities during the eclipse and an enhancement above what would happen without the eclipse after the passage of the moon. The analysis showed that the posteclipse enhancement in the ionosphere was caused by the enhanced neutral Oxygen density, which was driven by the horizontal winds, as well as decreased neutral N-2 density, which was driven primarily by the cooling of the atmosphere.