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 ~54.3% in the model and ~57.6% in measurements, and NmF2 decreased by ~20–50% in the model and ~40–60% in the measurements. GITM predicted a posteclipse enhancement of ~10% in TEC and NmF2, consistent with observations which suggested an increase of ~10–25% in TEC and ~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 N2 density allowed an increase of O+ density in the F region also.
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