The I-T Response to Most Recent Solar Eclipses: Observations and Modeling

We discuss multiple observations of atmospheric dynamics during recent solar eclipses: 21 August 2017, 4 December 2021, 20 April 2023, 14 October 2023, and 8 April 2024. We use GOLD and TIMED/GUVI instruments to observe the changes in the lower thermosphere related to atmospheric oxygen O, and molecular nitrogen N2. We discuss the problematic nature of O/N2 composition estimation from brightnesses under solar obscuration conditions, and how the observations should be properly interpreted. The Ionosphere-Thermosphere (I-T) system responds to solar X-Ray and Extreme Ultra Violet (EUV) radiation, which is highly non-uniform during solar eclipses. We introduce a new model of solar eclipse obscuration and irradiance by combining the solar occultation software PyEclipse and Flare Irradiance Solar Model 2 (FISM2) -- FISM2-Eclipse. We implemented FISM2-Eclipse into the Global Ionosphere thermosphere Model (GITM) and Whole Atmosphere Model Ionosphere-Plasmasphere-Electrodynamics model (WAM-IPE) to conduct a model-data comparison. We discuss some salient features noted during the recent eclipses.