Abstract Nitric oxide (NO), a minor constituent of the Earth's lower thermosphere, emits 5.3‐μm infrared radiation, causing an important cooling effect on the thermosphere. In this study, the eclipse‐induced NO cooling changes are investigated using the SABER and GOLD measurements and the Thermosphere‐Ionosphere modeling of the 14 October 2023 eclipse. The observations show a NO cooling depletion (∼4 erg/cm 3 /s, ∼40%) in SABER measurements that is concurrent with a reduction in neutral temperature (∼60 K) in GOLD observations around 150 km altitude, associated with an increased O/N2 ratio. The Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) captures the morphology of the eclipse‐induced effects but underestimates the observed variations. The data‐model comparison confirms this depletion caused by the decreased NO density and temperature. Model term analysis shows that the eclipse‐induced decrease in NO density is mainly produced by the chemical process instead of dynamic transport. The temperature‐dependent reaction rate of NO production from Duff et al. (2003, https://doi.org/10.1029/2002GL016720 ) was further tested and quantified the cooling depletion better. However, there still exists a discrepancy in neutral temperature changes. This study presents multi‐source observations of eclipse‐induced NO cooling changes, and contributes to the understanding of cooling processes in the thermosphere‐ionosphere system.
He et al. (2026) studied this question.