Response of Neutral Temperature in the Lower Thermosphere to Geomagnetic Storms Observed by ICON/MIGHTI

This study utilizes ICON/MIGHTI observations and reveals, for the first time, the response of neutral temperature in the lower thermosphere (∼110–130 km) to minor-to-moderate geomagnetic disturbances. A case study of the 12 October 2021 storm reveals surprising storm-time temperature enhancements across all observed latitudes (∼14°–42°N), with a peak enhancement of 28% at 130 km near 42°N. The average enhancement within 35°–40°N reaches 18% at 130 km. Statistical analysis indicates a positive correlation between temperature enhancement and geomagnetic activity intensity. The increase rates with respect to ap index are larger in 35°–40°N than those in 20°–25°N. The increase rates increase with altitude, reaching 0.168%/nT at 130 km over 35°–40°N. The peaks of temperature enhancements lag the ap/Dst index maxima/minima for most storms. Comparisons with the NRLMSIS2.1 empirical model and the physics-based TIEGCM-ICON model show that both models capture storm-time temperature enhancements but underestimate their magnitudes compared to observations.