Investigating the Relative Role of NO Cooling and Solar Radiation on Thermospheric Temperature Changes During April 23, 2023 Geomagnetic Storm: GOLD Observations and GITM Simulations

Ionosphere-Thermosphere (IT) disturbances driven by geomagnetic storms have been extensively studied in previous works, but the thermospheric temperature variations remain poorly understood due to limited observations. The Global-scale Observations of the Limb and Disk (GOLD) mission provides an unprecedented opportunity to characterize these variations by offering continuous and high-cadence two-dimensional (2D) measurements of daytime thermospheric temperature. In this study, thermospheric temperature perturbations during the April 23, 2023 geomagnetic storm was investigated using GOLD observations. A noticeable cooling was observed during the recovery phase; that is, temperatures dropped below pre-storm levels. This decline may result from the overcooling effect of thermospheric nitric oxide (NO), or the reduced solar extreme ultraviolet (EUV) radiation during the recovery phase. To characterize and distinguish these effects, Global Ionosphere-Thermosphere Model (GITM) simulations with AMIE for the high latitude forcing were conducted, including a standard run and a controlled run in which storm-time solar radiation remained constant at pre-storm levels. By comparing GOLD observations with the standard and controlled GITM simulations, the relative contributions of NO cooling and solar radiation to the post-storm thermospheric cooling were examined. This study provides new insights into the thermospheric energy balance during storm recovery phases, with important implications for space weather modeling and upper atmospheric dynamics.