Unusual Variation in Nitric Oxide Radiative Flux and Neutral Density Over Hunga-Tonga Region Caused by the Volcanic Eruption

Large-scale volcanic eruptions, such as the Hunga-Tonga volcanic eruption that occurred in 2022, can impact the atmospheric structure and dynamics in a highly complex way. The response of Nitric oxide (NO) radiative emissions to the lower atmospheric forcing caused by the Hunga-Tonga eruption has been examined in this study using Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) measurements. On 15 January, neutral densities and NOIRF (Nitric Oxide Infrared Radiative Flux) were found to be depleted over the Hunga-Tonga following the volcanic eruption, as observed by Swarm and SABER. Subsequently, the following day, a significant and highly localized enhancement in NOIRF is observed. Using TIEGCM (Thermosphere Ionosphere Electrodynamics General Circulation Model) simulations with gravity wave input, it has been established that wave-induced lower atmospheric forcing is primarily responsible for the compositional and temperature changes. These changes influence the vibrational excitation mechanism of NO, resulting in the observed emission pattern during the Hunga-Tonga event.