Impact of different primary AGWs Generated by the 2022 Tonga Eruption on the Ionospheric Disturbances: Comparison of GITM-R simulations with GNSS observations

Volcanic eruptions provide broad spectral forcing to the atmosphere and can create disturbances in the ionosphere-thermosphere (IT) system by propagation of the associated acoustic and gravity waves (AGWs). These disturbances can be observed by Global Navigation Satellite Systems (GNSS) and used to analyze various properties of the initial perturbation such as localization and total energy content. The focus of this study is to simulate the ionospheric response induced by the 2022 Hunga Tonga-Hunga Ha’apai (HTHH) volcanic event using the Global Ionosphere-Thermosphere Model (GITM). GITM is driven by different AGW specifications to capture dominant portions of the broad spectral forcing. Simulation results from the High Altitude Mechanistic General Circulation Model (HIAMCM) are used to excite Traveling Ionospheric Disturbances (TIDs) related to secondary gravity waves and results from the Whole Atmosphere Community Climate Model with IT extension (WACCM-X) are used to excite TIDs generated by surface guided modes, such as Lamb and Perkins waves. GITMs response is compared to both the HIAMCM (-SAMI3) and WACCM-X outputs in the IT system as well as various Ionospheric data sets. Additionally, simulations are performed using GITM with local mesh refinement (GITM-R) near the source where acoustic waves are driven by a simplified source representation. The impact of the different forcing specifications is compared and discussed in the context of various IT data sets. It is found that, while the different primary forcing mechanisms are quite different in the thermosphere, they have similar Ionospheric TID responses in the near field. Additionally, strong acoustic forcing is shown to produce an ‘ionospheric hole’ that could play a role in the observed TEC response.