Ionospheric Disturbances generated by the 2015 Calbuco Eruption: 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 developed acoustic-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 [1], wavelength [2], and total energy content [3]. The focus of this study is to simulate ionospheric Total Electron Content (TEC) variations induced by the first phase of the 2015 Calbuco volcanic eruption using a global circulation model and to subsequently compare the simulated results to GNSS data. Simulations using the Global Ionosphere-Thermosphere Model with local mesh refinement (GITM-R) are performed to capture mesoscale AGWs in the regions near the volcano [4]. Because GITM’s lower boundary is at ~100 km altitude, a spectral AGW propagation model is used in conjunction with a volcanic source model to specify the perturbation at GITM’s lower boundary. Two different specifications on the propagation model are applied, (1) direct propagation [5] and (2) ground-coupled propagation [6]. The simulated TEC variations for both specifications are compared to GNSS data to demonstrate GITM’s ability to resolve mesoscale acoustic-gravity wave signals induced by volcanic eruptions and examine the impact of considering ground-coupled airwaves on the simulated TEC variations.