Large-Scale Disturbances in the Upper Thermosphere Induced by the 2022 Tonga Volcanic Eruption

The effects of volcanic eruptions on the ionosphere have been well studied, however, evidence for the anticipated upper atmospheric neutral variations and their exact extents of change are rarely available. Here, we report dramatic thermospheric disturbances following the 15 January 2022 Tonga eruption. The GRACE-FO and Swarm-C observations from the accelerometers exhibited three successive thermospheric density waves at ∼500 km altitudes propagating concentrically across the globe at 200-450 m/s phase speed and two of the three waves converged at the antipode of the epicenter. A large-scale and long-lasting neutral density depletion within a radius of approximately 10,000 km around the epicenter occurred, along with the density enhancement around the antipode of the epicenter. Such an enhancement is comparable in the relative intensity with respect to the no-eruption condition, to the effect of a moderate geomagnetic storm. This study offers observational evidence of substantial global upper thermospheric perturbations well above their origin near the Earth's surface due to a volcanic eruption.