Analysis of Tonga eruption-induced disturbances in the upper thermosphere based on atmospheric drag accelerations from LEO satellites

Abstract

Abstract The violent eruption of the Tonga volcano on 15 January 2022 triggered significant disturbances in the atmosphere and ionosphere. However, limited observational capabilities have persistently hindered the characterization of eruption-induced neutral density disturbances in the upper thermosphere. In this study, the atmospheric drag accelerations of five low Earth orbit (LEO) satellites operating at altitudes at ~ 430 km and ~ 500 km, including SWARM-A/B/C and GRACE-C/D, are derived from reduced-dynamic precise orbit determination. Based on these data, possible anomalous perturbations associated with the Tonga eruption are identified, and their propagation characteristics are further analyzed. Following the eruption, between 08:00 and 16:00 UT, a large-scale density depletion centered around Tonga with a radius of approximately 10,000 km is observed, nearly covering the regions of Australia and the Pacific Ocean. In addition, a significant density enhancement is detected to the west of the antipode. Analysis results indicate that these large-scale disturbances in atmospheric drag (AD) acceleration are more likely caused by the propagation of gravity waves (GWs), with vertical speeds $$\:{c}_{V}\cong\:$$ 40.3–67.6 m/s, horizontal speeds $$\:{c}_{H}\cong\:$$ 613.9–677.1 m/s at ~ 500 km height and $$\:{c}_{H}\cong\:$$ 568.0–593.9 m/s at ~ 430 km height. Moreover, a comparison of AD acceleration variations from SWARM-A and SWARM-B suggests that neutral density disturbances caused by GWs may take longer to dissipate at higher altitudes. However, a definitive explanation for this phenomenon remains unclear at present. This study demonstrates the feasibility of using LEO satellites as mobile “cameras” to detect natural hazards-induced neutral density disturbances at their orbital altitudes. Additionally, the dynamic orbits and limited availability of LEO satellites make it difficult to capture large-scale, simultaneous observations of neutral density. Nevertheless, with the ongoing development of LEO satellite constellations, such capability is promising and highly anticipated.