Atmospheric Tidal Variability and Gravity Wave Forcing During the January 19–21, 2026 Geomagnetic Storm

Abstract. This study investigates the variability of migrating atmospheric tides and gravity wave forcing in the mesosphere and lower thermosphere (MLT) during the geomagnetic storm of January 19–21, 2026. Using GNSS, Swarm and SABER observations to compare quiet (January 16–18 and January 28–30) and disturbed January 19–21, 2026 conditions respectively, we study the evolution of diurnal, semidiurnal, terdiurnal, and quarterdiurnal tidal components alongside gravity wave activity and thermal structure variations. Results reveal a 21 % storm-time amplification of semidiurnal and terdiurnal tides, accompanied by phase shifts at 20° North, 20° South and the emergence of non-migrating tidal components. Gravity waves exhibit enhanced amplitudes by 43 %, increased intermittency, and reduced vertical coherence, indicating strong wave mean ow interactions and localized dissipation. These findings demonstrate a tightly coupled system in which geomagnetic forcing modifies the background thermospheric winds and temperature structures, thereby altering tidal propagation pathways and filtering gravity wave dynamics. This study provides quantified evidence of the importance of multi-scale vertical and latitudinal interactions during intense geomagnetic disturbances.