Do Eclipse-Induced Thermospheric TADs Originate From Above or Below?

Solar eclipses generate significant wave activity in the Earth's upper atmosphere. The source region of eclipse-induced Traveling Atmospheric Disturbances (TADs) in the upper thermosphere—particularly the relative contributions of gravity waves from the thermosphere itself versus the lower atmosphere—remains unknown. Using the Whole Atmosphere Community Climate Model with thermosphere–ionosphere extension (WACCM-X), we investigate TADs triggered by the 26 December 2019 annular solar eclipse. Simulations demonstrate that eclipse-shadow passage launches thermospheric wave disturbances as TADs, with primary excitation occurring above 80 km altitude rather than in the lower atmosphere. These TADs propagate at speeds of ∼550 m/s, with trajectories dictated by the eclipse path. Thermospheric heating rates, temperature, and neutral wind analyses along propagation paths reveal that 80%–90% of the disturbance amplitudes originate in the upper atmosphere, while the lower atmosphere contributes 10%–20% of the disturbance amplitudes.