From Bow Waves to Traveling Atmospheric Disturbances: Thermospheric Perturbations Along Solar Eclipse Trajectory

In this study, we investigate the characteristics of thermospheric perturbations triggered by a set of four solar eclipses, using the Thermosphere Ionosphere Electrodynamics General Circulation Model. Simulations show that temperature and horizontal wind perturbations have different wave rears but similar wavefronts, due to the coupling of energetic and dynamic processes. The perturbations are closely related to the eclipse trajectory, and their phase speed is modulated by the eclipse speed. As the eclipse shadow sweeps through the upper atmosphere, traveling atmospheric disturbances (TADs) are launched in the eclipse region and they, moving along with their moon shadow source, form bow wavefronts of thermospheric disturbances. The perturbations at a particular time are superimposed by preexisting waves and newly excited waves. With the termination of the eclipse near the sunset terminator, individual sequences are not any more organized along a specific alignment to form a bow wave. Instead, they evolve into freely propagating large-scale TADs. The large-scale TADs remain propagating in the direction perpendicular to the wavefronts, which is determined by history of the eclipse trajectory and thermospheric conditions. These conditions include specifically season and the latitudinal location of the eclipse trajectory.