Dynamics of Thermospheric Traveling Atmospheric Disturbance During a Geomagnetic Storm.

Traveling atmospheric disturbance (TAD) plays an important role in the energy and momentum transfer from the lower atmosphere to the upper atmosphere, and from high‐ to low‐latitudes. It is common to observe TADs propagating toward low latitudes because of enhanced Joule heating and/or the Lorentz force at the high‐latitude ionosphere during storm time. However, energy or momentum variation associated with their equatorward propagation remains unclear. Two geomagnetic storms occurred on 7–8 September 2017 and upper atmospheric disturbances are observed by the Swarm satellites and the Global Navigation Satellite System Total Electron Content network. We conduct a model simulation and term analysis of the energy equation to investigate the dominant terms of TAD. Adiabatic heating, conduction heating, and advection heating dominate the energy budget of TAD. Adiabatic heating plays an important role in the energy budget by transferring the most energy of TAD. An anti‐phase relationship between adiabatic and conduction heating is found in the propagation of these TADs. An in‐phase relationship between adiabatic and advection heating is also found. Physical processes behind these anti‐phase and in‐phase relationships are illustrated with a schematic. Finally, based on the dominant terms and the relationships between them, the whole process of generation, propagation, and dissipation of TAD is given. Plain Language Summary: Wave is a prevalent phenomenon in the atmosphere. They can transfer the energy and momentum from where they are generated to where they arrived. Traveling atmospheric disturbance (TAD) accompanied by gas expansion and compression is a specific wave type in the atmosphere. TAD often has a huge spatial scale of hundreds or even thousands of km, and it can propagate from one hemisphere to another hemisphere or even travel an entire circle around the earth. Many observations about TAD rise a challenge in explaining the mechanism of TAD's generation, propagation, and dissipation. This paper uses a physically based model to study TADs. We use the parameters calculated by the energy equation of the model to study the relatively effective heating processes in the energy budget of TAD. The relatively effective processes are found and relationships between them are shown. Further analysis and explanations are given to understand the relationships between these physical processes. Finally, the whole process from the generation of TAD to the dissipation of TAD is given. Key Points: Model‐data comparisons are used to understand the behavior of traveling atmospheric disturbance (TAD) during a geomagnetic storm on 7–8 September 2017A continental‐scale TAD/traveling ionospheric disturbance pair is observed simultaneouslyThe roles the dominant terms played during the propagation of TAD are given [ABSTRACT FROM AUTHOR]