On the Relationship Between Traveling Atmospheric Disturbances and Traveling Ionospheric Disturbances

Abstract

As the typical thermospheric/ionospheric wave, traveling atmospheric disturbances (TADs)/traveling ionospheric disturbances (TIDs) always carry and transfer a large amount of energy and momentum during geomagnetic storms. In this study, we conducted a model simulation to explore the relationship between TADs and TIDs. Our term analysis indicates that neutral wind transport plays an essential role in coupling TIDs with TADs. Meanwhile, ambipolar diffusion and photochemical processes act as dissipative mechanisms at relatively high and low altitudes, respectively. Further analysis along the tracks of TADs shows that the two manifestations of TIDs, the peak height and density of the F2 layer ($h_m{F}_2$ and $N_m{F}_2$) perturbations, are anti-correlated. This anticorrelation is driven by neutral wind transport caused by plasma density gradients near $h_m{F}_2$. When TIDs manifest as Total Electron Content (TEC) perturbations, neutral wind perturbations (TADs) modulate TIDs through photochemical processes by raising and lowering the ionosphere. Finally, we discuss how TADs modulate TIDs at different altitudes, latitudes, and hemispheres. We demonstrate that the hemispheric asymmetry of the O/N₂ ratio leads to a corresponding hemispheric asymmetry in TIDs. Our findings enhance the understanding of how the thermosphere and ionosphere are coupled through waves and how energy and momentum are exchanged in the thermosphere-ionosphere system via these waves.