Investigation of Gravity Wave-Driven Ionospheric Variability Using High Resolution WACCM-X

Atmospheric gravity waves (AGWs) are key drivers of vertical coupling between the lower atmosphere and the Ionosphere-Thermosphere (IT) system. Generated primarily by tropospheric weather systems, these waves propagate upward and exponentially grow in amplitude as density decreases. At ionospheric altitudes, these waves modulate neutral winds and induce plasma modulations via ion-neutral collisions. One of the major manifestations of the AGW signatures in the F-region ionosphere is the Medium-Scale Travelling Ionospheric Disturbances (MSTIDs). In our recent coordinated observations from the NASA Atmospheric Waves Experiment (AWE) and GNSS TEC measurements, we observed strong mesospheric -ionospheric coupling over CONUS (Girijakumary and Lu, 2026, under review). To further investigate the vertical transmission globally, we utilize the Whole Atmosphere Community Climate Model, WACCM-X High-Resolution Nature Run. This global atmosphere model extends from the surface to the thermosphere, with a horizontal resolution of 25 km and a vertical spacing of ~ 0.1 scale height, enabling better representation of mesoscale AGWs and their vertical propagation. GW activity is characterized by the perturbations in horizontal and vertical winds after removing the large-scale background. Perturbations with horizontal wavelengths of approximately 200-1000 km corresponding to medium-scale GWs are isolated by applying 2D-FFT band pass filtering. Density-weighted kinetic energy, derived from the wind perturbation fields, is used as a proxy for GW activity at the stratospheric and mesospheric altitudes. Similarly, band-pass-filtered perturbations in the electron density near 300 km are used to quantify ionospheric variability. Plasma perturbations with the same horizontal wavelengths are retained to isolate MSTID scales. By comparing the GW activity at multiple altitudes in the MLT region and plasma fluctuations at 300 km, this study examines the vertical propagation pattern and its role in generating MSTIDs. In addition, the one-year simulation is used to assess seasonal trends and examine how background winds, vertical shear, and various electrodynamic factors affect vertical coupling.