The Impact of Line-of-Sight Geometry on GNSS TEC Observations of Traveling Ionospheric Disturbances

The characteristics of traveling ionospheric disturbances (TIDs) inferred from observations of total electron content (TEC) are impacted by the geometry of line-of-sights (LOS) between Global Navigation Satellite System (GNSS) satellites and ground-based receivers piercing electron density fluctuations (e.g., Inchin et al., 2021). The choice of satellite-station pairs and their LOS orientations may favor or preclude the detection of TIDs and their following characterization and interpretation.
In this study, we focus on observing TIDs induced by acoustic and gravity waves (AGWs) generated by thunderstorms over the continental US, which benefits from the dense coverage of GNSS receivers. Events that have first been clearly identified using conventional TEC processing are selected for a more detailed examination. The TID characteristics are analyzed to estimate the associated period, horizontal wavelength, horizontal velocity, and amplitude, which are key physical parameters that provide an insight into the momentum and energy deposited in the ionosphere-thermosphere system by convectively-generated AGWs. Furthermore, the effect of magnetic-field line alignments of plasma drifts driven by AGWs at the bottom of the F region of the ionosphere, and the selection of specific LOSs that can favor the observations of these drifts are investigated. Resulting TEC maps are compared with the maps produced by our earlier-developed System for Rapid Analysis of Ionospheric Dynamics based on GNSS TEC Signals (10.17632/jbx98yscmd.1), and differences between the resolved TIDs are noted. The newly developed algorithms demonstrate an advancement in the accurate mapping and visualization of TIDs, and highlights the caveats and limitations one may face while analyzing TIDs based on TEC observations.