[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-16] Evaluating the generation of traveling ionospheric disturbances by solar terminators and eclipses

★Invited Papers

*Hyosub Kil^1,2 (1.Korea Astronomy and Space Science Institute、2.Johns Hopkins University Applied Physics Laboratory)

キーワード：Earth's ionosphere, traveling ionospheric disturbance, solar eclipse

Solar terminators and eclipses are suspected sources of traveling ionospheric disturbances (TIDs). Atmospheric waves generated by pressure gradient forces during transitions between darkness and sunlight can give rise to TIDs. The coincident occurrence of ionospheric disturbances with terminators and eclipses, along with their propagation at the same speed, has been suggested as observational evidence of TIDs and their connection to these phenomena. We evaluate this hypothesis using total electron content (TEC) data over the United States from the ground-based Global Navigation Satellite System (GNSS). Detrended TEC data from the solar eclipses of August 2017 and April 2024 reveal two distinguishing features: (1) TEC depletions along the eclipse paths and (2) westward-moving TEC depletions along the sunrise terminator. These features can be interpreted as large-scale TIDs. However, rapid changes in ionospheric plasma density around sunrise and totality introduce substantial deviations between actual and detrended (filtered) TEC values. Since the characteristics of these deviations vary depending on the filtering methods used for detrending, the observed TEC perturbations—including large-scale TID-like features—around sunrise and eclipses may be false TID alarms. To further support the presence of false TID alarms around sunrise, we present electron density irregularity distributions derived from satellite data and GNSS TEC.