Multi-Instrument Analysis of an MSTID Event over Northeastern Brazil: Insights into Atmosphere–Ionosphere Coupling

This study investigates a Medium-Scale Traveling Ionospheric Disturbance (MSTID) observed over Northeastern Brazil on December 28, 2019. A multi-instrument approach incorporating GNSS receivers, ionosondes, and Swarm satellite data was used to estimate the wave's horizontal speed of about 280 m/s and a wavelength of approximately 700 km. Analysis of HWM14 wind profiles and geomagnetic indices indicates that the event was not driven by local plasma instabilities or solar activity. Instead, the disturbance is associated with deep tropospheric convection identified in GOES-16 infrared imagery. These results suggest that gravity waves generated in the lower atmosphere propagated upward and modulated the ionosphere. The observations highlight the role of atmosphere–ionosphere coupling, where lower atmospheric processes influence ionospheric dynamics. The integration of multiple observational platforms provides strong evidence supporting the atmospheric origin of the MSTID.