Ionospheric variability over Jicamarca during the recent extreme space weather event

This study analyzed measurements from the Jicamarca Radio Observatory (JRO; 11.9°S, 76.8°W, magnetic dip 1°N) to investigate the ionospheric response to recent extreme space weather events during Solar Cycle 25. Specifically, we utilized Jicamarca radar observations to examine the behavior of equatorial ionospheric electrodynamics and spread F irregularities. Additionally, we incorporated data from the Digisonde to analyze ionospheric virtual height (h’F) and equatorial spread F (ESF), measurements from the Advanced Composition Explorer (ACE) satellite to assess solar wind conditions, and geomagnetic field observations from SuperMAG to evaluate geomagnetic variations. Furthermore, we used data from the Swarm satellite constellation and GPS-derived total electron content (TEC) measurements to study electron density and ionospheric irregularities. During the main phase of the geomagnetic storm, a strong eastward prompt penetration electric field led to sustained enhancements (lasting more than one hour) in the E×B vertical plasma drift, the equatorial electrojet (EEJ), and the F-layer ionospheric height during the afternoon hours. The increase in E×B vertical plasma drift resulted in a significant intensification and latitudinal expansion of the equatorial ionization anomaly (EIA) on both sides of the magnetic equator. During the prereversal enhancement (PRE) period, the combined effects of the eastward penetration electric field and the background zonal electric field significantly increased the upward E×B vertical plasma drift, reaching velocities of up to 98 m/s. This enhancement facilitated the development of plasma bubbles, which ascended to higher altitudes (~950–1500 km) over Jicamarca, as recorded by incoherent scatter radar. Simultaneously, Swarm satellite observations captured the expansion of ionospheric irregularities to higher latitudes. During the recovery phase of the geomagnetic storm, the eastward disturbance dynamo electric field sustained an increase in the vertical plasma drift and the F-layer ionospheric height.