Ionospheric Responses to an Extreme (G5‐Level) Geomagnetic Storm Using Multi‐Instrument Measurements at the Jicamarca Radio Observatory on 10–11 October 2024

Abstract On 9 October 2024, a fast‐moving coronal mass ejection erupted from the Sun and interacted with Earth on October 10 at around 1530 UT, causing a powerful G5‐class geomagnetic storm with a Sym‐H index of approximately −341 nT. During the storm's main phase, a strong eastward penetration electric field led to enhancement in Equatorial Electrojet (EEJ), 150 km echoes, E × B vertical plasma drift, and virtual F ‐region height ( h ′ F ) over the equator that sustained over 1.5 hr between 1530 and 1700 UT (1030–1200 LT), with maximum increases of 290 nT, 85 m/s, 60 m/s, and 280 km, respectively. The enhanced E × B vertical plasma drift caused a significant increase (50%–100%) and latitudinal extension (∼23–51°N and 18–57°S magnetic latitudes) of the equatorial ionization anomaly (EIA) on both sides of the magnetic equator. During the pre‐reversal enhancement hour at 00:00 UT (19:00 LT), the combined effects of eastward penetration and the background electric field strongly enhanced upward E × B vertical plasma drifts to 98 m/s causing plasma bubbles to reach higher altitudes (∼950–1500 km) over Jicamarca, as recorded by incoherent scatter radar. Ionospheric irregularities extended poleward, reaching up to 42°N and 43°S magnetic latitudes. The eastward disturbance dynamo electric field and disturbed thermospheric neutral winds caused the nighttime development of the EIA as well as the prolonged ionospheric rise at the magnetic equator. Continuous oscillations in the EEJ, 150 km echoes, E × B plasma drift, h ′ F , and ionospheric plasma density associated with disturbance polar currents are noticed.