This study uses multiple ground and satellite-based measurements to investigate the extreme ionospheric response to the Mother's Day storm on May 10–11, 2024. Prompt penetration electric field caused a significant enhancement in the ionospheric vertical drift (∼ 95 m/s) and the equatorial electrojet strength (∼ 275 nT) over Jicamarca. These extreme eastward electric field perturbations, along with the large meridional wind, significantly altered the F-region plasma fountain at different local times. The afternoon equatorial ionization anomaly (EIA) not only sustained for an exceptionally long duration (∼12 hr) but also expanded spatially over time. The separation between the two peaks of EIA crests exceeded ∼48° and ∼70° in the morning and evening sectors, respectively. This study shows, for the first time, that unusually strong EIA can not only develop at different local t...

On 7 January 2005 (Ap=40) prompt penetration electric field perturbations of opposite polarities were observed over Thumba and Jicamarca on a few occasions during 13:45–16:30 UT. However, the electric field was found to be eastward during 14:45–15:30 UT over both Thumba and Jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points. On closer scrutiny, three important observational features are noticed during 14:10–15:15 UT. First, during 14:10–14:45 UT, despite increasing southward interplanetary magnetic field (IMF) Bz condition, the already westward electric field over Thumba weakened (less westward) while the eastward electric field over Jicamarca intensified (more eastward). Second, the electric field not only became anomalously eastward over Thumba but also got intensified further during 14:45–15:00 UT similar to Jica...