Low-Latitude Ionospheric Disturbances Over Two Sectors of South America During 10–11 October 2024 Super Geomagnetic Storm

We analysed ground-based measurements (GPS-TEC, ionosondes, and magnetometers) combined with space-based observations (SWARM and GUVI) to investigate equatorial electrodynamics and low-latitude plasma distribution over the South American region during the 10–11 October 2024 geomagnetic storm (Sym-H ~ –350 nT). During the main phase (10 October, 16:12 UT–11 October, 01:45 UT), the equatorial electrojet (EEJ) over the Brazil/east (55°W) and Peru/west (75°W) sectors intensified by ~350 and 300 nT, respectively, and persisted for ~1.5 hours. This indicates strong prompt-penetration electric field perturbations. The enhanced eastward electric field produced a daytime super plasma fountain across both sectors. During the recovery phase, totla electron content (TEC) along the eastern sector showed markedly stronger depletion compared to western sector, associated with counter-electrojets and a reduced O/N₂ ratio in the east region. The EIA crests in the eastern sector remained depleted for about 8 hours, corroborating with in-situ electron density measurements from SWARM. In addition, Ionosonde observations from Araguatins (dip latitude: 6.2°S), Jataí (14.7°S), and São José dos Campos (22.2°S) revealed that the F layer rose from the evening hours on 10 October and remained elevated until 09:00 UT/06:00 LT on 11 October across all three stations. Spread-F over Araguatins developed at ~23:00 UT on 10 October and persisted until ~09:30 UT on 11 October. The 10-hour duration of Spread-F was facilitated by the continuous uplift of the F region throughout the night