# Effects of the October 2024 Storm over the Global Ionosphere
## 5 Discussion
(2025) [18] noted polar irregularities reaching \(\sim\)45\({}^{\circ}\) magnetic latitude and asymmetrical EPB behaviour over South America--confined to the equator in Sao Luis but extending to midlatitudes--mergingwith auroral structures. This likely caused a strong F-region uplift apparent on ionograms, as supported by [PERSON] et al. (2025) [PERSON] et al. (2025) and Figure 4. Strong F-region uplift was observed globally during both the storm's main and recovery phases (Figure 4a-h), with vertical drift speeds exceeding 100 m/s (Figure 8a). The most intense uplift occurred over Ascension Island, accompanied by enhanced hmF2 at other Southern Hemisphere stations. These effects are attributed to PPEFs driven by southward IMF--Bz and increased Eye electric field. PPEFs can reach the ionosphere at 5-10% of the upstream field strength [29]. As per [PERSON] (1969) [PERSON] (1969) [26], such electric fields result from the solar wind-polar cap interactions, producing eastward PPEFs and upward E \(\times\) B drift. Around 16:00 UT on October 10, IMF--Bz dropped from 6.8 nT to \(\sim\)--8.9 nT, sustaining the uplift. During recovery, a positive IMF--Bz-initiated DDEF gradually shifts ionospheric dynamics. As [PERSON] and [PERSON] (1980) [30] explained, auroral heating triggers equatorward wind, forming Hadley-like circulation and reversing quiet-time electric patterns. The combined effect of DDEFs and PPEFs explains the widespread F-region uplift during the October 2024 storm. Throughout 10-11 October, negative ionospheric storm effects were evident on the nightside of the Southern Hemisphere, whereas on the dayside, particularly during the storm's active and recovery stages, elevated F-trace heights occurred without a significant increase in foF2. This suggests ionospheric uplift without corresponding Ne enhancement at COSMIC--2 sampling altitudes. Interestingly, [PERSON] et al. (2025) [17] noted a slight foF2 increase over midlatitude Europe during the same storm, in contrast to COSMIC--2 data. This discrepancy may be due to G-conditions, as shown in Figures 5a-h-7a-h, where the F2 peak may have risen above COSMIC--2's range, leading to underdetection by satellite instruments but detection by ground-based ionosondes, as reported by [PERSON] et al. (2025) [17]. This underscores the need for combined satellite and ground-based observations for a comprehensive understanding of ionospheric storm dynamics. A clear poleward expansion of the EIA and the associated Hemispheric asymmetries in the ionospheric response to the October 2024 geomagnetic storm were observed. Swarm A in situ Ne measurements (Figures 10a-t and 11a-t) distinctly capture the EIA expansion during the initial and main phases of the storm. These observations are further supported by intensified eastward plasma drift recorded at Eglin and Ascension Island (Figure 8c), highlighting the significant role of electric field dynamics in modulating storm-time plasma transport. While the poleward expansion of the EIA during the October 2024 storm was previously noted by [PERSON] et al. (2025) [18], the present study offers a more comprehensive, global perspective using Swarm satellite data, capturing the evolution of the EIA across both Hemispheres and multiple longitude sectors. A key emphasis is placed on the Hemispheric asymmetry of the storm-time ionospheric response, which is attributed to variations in particle precipitation and thermospheric heating. These processes enhance ionization while simultaneously increasing recombination rates, ultimately leading to Ne depletion. This asymmetry is strongly influenced by the day--night variation in Hall conductivity, which modulates the electrodynamic response between Hemispheres. During severe geomagnetic storms, the electric field associated with the equatorial \"superfountain\" effect becomes substantially more intense than that under quiet conditions. As described by [PERSON] et al.