# Effects of the October 2024 Storm over the Global Ionosphere
## 4 Results  
### Spatio-Temporal Variations in the Ionospheric Characteristics  
This section presents a global analysis of the ionospheric response to the geomagnetic storm that occurred on 10-11 October, with particular attention to Hemispheric asymmetries. The analysis focuses on two key ionospheric characteristics: foF2 and hmF2. To capture storm-time variations in these characteristics, we employed Ne profiles obtained from the COSMIC--2 RO satellite constellation. This constellation provides high-resolution coverage up to \(\pm\)45\({}^{\circ}\) geographic latitude, making it particularly suitable for examining ionospheric dynamics in equatorial and low- to midlatitude regions. 9 October, characterized by relatively quiet geomagnetic conditions, was selected as the reference day for comparison of ionospheric characteristics. Figures 3a-h and 4a-h illustrate the spatial and temporal evolution of foF2 and hmF2 over 9-11 October, in 3-h intervals. Each subfigure in Figures 3a-h and 4a-h represents data accumulated over a 3 h period, based on foF2 and hmF2 measurements derived from COSMIC--2 profiles. Prior to 15:00 UT on 10 October, ionospheric conditions remained largely consistent with the quiet-time reference. The SSC, recorded at 15:16 UT, marked the onset of the main phase of the geomagnetic storm (Figure 2). Between 15:00 and 18:00 UT, minimal ionospheric perturbations were observed in both Hemispheres. However, by 18:00-21:00 UT, storm-related signatures began to manifest. On the dayside of the Northern Hemisphere, particularly across the American sector, a significant increase in hmF2 was evident, indicating a substantial uplift of the F-region. Notably, foF2 values in this region remained largely unchanged. In contrast, on the nightside of the Southern Hemisphere--especially over eastern longitudes--foF2 exhibited a marked decrease, while hmF2 simultaneously increased, implying ionospheric uplift coupled with plasma depletion. An absence of foF2 and hmF2 data was observed in the Afro-European sector, highlighted by a red dotted box in Figures 3 and 4. This data gap began early in the storm and persisted through multiple phases. Figure 3: **(a-h)** Variation in foF2 (MHz) from COSMIC—2 RO during 9–11 October from (**a**) 00:00–03:00 UT, **(b)** 03:00–06:00 UT, **(c)** 06:00–09:00 UT, **(d)** 09:00–12:00 UT, **(e)** 12:00–15:00 UT, **(f)** 15:00–18:00 UT, **(g)** 18:00–21:00 UT, and **(h)** 21:00–24:00 UT. The yellow highlighted section represents the storm period (initial phase of the storm to SYM–H \(<-100\) nT during the recovery phase). The red rectangles in the subfigures represent the absence of foF2 values during the storm period. Figure 4: **(a-h)** Variation in hmF2 (km) from COSMIC—2 RO during 9–11 October from **(a)** 00:00–03:00 UT, **(b)** 03:00–06:00 UT, **(c)** 06:00–09:00 UT, **(d)** 09:00–12:00 UT, **(e)** 12:00–15:00 UT, **(f)** 15:00–18:00 UT, **(g)** 18:00–21:00 UT, and **(h)** 21:00–24:00 UT. The yellow highlighted section represents the storm period (initial phase of the storm to SYM–H \(<-100\) nT during the recovery phase). The red rectangles in the subfigures represent the absence of hmF2 values during the storm period. During the 21:00-24:00 UT interval, foF2 remained relatively stable on a global scale, but hnr2 continued to rise across both Hemispheres' dayside sectors, with uplifts reaching 150-200 km. Between 00:00 and 03:00 UT, coinciding with the SYM-H minimum, foF2 decreased significantly over the Southern Hemisphere nighttime sector. Simultaneously, a significant reduction in hnr2 was recorded over the isolated Australian longitudes (marked as \"A\" in Figure 4). Although storm activity weakened during the subsequent recovery phase, ionospheric disturbances remained pronounced in the Southern Hemisphere until approximately 12:00 UT. Isolated regions, marked as \"B\" and \"C\" in Figure 4, also showed severely low hnr2 values during this period.