# Effects of the October 2024 Storm over the Global Ionosphere
## 4 Results
### Large-Scale Travelling Ionospheric Disturbances
From 22:00 to 00:00 UT, as the storm approached maximum intensity (Figure 16), dTEC maps revealed widespread LSTID activity throughout the Northern Hemisphere. Over Europe, LSTIDs propagated from northeast to southwest in the polar region and expanded toward midlatitude by 23:40 UT. Midlatitude LSTIDs moved northeastward until they were surpassed by polar-origin depletions. Japan registered LSTIDs moving from northeast to southwest, which weakened by 23:40 UT following the arrival of significant depletions. In North America, the LSTID signature was clearly observed with a northeast-to-southwest orientation across much of the region. At the peak of the storm, as the SYM--H index reached its minimum (~01:46 UT), LSTID activity was observed across all three sectors. Figure 17a-h shows dTEC maps from 01:20 to 02:30 UT. In Europe, midlatitude regions recorded strong northwest-to-southeast LSTIDs, which intensified over time. The polar ionosphere exhibited intense dTEC depletion, while Japan displayed a contrasting trend. Although northeast-to-southwest LSTID traces were observed at 01:20 UT, these weakened as the SYM--H reached its minimum and were nearly undetectable by 01:50 UT. Around 02:10 UT, LSTID activity intensified. North America showed strong LSTID traces, again oriented southwestward, which strengthened with decreasing SYM--H and subsided during the recovery phase. These observations align with those reported by [PERSON] et al. (2022) [7] during the September 2017 storm and [PERSON] et al. (2025) [5] during the May 2024 superstorm. [PERSON] et al. (2010) [24] found a strong correlation between auroral electrojet (AE) activity and LSTID amplitudes. Our results reinforce the idea that storm-time conditions--intensified thermospheric westward wind--enhance GW generation, which in turn drives LSTID propagation globally. The coincidence of a strong electric field and enhanced thermospheric circulation--both components of magnetosphere-ionosphere-thermosphere coupling--further suggests that LSTIDs during intense geomagnetic storms are linked not only to GW dynamics but also to electrodynamic plasma instabilities. The storm-time electric field may act as a trigger for plasma instabilities with rapid growth rates, ultimately contributing to TID generation and evolution, as proposed by [PERSON] et al. (2022) [25]. Although the global dTEC maps mentioned above provide dense coverage over the Northern Hemisphere, their resolution is significantly lower in the Southern Hemisphere, particularly over the Asian sector. To investigate the ionospheric response to the geomagnetic storm in the Southeast Asian region, we utilized ROTI data from the Ina-CORS GNSS network. Figure 17: **(a-h)** LSTIDs detected in the global dTEC map over the Northern Hemisphere on 10 October during **(a)** 01:20 UT, **(b)** 01:30 UT, **(c)** 01:40 UT, **(d)** 01:50 UT, **(e)** 02:00 UT, **(f)** 02:10 UT, **(g)** 02:20 UT, and **(h)** 02:30 UT. Figure 18a-c display the storm-time ROTI maps for this region. Figure 18a shows the ROTI distribution during the initial phase of the storm, specifically from 15:00 to 17:00 UT on 10 October. It is important to note that the local time (LT) in this region is approximately 7.5 h ahead of UT, placing this interval during nighttime conditions. As seen in Figure 18a, significant ROTI perturbations exceeding 1 TECU/min are evident in the Southern Hemisphere sector. These irregularities began to emerge around 15:15 UT, intensified by 15:40 UT, and started to diminish after 16:45 UT. A distinct southwestward propagation of these structures can be observed. Similar findings were reported by [PERSON] et al. (2025) [PERSON] et al. (2025) during the Mother's Day 2024 superstorm, where enhanced ROTI values were observed during post-sunset hours across Southern Australia. They attributed these enhancements to either the equatorward expansion of auroral activity or the influence of the midlatitude trough.