# Correlation Study of Auroral Currents with External Parameters During 10-12 October 2024 Superstorm
## 4 Discussion
### Mean Current Density and Latitude  
R1 and R2 FACs and PEJs on the dawnside were higher than those on the duskside in the summer (i.e., southern) hemisphere during this October storm. Such dawnside preference in the summer hemisphere is consistent with the May 2024 storm [10]. This preference can be explained by the combined (mutually canceling) influence of the convective electric-field-driven westward DP-2 current and the substorm-driven westward DP-1 current at dawn (dusk). However, during the May storm, both FACs and westward PEJs in the winter (i.e., southern) hemisphere showed higher values at dusk than at dawn, as the substorm DP-1 current extended more into the duskside in the winter hemisphere [10]. Figure 7: The Spearman correlation analysis between PEJ MLat and seven external parameters. (**a,c**) Northern Hemisphere and (**b,d**) Southern Hemisphere. Different colors denote different local times. Brown and yellow are for duskside eastward (J+) and dawnside westward PEJs (J\(-\), (**a,b**)) and for daytime and nighttime westward PEJs (**c**), (**d**), respectively. The highest correlation coefficients are further denoted by half gray bars. Clearly, this duskside extension of intense westward DP-1 currents did not occur during this October storm, and as a result, both PEJs and R2 FACs on the dawnside were still higher than on the duskside. During this October storm, the downward FAC density on the dayside was generally greater than at night in the two hemispheres. In the summer pole, the PEJ density during the daytime also exceeded that during the night, consistent with the results of the May 2024 storm event [10]. These phenomena are mainly related to ionospheric conductivity variations induced by solar illumination, where the daytime experiences stronger sunlight than the nighttime, leading to significantly higher conductivity on the dayside compared to the nightside. Conversely, the upward FAC density on the nightside exceeds that on the dayside, and in the winter hemisphere, the PEJ densities during the day and night are comparable. This can be attributed to the important influence of energetic particle precipitation on the nighttime conductivity, which primarily affects the upward FAC region. Notably, the daytime-nighttime differences in FAC densities varied between the May and October storms: in the May storm, the upward FAC density on the dayside was higher than that on the nightside in the summer hemisphere, while in the October storm, the upward FAC density on the dayside was lower than on the nightside in the summer hemisphere. This suggests that the differences between the two hemispheres are not only simply related to seasonal variations but may also be influenced by geomagnetic geometry differences between the hemispheres. For example, the magnetic dipole tilt angle (the angle between the geographic and geomagnetic axes) in the Southern Hemisphere is larger than in the Northern Hemisphere, which might affect the sunlight intensity and particle precipitation processes in the two hemispheres [24]. During this October storm, most FACs in the summer hemisphere were stronger than those in the winter hemisphere, with the exception of the downward FACs on the nightside, which is generally consistent with the May storm results [10]. These hemispheric differences might come from the larger ionospheric conductivity in the summer than the winter hemisphere. Those subtle differences lie in the fact that during the October storm, the downward FACs at night were more intense in the winter than in the summer hemisphere, while for the May storm, the upward FACs at night were more prominent in the local winter than in the local summer hemisphere. PEJs in the daytime and dusk are higher in the summer hemisphere when compared to the winter hemisphere, confirming the May storm results, which is due to seasonal variations in ionospheric conductivity. In the evening and dawn sectors, PEJs are stronger in local winter than in local summer; however, in the May storm, both hemispheric PEJs were quite comparable.