# Correlation Study of Auroral Currents with External Parameters During 10-12 October 2024 Superstorm
## 3 Results  
Throughout the storm period of 10-12 October 2024, Swarm orbits primarily remained within the same local time sector in the Sun-Earth reference frame. Specifically, Swarm A and C satellites were positioned near the dawn-dusk meridian (\(\sim\)6 and \(\sim\)18 MLT), while Swarm B was located in the daytime-nighttime sector (\(\sim\)10 and \(\sim\)22 MLT). This orbital configuration provided a unique opportunity to investigate the relationship between large-scale FACs and PEJs and solar wind IMF parameters for four local time sectors, including day, night, dawn, and dusk. Furthermore, the interhemispheric comparison allowed for the exploration of hemispheric/seasonal asymmetries. The hourly mean solar wind/IMF parameters and Dst variations from 10 to 12 October 2024 are illustrated in Figure 1. The event analyzed was triggered by a CME observed in the solar wind. The solar wind speed (Vsw) was greater than the background (Figure 1d). The solar wind mass density (Nsw) and dynamic pressure (Pd, Figure 1c,e) showed pronounced variations, which were typical CME characteristics. The IMF By component underwent a sign change shortly before the Bz component reached its minimum, which was consistent with the passage of the CME-related flux rope (Figure 1a,b). The sudden storm commencement occurred around 15 UT on 10 October (see the black vertical dashed line) due to a jump in Pd (Figure 1e). Dst attained its minimum of about \(-341\) nT around 25 storm-time (see the blue vertical dashed line) before slowing and returning to \(-50\) nT on 12 October (Figure 1g). During the storm's main phase, IMF Bz remained predominantly southward and reached a minimum value of approximately \(-41\) nT at 24 storm-time (Figure 1b). Pd attained two peaks, 30 and 25 nPa, around 16.5 and 21 storm-time within the storm's main phase (Figure 1e). One can notice that Pd and Nsw reached two peaks simultaneously; however, Vsw changed more gradually. The second peak in Pd was lower than the first, while for Nsw, the second peak was comparable to the first. As a result, we attribute the Pd surge to the combined contributions of both Nsw and Vsw. It is also worth noting that Em reached several peaks throughout the storm's main and recovery periods (Figure 1f). Peak upward and downward FACs were selected out for each satellite's orbit crossing the auroral region during the magnetic storm. The storm-time variation in peak FAC density and latitude together with the Dst index are shown in Figure 2. The circle size indicates FAC densities, with red (blue) depicting upward (downward) currents flowing out of (into) the ionosphere. The maximum upward and downward FAC densities throughout the storm periods are marked by red and blue dots. The most equatorward latitudes of upward and downward FACs are highlighted in brown and green. The left and right panels represent the Northern and Southern Hemispheres, respectively. Figure 1: The storm-time variations in solar wind IMF parameters, including GSM IMF By **(a)**; IMF Bz **(b)**; solar wind mass density, Nsw **(c)**; solar wind velocity, Vsw **(d)**; dynamic pressure, Pd **(e)**; merging electric field, Em **(f)**; and Dst **(g)** variations on 10–12 October 2024. Storm-time means hours beginning at 00 UT on 10 October 2024. The time interval enclosed by the black and blue dashed lines indicates the main phase. Compared to the quiet period before 15 UT on 10 October 2024, the FAC density increased significantly during the magnetic storm, as bracketed by gray vertical dashed lines. The maximum values of upward (red dots) and downward (blue dots) FACs generally appeared during the main phase of the storm.