# Interplanetary Magnetic Field Bx Effect on Field-Aligned Currents in Different Local Times
## 3 Results  
This study utilized the superposed location analysis method to analyze FACs. The FAC data were averaged over a reference latitude range of \(-10^{\circ}\) to \(10^{\circ}\), with a \(2^{\circ}\)\(\Delta\)MLat bin size. The reference latitude (\(\Delta\)MLat = \(0^{\circ}\)) was defined by the location of the peak PEJ, where negative values represent equatorward regions, and positive values represent poleward regions relative to the reference latitude. Figure 2 displays the latitudinal distribution of FACs during periods when the IMF cone angle is \(\leq\)45\({}^{\circ}\) and \(\geq\)135\({}^{\circ}\). Each subfigure contains five colors, which correspond to specific MLT sectors. All data are categorized by season and hemisphere. In the 15-20 MLT sector, a prominent presence of upward FACs is observed on the polar side of the reference latitude, alongside significant downward FACs on the equatorward side. These observations are consistent with the typical characteristics of R1 and R2 FACs, as well as eastward PEJ currents at dusk. At 21-02 MLT sector, the downward FACs are poleward of the westward PEJ, while the upward FACs are equatorward of it. Typically, three distinct current sheets appear around midnight, closely associated with  
Figure 2: The superposed location analysis results for FACs in the NH (**a**,**c**,**e**,**g**) and SH (**b**,**d**,**f**,**h**) at four magnetic local times for IMF cone angles \(\leq\) 45\({}^{\circ}\) (**a**–**d**) and \(\geq\)135\({}^{\circ}\) (**e**–**h**). The rows represent JuneS (June solstice, (**a**,**b**,**e**,**f**)) and DeceS (December solstice, (**c**,**d**,**g**,**h**)). The reference position is set as \(0^{\circ}\) AMLat, marking the maximum intensity of the auroral electrojet. Regions with negative \(\Delta\)MLat values lie towards the equator relative to the peak of the electrojet, while regions with positive \(\Delta\)MLat values are positioned on the polar side of the maximum auroral electrojet. Error bars denote the standard error of the mean. abrupt changes in the electric field and current direction at the Harang discontinuity. This discontinuity causes the central FACs to flow outward from the ionosphere, while FACs on both sides flow inward, forming this specific current distribution pattern. At the 03-08 MLT sector, typical FACs suggest downward R1 (upward R2) currents centered around the westward PEJ. Meanwhile, at the MLT sector of 09-14, one can observe the midday R1 FACs at lower latitudes and midday R0 FACs at higher latitudes, with the current directions influenced by the orientation of IMF By. Prominent upward or downward R0 FACs and downward or upward R1 FACs co-occur with eastward or westward PEJ, depending on the orientation of IMF By and subsequent PEJ. In this study, we use the labels FACp for FACs located on the polar side and FACe for those on the equatorial side. This terminology helps to clarify and deepen our understanding of these phenomena. Specifically, FACp denotes R1 FACs, whereas FACe denotes R2 FACs during dusk and dawn. In the MLT sector of 09-14, we use FACp to represent R0 FACs at noon, while FACe represents noontime R1 FACs. In the MLT sector of 21-02, FACp denotes the current entering the ionosphere, whereas FACe denotes the current leaving the ionosphere. This naming scheme enhances our ability to identify and analyze FAC characteristics across different times and locations. Figure 3 shows the maximum values of FACp and FACe, as observed during the June (marked with asterisks) and December (marked with circles) solstices, for IMF cone angles \(\leq\) 45\({}^{\circ}\) and \(\geq\)135\({}^{\circ}\) across five local time sectors. Additionally, the bottom two panels of Figure 3 present the zonal variations in Em, ionospheric conductivity (\(\Sigma_{\rm{H}}\)), and IMF Bx for comparison. The data corresponding to Figure 3 are provided in Tables 1 and 2. For each peak PEJ event, the mean Em and ionospheric Hall conductivity values due to sunlight are calculated [22].