# Interplanetary Magnetic Field Bx Effect on Field-Aligned Currents in Different Local Times
## 3 Results
The average value of Em remains below 0.8 mV/m, indicating a relatively quiet study period. In the dusk sector, as shown in Figure 3a,b, and Tables 1 and 2, the intensities of FACp during the local summer are higher than those during the local winter. This is mainly due to the ionospheric conductivity effect, as illustrated in Figure 3g,h. The seasonal variation in FACe (Figure 3c,d) shows an opposite trend to the conductivity driven by sunlight but follows a pattern similar to that of Em (Figure 3e,f), suggesting that FACe is more influenced by Em. In the dawn sector, both FACp and FACe are impacted by conductivity, with values larger in summer than in winter (Figure 3a-d). It is notable that the seasonal difference in conductivity is more pronounced than that in the FACs, likely due to the counteracting influence of Em (Figure 3e,f). In the 21-02 MLT region, the downward FACs (FACp, Figure 3a,b) exhibit significant seasonal fluctuations in two hemispheres, with stronger intensities in summer compared to those in winter. This increase in FACp during summer is primarily due to changes in ionospheric conductivity (Figure 3g,h). Enhanced solar radiation leads to an increase in electron densities, which increases conductivity and, in turn, increases the FACp intensity. This pattern is consistent across both hemispheres, with FACp being stronger during local summer. On the other hand, upward FACs (FACe, Figure 3c,d) show greater intensity in winter than in summer, which may be attributed to energetic particle precipitation effects. According to [PERSON] et al. (1996) [23], high-energy electron precipitation associated with upward FACs can be suppressed at night by solar illumination. This ionospheric feedback effect may reduce the influence of solar radiation on upward FACs during night, a finding also supported by [PERSON] et al. (2005) [4]. In the Southern Hemisphere (SH), the seasonal variation in FACe is relatively small, likely influenced more by changes in ionospheric conductivity due to particle precipitation than by solar illumination alone. In the MLT sector of 09-14, both FACs are notably stronger in summer than in winter (Figure 3a,b). Figure 4 illustrates the differences in FAC strength and latitude between cases where the IMF cone angle is \(\leq\)45\({}^{\circ}\) and \(\geq\)135\({}^{\circ}\). A positive value indicates a stronger current and a higher latitude when the IMF cone angle is \(\leq\)45\({}^{\circ}\) (i.e., IMF Bx \(>\) 0) compared to when the IMF cone angle is \(\geq\)135\({}^{\circ}\) (i.e., IMF Bx \(<\) 0). The June solstice is marked with an asterisk, and the December solstice is marked with a circle. Blue lines represent the Northern Hemisphere, while red lines represent the Southern Hemisphere. In MLT sectors dominated by westward PEJ (MLTs of 21-02, 03-08, and 09-14 with PEJw), the FACp intensity exhibits a stronger dependence on IMF Bx compared to sectors occupied by eastward electrojets (i.e., MLTs of 15-20 and 09-14 with PEJe). In the 21-02 MLT sector, both FACp and FACe responses are more pronounced during the local summer than the local winter, with FACe showing weaker responses than FACp during the summer. In JuneS, the NH exhibits a larger AFACp for IMF cone angles \(\geq\) 135\({}^{\circ}\) compared to those \(\leq\)45\({}^{\circ}\). Conversely, in DeceS, the SH shows a greater \(\Delta\)FACp for IMF cone angles \(\leq\) 45\({}^{\circ}\) than for those \(\geq\) 135\({}^{\circ}\). In both hemispheres during the local summer, AFACe is generally stronger for IMF cone angles \(\geq\) 135\({}^{\circ}\) than for those \(\leq\)45\({}^{\circ}\). Figure 3: Absolute peak values of FACp (**a,b**), FACe (**c,d**), merging electric field (Em, (**e**,f**)), ionospheric conductivity (\(\Sigma\)H, (**g,h**)), and IMF Bx for IMF cone angles \(\leq\) 45\({}^{\circ}\) (**i**) and \(\geq\)135\({}^{\circ}\) (**j**) plotted against MLT. Asterisks indicate the June solstice, and circles indicate the December solstice.