Magnetic configuration of the higher coronal null-point (Fig. 8d) and its relationship with the main FR depicted on 21 April 2013 at 18:00 UT, when the main FR was just forming. Panel a: field-line configuration around the null-point (orange-white lines), the main FR (green-white lines), and field lines originating from Region 3 in panel b (black-white lines). The photospheric distribution of B_z is shown in gray scale (saturated at ±100 Mx cm⁻², black for negative) and blue/red contours (±100 Mx cm⁻², blue for negative). The purple-to-white color plot shows the magnetic squashing factor log₁₀Q at horizontal plane z = 0.729 Mm ranging from 1 to 5, shown only in high-Q regions where log₁₀Q ≥ 1.25. The blue-red color plot shows the twist number in the same horizontal plane including only the regions where [(log₁₀Q ≤ 1.25)∧(T_w ≤ −0.25)]. Panel b: zooms into the positive-polarity photospheric footpoints of the field-line systems in panel a. The dashed lines outline regions of consistent magnetic connectivity for each field-line system, labeled Regions 1–3 with coloring consistent with that of panel a. The black patch in Region 2 shows the position where the footpoints of the main FR start to appear. An animated version of panel b is available online.