Magnetic field topology showing two adjacent fan-spine structures. The 3D null 1 shown here is the same as in Fig. 3. The UV brightening is located close to the 3D null 1. The inner spines of the two 3D nulls are rooted in different negative polarity patches, with their fan footpoints at nearby positive polarities. The QSEB is shown in yellow colour in Hβ –0.6 Å image for better visibility among a large number of magnetic field lines. QSEB-C is located at the shared fan surface footpoints of both the 3D nulls. Panel (b) shows the B_LOS map with contours at 2σ above the noise level with different markers: orange cross markers denote the inner spine footpoint of the 3D null 1 and yellow circles denote the footpoints of its fan surface. The blue crosses denote the position of the inner spine footpoint of the 3D null 3, and the red circles show the footpoints of its fan surface. The location of QSEB-C is marked with a blue star. The log Q plane is displayed close to the photosphere, where regions in red denote high values of Q. Yellow arrows in both panels show the direction towards the limb.