Two nested fan-spine magnetic field topologies obtained from potential field extrapolation. A smaller fan-spine structure (3D null 2) is located inside the fan surface of the larger one (3D null 1). The two fan surfaces share footpoints at two positive polarities, this is shown at a different angle in Fig. 3. QSEB-B is located at one of the shared footpoints of the fan-surfaces, shown in light blue and white shades in the Hβ –0.6 Å image placed close to the photosphere. The inset shows the zoom-in of 3D null 2 at a slightly different angle to clearly highlight the fan-spine configuration. The yellow arrow points to the direction of the north solar limb.