Null point above the flux rope, which is marked as a red star. (a)–(b) Different view of the null point. Magnetic field lines traced from different topological structures are shown in different colors. The iridescent lines belong to the flux rope, while the gray lines are for the coronal configurations associated with the null point. (c) The distribution of logarithmic Q in a vertical plane crossing the magnetic null. The position of the plane is indicated by a semi-transparent cut in panel a. The photospheric B_z in panels a and b saturates at ±2000 G.