Snapshots showing the evolution of the FRs. Snapshots are extracted from the TMFM simulation (normalised simulation times with respect to the flux evolution; see Sect. 3.4: 0.33, 0.63, 0.92, 1.21) and the MHD relaxation (normalised times: 0.86, 1.03, 1.19, 1.36) originating from AR12473, which is associated with the solar eruption on 28 Dec. 2015. The FR extraction method used an ϵ value of 0.03 in the TMFM case, and 0.04 for MHD (see text for details). The vertical magnetic field B_z at the photospheric boundary is shown at the bottom. Movies are available online.