Comparison of field lines in selected extrapolations from the ensemble. First row: Field lines randomly sampled from the entire bottom boundary. Second row: Same as above, but the low current density regions are transparent. Third row: Field lines corresponding to the area inside the J-shaped flare ribbon. Bottom row: Field lines corresponding to the dimming region as defined by all pixels below the threshold of −0.5 in the logarithmic AIA 211 Åbase ratio image of 20:35 UT (see Sect. 3.2 for more details). In the visualizations of λ_ff = 0.4, two subregions are marked that correspond to the subregions for which the quality metrics given in Table A.1 were calculated.