Randomly chosen field lines representing the best-fit model (model S, see right panel in Fig. A.1) after relaxation. The x and y coordinates are in model coordinates viewed from top down on the region. Some of the field lines are sheared and some are twisted, mostly along the PIL of the parasitic positive polarity and the negative leading polarity of the active region. Away from this region, the field lines are mostly low-lying arcade loops, while the northern region has open field lines surrounding the HFT region (Sect. 4).