Two extrapolations of the magnetic field using a skirt of ten pixels around the original magnetogram to enforce flux balance and one extrapolation without the skirt. Left: MS model extrapolation, middle: potential extrapolation, and right: potential extrapolation of the original data with the boundary smoothing to remove the signal to enforce a periodic setup. The field lines represent the magnetic field line structure around the null point associated with the BP1 case (see the discussion below).