Comparison of fibril orientation and chromospheric field azimuth from the spatially-regularised WFA and the MHS model. The background Ca II 8542 Å image has been unsharp masked with a radius of 05 to enhance fibrillar structures. The azimuth is indicated by yellow (WFA) and red (MHS) bars, where arrowheads have been omitted since we did not resolve the 180°-ambiguity for the WFA. The three white boxes in the left-hand panel a indicate the selections presented as panels b–d in the right-hand column and have been chosen such as to contain part of the ROIs in Fig. 1, where panel b covers ROI 1, panel c ROIs 2 and 3, and panel d ROI 4.