Predictions of polarised emission for a RT model with constant grain alignment, using the toy magnetic field model. The figure is the same as in Fig. 18 except that the transition from the large-scale field to different field orientations in the filament takes place at a higher threshold of n(H₂) = 10⁴ cm⁻³. The polarisation vectors are shown on the column density map in panel a and the p vs. N(H₂) relation is plotted in panel b at Planck resolution. The lower panels are the corresponding plots for synthetic POL-2 observations.