Polarisation maps for a purely toroidal magnetic field and a BES density distribution (model radius, r_model = 2.25 × 10⁴ AU). Black vectors represent the direction of the magnetic field, whose length is proportional to the fractional polarisation, obtained by flipping by 90 degrees the dust polarisation vectors. White contours show 50 and 90 per cent of the 850-μm dust emission (Stokes I) peak and the coloured map depicts the polarised flux intensity (I_p). The scale bar to the right gives I_p in Jy/(10′′ beam). The inclination of the models with respect to the plane of the sky is given in the upper left corner of each subplot. The synthesised beam is shown in the lower left corner.