(a)–(b) Synthetic magnetograms for the FR emergence model with N_t, 0 = 0.5 (h = 0, g = 0) at two different time steps of the evolution. The red and blue dashed-contours correspond to the |B_z| = 50 G isocontours of the axial field map (Fig. 1a). The magnetic field strength on the FR axis is set to 1000 G. The red and blue dots show the position of the magnetic barycentres of the axial map and the black segment in between indicates an intrinsic tilt ϕ_i = 0. The |B_z| = 50 G isocontours of the total map (see also Fig. 1c) are drawn with magenta continuous lines. The magenta line that joins the total map barycentres indicates an apparent tilt ϕ_a. (c) Evolution of ϕ_a for the uniform-twist models with N_t, 0 = 0, 0.2, 0.5, 0.7 (black, red, green and blue continuous lines, respectively). The non-uniform twist models have a fixed value of N_t, 0 = 0.5 and (h, g) values indicated between brackets (violet, yellow, orange, and brown continuous lines, respectively). The associated movie is available online (fig2_a.avi).