Mean magnetic-field strength maps used as inputs for the CRPropa simulations, shown in face-on (left panel) and edge-on (right panel) projections. The model consists of three logarithmic spiral components centred at APC 1 (0.9 kpc, 0.25 kpc), APC 2 (0.5 kpc, −0.5 kpc), APC 3 (−0.8 kpc, −0.1 kpc) following the star-forming regions identified by Buzzo et al. (2021). A spiral pitch angle of 12° and an X-shaped halo field with an opening angle of 50° are adopted to define the large-scale 3D field structure.