Upperpanel: magnetic field configuration inside a radius of 3700 au, corresponding to the radius of the Main core in G31, for b₀ = 0.1, i = − 45°, and φ = −44°. Lower panel:magnetic field line configuration for b₀ = 0.1 shown almost pole-on to emphasize the line twisting close to the symmetry axis. The spatial scale is the same in both panels (the model extends up to a radius of 3700 au). The color of the magnetic field lines indicates the magnetic field strength in both panels (see color scale in the bottom panel).