Comparison of magnetic field orientations between model and observations. Upper panel: magnetic field configuration inside a radius of 3700 au, corresponding to the radius of the Main core in G31, obtained with b₀ = 0.1, λ = 2.66, i = 50°, and ϕ = −63°. Lower panel: magnetic field segments from observations at 1.3 mm (red) and the best model (blue). The grey-scale map shows the polarized intensity, P, while black contours show the 1.3 mm dust emission at 5, 10, 30, 60, 120, 160, and 200 times σ, which is 0.15 mJy beam⁻¹. Yellow areas show the regions where the difference between the observed and modeled polarization angle is |Δψ| > 45°. The inset shows the distribution of the polarization angle residuals obtained considering the whole range of Δψ (green) and limited to |Δψ| ≤ 45 deg (magenta). The solid lines show the corresponding Gaussian fits to the histograms.