Results of step B. Top: histogram of ψ_R, the polarization angle inferred from the Stokes parameters rotated with respect to the best-fit uniform direction of the GMF ( and ), over the southern Galactic cap (black dots). The error bars represent the Poisson noise within each bin of the histogram. The green line represents the mean of the step B results for f_M = 0.4 over 20 different realizations. The green shaded regions correspond to ± 1σ (light green) and ± 2σ (dark green) variations of the model. Bottom: histogram of p² obtained when combining the Year 1 and Year 2 maps (black dots). The error bars here represent the Poisson noise within each bin of the histogram. Step B is now shown in blue. The dashed vertical line corresponds to a value of the polarization fraction of 12%.