Normalized polarization degree p/p₀ as a function of azimuthal angle for observing wavelength of λλλ 3.5,6.2,20.5 cm for each of the four rings for a two-layer model. Columns provide the polarization profiles per ring at a fixed observing wavelength while rows provide polarization profiles at all three observing wavelengths at a fixed ring. 0° corresponds to the north major axis of M 51 with sectors counted counterclockwise. The solid black points correspond to the predicted polarization value, at each azimuth, from the best-fit magnetic field strengths. The shaded gray region corresponds to the range of polarization values predicted by all regular disk and halo magnetic field configurations encompassed by the solid, contour in Fig. 1 for rings 1, 3, 4 and in Fig. 2 for ring 2. The turbulent magnetic fields are the same as described in Table 4. The following sectors have been discarded as they are outliers (see text): sector at 60° for the inner two rings, and sectors at 220°, 300°, and 320° in the outermost ring.