Comparison of the I_m, Q_m, and U_m power spectra extracted from the Planck Polaris Flare maps (grey points representing the two-dimensional power spectra, and black dots representing the azimuthal averages in Fourier space) with the observables computed from simulations using the best fitting parameters (blue curves). The latter curves are averaged over 60 realizations as described in Sect 4.2: the average is given by the central blue curve and the narrow shaded bands give the 1σ and 2σ standard deviation in each bin.