Notes. The “Uniform” model assumes a uniform magnetic field orientation over each Galactic polar cap, “A18” is the spheroid model presented in A18, and “L19” and “LE19” are the models developed in this paper with the shape of theLB shell extracted from the L19 and LE19 3D extinction maps, respectively, each modeled with l_max = 6. The four models were fitted to the Planck PR3 353 GHz data. Listed here are the reduced χ², the effective polarization fraction, p₀, the orientation of the magnetic field averaged over each of the northern and southern polar caps, , and cos² γ averaged over each polar cap, with γ the angle of the magnetic field to the plane of the sky.