Hanle effect on the line-core polarization of the Mg I triplet. The lines are obtained close to solar limb (μ = 0.1) in presence of a horizontal magnetic field of various strengths, 0 G (solid lines), 0.005 G (dotted lines), 0.1 G (dashed lines), 1 G (dot-dashed lines), 10 G (triple-dot-dashed lines), and 100 G (long dashed lines). The top six panels show the Q/I and U/I profiles with the azimuth χ_B = 30°, and the bottom six panels show the Q/I and U/I profiles with the azimuth χ_B = 0°. The other parameters are the same with those producing Fig. 4.