Stokes Q/I (top panels), U/I (middle panels), and V/I (bottom panels) profiles for the He II Ly-α line as a function of wavelength. The results are obtained with the FAL-C atmospheric model, with a uniform horizontal (θ_B = π/2 and χ_B = 0) magnetic field of 100 G, and for two LOSs, near the limb (μ = 0.1, left panels) and near the disc centre (μ = 0.9, right panels), respectively. Blue, red, and yellow lines correspond to CRD, PRD–AA, and PRD–AD calculations, respectively. The unmagnetic CRD and PRD–AD cases are given for reference as dash-dotted and solid black lines, respectively.