Emergent I (upper panels) and Q/I (lowerpanels) profiles calculated in the FAL-C atmospheric model (N_s = 70), with Ν_θ = 12, N_χ = 8, and Ν_ν = 99, for the LOS with (leftpanels) and (rightpanels). The line line center frequency ν₀ is reported. A vertical bulk velocity field is considered (see Sect. 6.4). The reference direction for positive Q is taken parallel to the x-y plane (see Fig. 1). The PGMRES solver converges in five iterations.