Spectra of the total intensity of the CN (N, J, F) → (N′, J′, F′) = (1, 1/2, 1/2) → (0, 1/2, 1/2) transition excited in a TW Hya-like proto-planetary disk in an emission surface around z/r = 0.3, with (lower row) and without (upper row) a layer of dust present between the emission surfaces. In each panel the spectra for different optical depths (left to right) and azimuthal angles (different colors within the panels) are given. The dashed lines are from spectra assuming no magnetic field permeating the disk.