Patches representing the regions where horizontal RT enhances the NLTE effects (white), weaken the NLTE effects (black), or has no significant influence (grey). From left to right, we show this for T, v_LOS, B, and γ at all the three inversion nodes; from top to bottom log(τ) = − 2.0, −0.9, and 0.0. The threshold values employed to divide the regions into the three categories are indicated in the colour bar. See Sect. 5 for further details.