Velocities involved in Eqs. (1) and (2) for iron. The absolute velocity values in cm s⁻¹ are plotted vs. the optical depth. The thick dash-pointed grey curve shows the wind velocity (V_W, always positive). V_D and V_D + V_drag for the stationary solutions are plotted in blue and red, respectively. Positive velocities have vertical bar markers, and negative velocities have horizontal bar markers.