Upper row: time evolution of the average LOS velocities computed within the 5 × 5 px² green box shown in Fig. 7. The vertical bars indicate ± the standard deviation of the velocities within the same box. The overplotted red dashed line shows the average intensity in the blue wing of Na I D₂ inside of the same green box. The arrow marks the time of simultaneous GRIS data. Lower row: average intensity profile generated within the same green box. The color code indicates the time of each profile. The dashed vertical line marks the wavelength at rest. The dotted profile represents the quiet-Sun profile whereas the dashed one corresponds in time to the average profile marked with the arrows in the above panels.