LOS velocity measured with the Ca I 10 839 Å line (panel a), Si I 10 827 Å line (panel b), Fe I 5435 Å line (panel c), and He I 10 830 Å triplet (panel d). The signals have been filtered in the frequency range between 1 and 15 mHz. Positive velocities (red) correspond to downflows and negative velocities (blue) to upflows. The vertical colored lines indicate the umbral location illustrated in Fig. 3.