transit. The data obtained in this study provide evidence for the existence of running umbral
waves in the chromosphere. These waves have a period of 2.8 min and propagate from the
sunspot center outward with the phase velocity of 45–60 km s-1 with the line-of-sight velocity
amplitude of about 2 km s-1. In most cases the waves terminate rather abruptly on the umbra
boundary and show no direct linkage with running penumbral waves. The spatial coherence …