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High resolution spectropolarimetric observations by Hinode reveal theexistence of supersonic downflows at the umbra-penumbra boundary of 3 sunspotsthat was recently reported by Louis et al. (2010). These downflows are observedto be co-spatial with bright penumbral filaments and occupy an area greaterthan 1.6 arcsec$^2$. They are located at the center-side penumbra and have thesame polarity as the sunspot which suggests that they are not associated withthe Evershed Flow. In this paper we describe the supersonic velocities observedin NOAA AR 10923 and discuss the photospheric as well as chromosphericbrightenings, that lie close to the downflowing areas. Our observations suggestthat this phenomenon is driven by dynamic and energetic physical processes inthe inner penumbra which affect the overlying chromosphere and thus provide newinsights for numerical models of sunspots.

Observations of Supersonic Downflows Near the Umbra-Penumbra Boundary of Sunspots as Revealed by Hinode