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