  High-resolution spectropolarimetric observations of active region NOAA 11271
were obtained with the spectro-polarimeter on board Hinode to analyze the
properties of an anomalous flow in the photosphere in a sunspot penumbra. We
detect a blue-shifted feature that appeared on the limb-side penumbra of a
sunspot and that was present intermittently during the next two hours. It
exhibited a maximum blue-shift of 1.6 km/s, an area of 5.2 arcsec^2, and an
uninterrupted lifetime of 1 hr. The blue-shifted feature, when present, lies
parallel to red-shifts. Both blue and red shifts flank a highly
inclined/horizontal magnetic structure that is radially oriented in the
penumbra. The low-cadence SP maps reveal changes in size, radial position in
the penumbra and line-of-sight velocity of the blue-shifted feature, from one
scan to the other. There was an increase of nearly 500 G in the field strength
and a marginal reduction in the field inclination of about 10 deg with the
onset of the blue-shifts. In the chromosphere, intense, arc-shaped brightenings
were observed close to the location of the blue-shifts, that extend from the
edge of the umbral core to the penumbra-quiet Sun boundary. The strongest and
largest brightenings were observed about 30 min after the strongest blue-shifts
were detected at the photosphere. The close spatial proximity of the two
phenomenon strongly suggests a causal relationship. The blue-shifted feature
represents plasma motion that could be related to a magnetic structure that
rises in the solar atmosphere and subsequently reconnects with the ambient
chromospheric magnetic field of the sunspot or an inverse Evershed flow, which
would be unique in the photosphere. This transient phenomena is presumably
related to the dynamic stability of the sunspot because the corresponding
umbral core separated two days later at the location of the blue-shifts and
fragmented subsequently.
