Dynamics of the solar active region finestructure

We investigate the dynamical behavior of the finestructure in a sunspotʹs surroundings and its penumbra from a speckle-reconstructed 60 min time series taken at the 45 cm Dutch Open Telescope (DOT) on La Palma. In the 1 nm spectral window containing the G-band, we determine the area of each feature and its time evolution by means of pattern recognition, particularly adapted to separate bright granular edges from inter-granular G-band bright points (BP). The evolution of each individual BP shows a stronger variation of the area than of the intensity. We analyze the horizontal motions of BP as a function of their distance from the sunspot center. Within a 6 Mm ring around the outer sunspot border, most BP (4/5) move radially outwards; they are faster than the minority (1/5) of inward moving BP. The difference of both velocities indicates a radial outward drift which decreases from about 0.3 km s -1 at the outer penumbral border to zero at about 20 Mm distance (28´´) from the sunspot center; a spatial range that we interpret as the extension of the sunpot "moat". This finding supports the idea of giant rolls in deep layers measured by helioseismic tomography and predicted by theory. Inside the penumbra, we find a 4/5 majority of penumbral bright structures (PBS) to move inwards with a mean velocity of 0.8 km s -1. The 1/5 minority of outward moving PBS is almost entirely located in the outer penumbra; their mean velocity of 0.8 km s -1 is equally found for penumbral dark structures (PDS) in the outer penumbra, in agreement with penumbral MHD models.