EVOLUTION OF SMALL-SCALE STRUCTURES IN AND AROUND A LARGE SOLAR PORE

摘要

The analysis of an 11-hour series of high resolution white light observations of a large pore in the sunspot group NOAA 7519, observed on 5 June 1993 at the Swedish Vacuum Solar Telescope, La Palma, Canary Islands, is described. We used a total of 1782 frames, with average time interval of 22 s. Special attention was paid to the evolution of a filamentary region attached to the pore, to horizontal motions around the pore, and to small-scale morphological changes. The filamentary region was observed to change its structure back and forth between penumbra-like filaments and elongated granules. A clockwise rotation of this region around the center of the pore was detected during the whole observing period. This rotation had angular velocities decreasing with time from 7.6° h~(-1) to 2.7° h~(-1). Motions inside the filamentary region and around the pore, including penetrations of photospheric granules into the pore, were studied in detail using local correlation and feature tracking algorithms. It was found that the observed filamentary region, although having some typical penumbral features, was different from a normal penumbra.