SPECKLE IMAGING OF SOLAR SMALL-SCALE STRUCTURE .2. STUDY OF SMALL-SCALE STRUCTURE IN ACTIVE REGIONS

The speckle imaging technique which is described in the first paper of this series (von der Luhe 1993) was used to analyze time series of hi gh angular resolution images of solar small scale structure at a wavel ength of 585 nm in active regions with the 76cm diameter vacuum tower telescope at NSO/Sac Peak. Two sets of reconstructed images with a fie ld of 4 by 4 arcsec which cover a period of 36 min and 83 min were gen erated and analyzed. The image reconstructions are supplemented with s imultaneous large field photographs taken within a 15 angstrom passban d centered on the Ca II K (3933) line. The prime objective of the obse rving program was the study of the structure and the dynamics of the c ontinuum wavelength counterpart of facular points which appear with hi gh contrast in the Ca pictures, i. e., continuum bright points (CBPs). In addition to CBPs, the reconstructions allow studying other small s cale phenomena. The studies have led to the following results: Reconst ructed images of CBPs have full width at half maximum dimensions betwe en some 120 km and some 500 km, and peak brightnesses ranging from 1.0 5 to 1.6 times mean intensity of the reconstructed field. These charac teristics agree well with the intensity characteristics of the models described by Deinzer et al. (1984b) and Knolker et al. (1988). Nearly all observed CBPs in our small sample are elongated. Larger reconstruc ted CBPs with a ratio of longest to shortest dimension exceeding 2 sho w signs of internal structure which can be explained by a collection o f several CBPs which are not fully resolved. There are signs of rapid evolution within CBPs. The reconstructions indicate that abnormal gran ulation is related with and confined to areas which show strong emissi on in the Ca pictures (Ca faculae). The continuum intensity fluctuatio ns have scales smaller by 20% ... 30% and increased rms contrast by 1% ... 2% compared to granulation in areas free of Ca faculae. There is a sharp boundary between normal and abnormal granulation. In general, the position of CBPs appear to be remarkably stable compared to the ev olution of nearby granules. However, large velocity gradients may occu r over short distances. The relative proper motion between two CBPs wi th a minimum separation of 200 km was measured to be as large as 1 km/ s, with the velocity vector perpendicular to the line of connection of the CBPs. The continuum may show structure which resembles penumbral filaments without an associated sunspot or pore for periods of the ord er of 10 min.