Time evolution of fine structures of a main sunspot in the SD108 and SD284 groups

Abstract

Photoheliograms taken at the Pamir Mountain Station (spatial resolution 0.3 arcsec) centered on 650 nm with a 40 nm bandwidth are used to obtain a standardized sequence of images for the dynamical study of some umbra and penumbra details of the main sunspot. Our images show, through visual inspection, the presence of bright and dark filaments in the penumbra. However, a clear indication of two distinct photometric levels was not found. A temporal variation of the characteristic penumbra intensity value was detected, which will be investigated later. Umbral dots and nuclei were detected and their spatial distributions were analyzed. A characteristic value for the umbral dots diameter was obtained.