Facular Granule Lifetimes Determined with a Seeing?Monitored Photoheliograph

Abstract

A telescope designed to take exposures automatically at moments of good seeing has been used to obtain a 5! hr sequence of high quality photographs of a facular region near the east limb of the Sun. Individual facular granules are found to be much longer lived than the photospheric granules, a result which agrees with the work of ten Bruggencate (1940) and Waldmeier (1940) but disagrees with the more recent observations of Macris (1953) and of Krat and Goldberg-Rogosinskaja (1956). Fifty per cent. of the facular granules lasL for over 2 he, and 10% last for over 5 hr. In some cases, a facular granule, only 750--1500 km in diameter, occurs as an isolated bright structure, surrounded by normal photosphere and well removed from neighbouring sunspots or faculae. Apart from their greater brightness and much longer lifetimes, the facular granules differ from the photospheric granules in that they do not form awell-defined cellular pattern; these differences suggest different modes of origin