The Lifetime and Cell Size of the Granulation in Sunspot Umbrae

Abstract

High quality photographs extending over a period of 2 hr 11 min have been obtained of the granulation in the umbra of a large sunspot. In agreement with earlier work, the mean cell size of the umbral granulation is found to be significantly less, and the lifetime considerably greater, than that of the photospheric granulation. Ten per cent. of the umbral granules last for over 2 hr.