Faculae and east-west asymmetry of sunspot area

✍ Scribed by C. Sawyer; M. W. Haurwitz

• Publisher: Springer
• Year: 1972
• Tongue: English
• Weight: 419 KB
• Volume: 23
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00148105

✦ Synopsis

Asymmctry of sunspot arca with respect to the central meridian is found to depend strongly on the location of the spot group in its chromospheric fact.la or plage. The usual area excess for spots in the castern half of thc disk is reversed for the relatively rarc spot grottps situated in the following part of the plage. Qualitatively, the observed asynamctries can be explained by supposing that the apparent arca of the spot is decreased by overlying bright facula, especially west of central meridian where the spot (in the usual prcccding position) is viewed through the relatively bright and extensive follower part of the plagc. However, thc variation with central meridian distance of the mean area of spots and of faculae demands a more complex model, in which the spatial distribution of facula and plage also dcpcnds on the location of thc spot group. Since both faeula and spot effects are seen along the same line of sight, optical depth must change slowly with geometric depth, that is, in the active region the atmosphere is relatively transparent.