The intensity, velocity and magnetic structure of a sunspot region

✍ Scribed by J. M. Beckers; E. H. Schröter

• Publisher: Springer
• Year: 1968
• Tongue: English
• Weight: 783 KB
• Volume: 4
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00149561

✦ Synopsis

A time sequence of high-resolution sunspot photographs, exposed almost simultaneously in two continuum wavelengths (4680/~ and 6400 ~), was used to study some properties of umbral fine structures ('umbral dots'). The lifetime of the umbral dots is found to be 1500 sec. Photometry of some bright dots leads to an observed intensity excess of 0.129 lvhot and 0.134 Ip~aot in the blue and red respectively. The observed mean diameter of the dots is found to be 420 kin. These values still include the action of image blurring. From the color index the true intensity and diameter of the dots are estimated. It appears that the umbral dots are in reality of photospheric brightness having true diameters of 150-200 kin. The spatial distribution of the dots in sunspot umbrae is discussed. Some peculiarities in recent sunspot magnetic-field observations may be explained by magnetic inhomogeneities associated with umbral dots. * Presently guest investigator at the G6ttingen Observatory. ** Previously member of the High Altitude Observatory solar project at Sacramento Peak (Contract Nr. AF (628) -4078).