A study of the background corona near solar minimum

✍ Scribed by Kuniji Saito; Arthur I. Poland; Richard H. Munro

• Publisher: Springer
• Year: 1977
• Tongue: English
• Weight: 868 KB
• Volume: 55
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00150879

✦ Synopsis

The white light coronagraph data from Skylab is used to investigate the equatorial and polar K and F coronal components during the declining phase of the solar cycle near solar minimum. Measurements of coronal brightness and polarization brightness product between 2.5 and 5.5R.) during the period of observation (May 1973 to February 1974) lead to the conclusions that: (1) the equatorial corona is dominated by either streamers or coronal holes seen in projections on the limb approximately 50% and 30% of the time, respectively; (2) despite the domination by streamers and holes, two periods of time were found which were free from the influences of streamers or holes (neither streamers nor holes were within 30 ~ in longitude of the limb); (3) the derived equatorial background density model is less than 15% below the minimum equatorial models of Newkirk (1967) and Saito (1970); (4) a spherically symmetric density model for equatorial coronal holes yields densities one half those of the background density model; and (5) the inferred brightness of the F-corona is constant to within + 10% and +5% for the equatorial and polar values, respectively, over the observation period. While the F-corona is symmetric at 2Ro it begins to show increasing asymmetry beyond this radius such that at 5Ro the equatorial F-coronal brightness is 25% greater than the polar brightness.