Coronal photometry and analysis of the eclipse corona of July 22, 1990

Abstract : An extensive collaborative study of the maximum-type solar corona at the July 22, 1990 eclipse has been performed after collecting data from the ground and from an aircraft. The study provides photometric quality data and structural analysis on the electron corona. Synoptic data are used from the Emission-Line Coronal Photometer of the National Solar Observatory/Sacramento Peak. The activity of the low corona at the time of the eclipse is first discussed. Noticeable is a large nearby polar hole at the SSW limb well-observed on both synoptic green-line data and eclipse data. Strong activity is seen at the E and W limbs and numerous faint prominences are recorded all around the limb. The photometry of the White-Light corona has been performed with selected pictures from the French Falcon-20 aircraft experiment flown above Finland. Isophote maps are given as well as azimuthal scans in absolute units of average solar brightness. The standard flattening index is computed using the values determined for different radial distances. A few scans are compared with Fe XIV 530.3nm scans, and show great similarity when prominence emissions are excluded. The structural analysis is based on the excellent radially-filtered eclipse pictures obtained from the ground with one of the standard multi-station experiments placed along the path of totality in the USSR. Both the inner parts and especially the outer parts of the plasma corona are analyzed.