Soviet-French joint study of the solar corona. III - The structure and certain dynamic features of the corona of June 30, 1973

The overall, as well as the detailed and fine, structure of the corona extending to approximately 3.0-4.0 solar radii is studied. The structure is compared with formations on the solar surface, and certain changes in the structure are traced for periods of 80-90 min. The structure of the rays in the outer corona is studied out to 12 solar radii by reproducing computer-enhanced negatives from a short-focus camera. New phenomena are detected, namely, quasi-continuous dynamic disturbances occurring in and near coronal holes (rifts); they appear to be hydromagnetic in the same way as coronal transients. Data are obtained on the fine-filament structure of the corona, on the relationship between this structure and the magnetic fields and current layers, on the spatial arrangement of large helmet-like rays, on the width of the visibility zone, and on the relationship between the overall structure of the corona and the N-S asymmetry of the activity of the 20th cycle.