A Statistical Analysis of Faint Hα Coronal Emission Associated with Prominences

The results from a detailed study of the prominences associated with faint H emission objects in the solar corona are given. The frequency distribution of the prominences by their lifetime, as well as for the prominence groups with and without `disparition brusque' (DB), is presented. The systematic comparison of the time of the prominence DBs and the observation time of the objects with faint H emission, as well as the positions of the faint H emissions and the associated filaments at the limb and on the disk of the Sun, suggests that in the most cases these coronal emissions are probably closely connected with the instability processes operating in the prominence magnetic field configurations and leading to prominence final or temporary DBs.     

An Estimation of the Long-Term Variation of a North–South Asymmetry of the Long-Lived Solar Filaments

The present paper estimates the long-term variation of the north-south asymmetry of long-lived solar filaments from Meudon's catalogues during the period 1919–1989. A long-time period of the filament asymmetry variation of about 11 solar cycles was found by using the cumulative index for the filament north-south asymmetry. This estimation is very close to the long-time variation period of the north-south asymmetry of solar activity obtained by means of a spectral analysis.     

Periodicities in the N-S asymmetry of long-lived solar filaments

The N-S asymmetry of the long-lived solar filaments published in the Meudon catalogues for the time interval 1919–1989 is studied by means of power-spectrum analysis. Statistically significant periods of 35.0 and 11.7 yr are obtained. There are no statistically significant periods shorter than 11 yr.     

Faint Hα emission in the solar corona: Morphological,situational and hydromagnetic analysis

Very faint H emission in the solar corona registered on over-exposed photographs made by a coronagraph and an H filter is studied. The over-exposed filtergrams have been processed by a Joyce Loebl automated microdensitometer and the two-dimensional scans have been analysed by the residual image method. A classification of the faint H emission objects, revealed on the isodensity maps, is proposed and the latitudinal distribution, the morphology, and the location with respect to the other active phenomena are analysed. Taking into account some possible plasma effects that could be caused by coronal magnetic field changes, a hydromagnetic interpretation of the faint H emission is proposed.