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

Very faint Hα emission in the solar corona registered on over-exposed photographs made by a coronagraph and an Hα 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 Hα 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 Hα emission is proposed.