AN INVESTIGATION OF THE LARGE-SCALE MAGNETIC-FIELD VARIATIONS IN THE CORONA PRIOR TO AND AFTER CME ERUPTIONS

The magnetic field changes in the corona at the site of coronal mass e jections (CMEs) have been investigated using the potential field-soure r surface model. It is shown that a CME is accompanied by the opening of closed field lines that formed the streamer's helmet base prior to the onset of a coronal disturbance. Two to three days after the appear ance of the CME, the field configuration at the location of the corona l ejection reverts approximately to the state pre-existing before the generation of the CME. The appearance of small transient open magnetic tubes has been found after eruption of the coronal mass. These magnet ic tubes seem to be the analogs for transient coronal holes. Taking in to account the results of calculations of the field changes in the nei ghbourhood of the CME occurrence site, we have suggested a possible me chanism governing the spatio-temporal correlation between some flares and CMEs. Also, a possible mechanism has been proposed for field recon figuration in the corona, leading to loss of the equilibrium of the ma gnetic configuration and to the subsequent generation of a CME in the region of coronal streamer chains separating coronal holes with same-p olarity magnetic field.