RELATIONSHIP BETWEEN ELECTRIC CURRENTS, PHOTOSPHERIC MOTIONS, CHROMOSPHERIC ACTIVITY, AND MAGNETIC-FIELD TOPOLOGY

Through coordinated observations made during the Max'91 campaign in Ju ne 1989 in Potsdam (magnetograms), Debrecen (white light and Halpha), and Meudon (MSDP), we follow the evolution of the sunspot group in act ive region NOAA 5555 for 6 days. The topology of the coronal magnetic field is investigated by using a method based on the concept of separa trices - applied previously (Mandrini et al., 1991) to a magnetic regi on slightly distorted by field-aligned currents. The present active re gion differs by having significant magnetic shear. We find that the Ha lpha flare kernels and the main photospheric electric current cells ar e located close to the intersection of the separatrices with the chrom osphere, in a linear force-free field configuration adapted to the obs erved shear. Sunspot motions, strong currents, isolated polarities, or intersecting separatrices are not in themselves sufficient to produce a flare. A combination of them all is required. This supports the ide a that flares are due to magnetic reconnection, when flux tubes with f ield-aligned currents move towards the separatrix locations.