EVIDENCE OF MAGNETIC RECONNECTION FROM H-ALPHA, SOFT-X-RAY AND PHOTOSPHERIC MAGNETIC-FIELD OBSERVATIONS

A conventional view of magnetic reconnection is mainly based on the 2- D picture of an X-type neutral point, or on the extension of it to 3-D , and it is thought to be accompanied by flux transport across separat rices (places where the field-line mapping is discontinuous). This vie w is too restrictive when we realize the variety of configurations tha t are seen flaring. We designed an algorithm, called Source Method (SM ), to determine the magnetic topology of active regions (ARs). The obs erved photospheric field was extrapolated to the corona using subphoto spheric sources and the topology was defined by the link between these sources. Her flare brightenings were found to be located at the inter section with the chromosphere of the separatrices so defined. These re sults and the knowledge we gained on the properties of magnetic held-l ine linkage, led us to generalize the concept of separatrices to 'quas i-separatrix layers' (QSLs) and to design a new method ('quasi-separat rix layers method', QSLM) to determine the magnetic topology of ARs. Q SLs are regions where the magnetic field-line linkage changes drastica lly (discontinuously when they behave like separatrices) and the QSLM can be applied to ARs where the photospheric held has been extrapolate d using any kind of technique. In this paper we apply the QSLM to obse rved flaring regions presenting very different configurations and also to a decaying AR where a minor phenomenon, like an X-ray bright point (XBP), is observed. We find that the locations of flare and XBP brigh tenings are related to the properties of the field-line linkage of the underlying magnetic region, as expected from recent developments of 3 -D magnetic reconnection. The extrapolated coronal field lines represe nting the structures involved in the analyzed events have their photos pheric footpoints located at both sides of QSLs. Our results strongly support the hypothesis that magnetic reconnection is at work in variou s coronal phenomena, ranging from the less energetic ones to large sca le eruptions.