Relationship between electric currents,photospheric motions,chromospheric activity,and magnetic field topology |
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| Authors: | L van Driel-Gesztelyi A Hofmann P Démoulin B Schmieder G Csepura |
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| Institution: | (1) Astronomical Institute, University of Utrecht, 3508 TA Utrecht, The Netherlands;(2) Kiso Observatory, Institute of Astronomy, University of Tokyo, 397-01 Mitake-mura, Kiso-gun, Nagano-ken, Japan;(3) Astrophysikaliches Institut Potsdam, Sonnenobservatorium Einsteinturm, D.O.-1561 Potsdam, Telegrafenberg, Germany;(4) Observatoire de Paris, DASOP, URA 326, CNRS, 92195 Meudon Cédex, France;(5) Heliophysical Observatory of the Hungarian Academy of Sciences, H-4010 Debrecen, Hungary |
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| Abstract: | Through coordinated observations made during the Max'91 campaign in June 1989 in Potsdam (magnetograms), Debrecen (white light and H ), and Meudon (MSDP), we follow the evolution of the sunspot group in active region NOAA 5555 for 6 days. The topology of the coronal magnetic field is investigated by using a method based on the concept of separatrices - applied previously (Mandriniet al., 1991) to a magnetic region slightly distorted by field-aligned currents. The present active region differs by having significant magnetic shear. We find that the H flare kernels and the main photospheric electric current cells are located close to the intersection of the separatrices with the chromosphere, in a linear force-free field configuration adapted to the observed 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 idea that flares are due to magnetic reconnection, when flux tubes with field-aligned currents move towards the separatrix locations. |
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