MAGNETIC TOPOLOGY IN 1998 NOVEMBER 5 TWO-RIBBON FLARE AS INFERRED FROM GROUND-BASED OBSERVATIONS AND LINEAR FORCE-FREE FIELD MODELING

We analyzed the three-dimensional structure of the linear force-free magnetic —eld. A longitudinal magnetogram of Active Region NOAA 8375 has been used as the photospheric boundary condition. The 1998 November 5 2B/M8.4 two-ribbon —are can be explained in the framework of quadrupolar recon- nection theory: the interaction of two closed magnetic loops that have a small spatial angle. The energy derived from soft X-ray telescope (SXT)/Y ohkoh data (3¨6 ) 1030 ergs) is 1 order of magnitude higher than the lower limit of —are energy predicted by Melroses model. The latter estimation was made using the linear force-free extrapolation. It was suggested that, taking into account the nonlinear character of the observed magnetic —eld, we can increase the lower limit of the magnetic energy stored in the studied magnetic con—guration. The revealed magnetic con—guration allows us to understand the observed loca- tion and evolution of the —are ribbons and the additional energy released during the gradual phase of the —are, as well. Besides, reconnection of closed magnetic loops can logically explain the connection between a two-ribbon —are and a giant X-ray post—are arch, which usually is observed after the —are onset. We emphasize that unlike the Kopp and Pneuman con—guration, the model discussed here does not necessarily require destabilization and opening of the magnetic —eld. Subject headings: Sun: —aresSun: magnetic —elds