Active Magnetic Interfaces and Flares in Noaa 7469

Time sequences of vector magnetograms and H filtergrams of NOAA 7469 were obtained during 4–12 April 1993 at Huairou Solar Observing Station of Beijing Astronomical Observatory. The region was characterized by the emergence of several new bipoles and the formation of active magnetic interfaces between newly emerging and pre-existing magnetic flux. Based on the 3-D magnetic lines of force, computed with the boundary element method (BEM), it has been found that the topology of magnetic lines of force changes when longitudinal magnetic fields evolve during the observing period. Two active magnetic interfaces were identified from 6 to 8 April in this region. By comparing H filtergrams with vector magnetograms of the photosphere and 3-D magnetic lines of force, it is found that many flares initiated at the active magnetic interfaces.