Flare activity in NOAA8100 and its forecasting aspects Original Research Article

The pre-flare build-up process of the X9.4/2B flare in NOAA8100 is examined using H α, white-light sunspot, vector magnetogram and soft X-ray images. A 3D extrapolation code is used to infer the coronal magnetic field from observed magnetic field. A magnetic interface of interacting bipoles is clearly identified, and its day by day change is tracked. Two X class flares occurred at the magnetic interface. Furthermore, we found that changes of overlying coronal loop structure and persistence of magnetic interface are strongly related to flare productivity. These results suggest that daily inspection of three dimensional structures of active regions should be useful for operational forecasting.