Magnetic flux cancellation associated with the major solar event on 2000 July 14

The major solar event on 2000 July 14 is characterized by the simultaneous occurrence of a giant filament eruption, a great flare, and an extended Earth-directed coronal mass ejection. We examined in detail the magnetic evolution in its source active region, NOAA 9077, and found that the only obvious magnetic change in the course of the event is magnetic flux cancellation at many sites in the vicinity of the filament. Moreover, all the initial disturbance in the filament and the initial brightening around the filament took place at the cancellation sites. It is clearly indicated that the slow magnetic reconnection in the lower atmosphere, which is manifested as observed flux cancellation, is of overwhelming importance in leading to the global instability responsible for the major magnetic activity.