ON ACTIVATION OF TWO ARCH-LIKE FILAMENTS 0F FEBRUARY 4, 1986

Using observational data, the images in Ha and white light and the vector magnctogram, the dynamical behaviour of two arch-like filaments in AR47/11 on February 4, l986 before the eruption of a 3B /X3 flare is analytal numerically. It Ieads to the following condusions (l) the rotating motion nearby the footpoints of the filament system and shearing motion in the neighbourhood of the neutral line play an irnportant role in driving upward motion of the filament system. The ascending velocity of the filament can be up to 26 km /s before the flare beginning; (2) the dynamical behaviour of the filament system is influened by the background field medel. The deay of the magneti fiekl along with the hdght is exponenhal in AR4711.