A 3B Flare of 1989 April 9

A 3B flare which occurred in a spotless region on April 9, 1989, is morphologically analysed. The main results arc thcwn as follows. 1. The flare has the two-ribbon structure, and the active filaments arc surrounded by the two ribbons. 2. There are obvious changes in the S-shaped active filaments relevant with the flare before and after the flare eruption, and all of the filaments disappear at last. 3. The X-ray events of the flare cause a class-one SID and a class-two SID, respectively. 4. The off-band obecrvations show that there exists the descending motion of material during the eruption of the flare. 5. There is the spiral structure in the sunspot penumbra.