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.
Xuan Jiayu, Luo Zhi, Ye Huilian, Lin Jun, Zhong Shuhua, Chen Xuekun, Li Jiukang. AR5629:A LARGE LOOP-SHAPE FLAREON 17 AUG.1989
[J]. Publications of the Yunnan Observatory, 1990, 0(4): 181-184.