Long-decay soft X-ray flares. 2

Of the total number of 106 flares which originated in two closely spaced regions, Hale 17 901 and 17 906 between Oct. 7 and 14, 1981, 27 are analyzed with regard to H-alpha, SXR (soft X-radiation) and HXR (hard X-radiation) emissions. The flares of importance 1 N which originated between Oct. 9 and 11, 1981 showed weak X-ray emissions. On Oct. 12, three strong X-ray flares originated (04:38, 06:15 and 10:33 UT). The detailed analysis of the three-ribbon LDE (long distance event) flare of Oct. 12, 06:15 UT showed that the flare had two impulsive HXR phases (06:20 and 07:29 UT). In the course of the second impulsive phase, the dark post-flare loops vanished and the third central ribbon became more distinct. The third central H-alpha ribbon can be interpreted as radiation which is generated in the hot loop tops, however, the loops were located in the bottom part of the arcade, lower down than the dark post-flare loops. No filament was observed in this LDE flare. The values of the effective color temperature and the emission measure of 22 flares were computed using the method of two-color SXR photometry. The quasisynchronousness of the origin of flare pairs was proved in 4 cases. (author) 13 figs., 4 tabs., 67 refs