Characteristics of Yohkoh X-ray flares and charge states of SEP Fe ions Original Research Article

We study characteristics of the Yohkoh X-ray flares and the ACE/SEPICA charge states of SEP Fe ions for two types of solar events. (1) The 1998 September 9 event was an impulsive hard X-ray flare and CME was not observed. The SEP data showed a low flux with short duration and the mean charge of Fe ions 〈Q〉 was 17.4+/−0.8 at 0.18–0.44 MeV/n. It indicates the characteristics of a flare-associated impulsive SEP event. (2) The 1997 November 6 event emitted intense gamma rays impulsively and strong CME was measured. The SEP observations showed a significantly high flux with a long duration and hard energy spectra. The charge distribution of Fe ions peaks at 11.0+/−0.4 with a tail extending to about 20 at 0.18–0.26 MeV/n. This event seems to exhibit both characteristics of CME-related gradual and flare-related impulsive SEP events. We discuss potential implications of X-ray flares, plasma tempratures and SEP acceleration processes on the basis of Yohkoh and ACE/SEPICA observations.