Abstract
The goal of this study is to improve our knowledge of the spatial relation between pre-flare and flare X-ray sources, to find other connections between the two phenomena (if they exist) and to study the role of pre-flare heating in flare build-up. We selected all flares with available preflare data observed by Yohkoh during the period October 1993–October 1994 and thus created a data base of 32 flares. When studying the spatial relation we discovered that our events can be classified into 3 categories: Co-spatial, Adjacent/Overlapping and Distant according to the spatial separation between the pre-flare and flare source(s) in the same field of view. The 'Co-spatial’ class of events, of which we found 8 cases, refers to flares that had a visible pre-flare soft X-ray structure with the same size, shape, and orientation as the main flare loops at the flare site at least 5 min before the start of the impulsive phase. We suggest that this is strong evidence that for a significant number of flares the flare structure is active in soft X-rays several minutes or more before the flare begins. However, an analysis of the physical properties of the flare sites, including temperature and intensity variation found no consistent feature distinguishable from other non-flaring active region emission and hence no definite evidence of a special 'pre-flare’ or 'precursor’ phase in solar flares.
Similar content being viewed by others
References
Bumba, V. and Křivský, L.: 1959, Bull. Astron. Inst. Czech. 10, 221.
Fárník, F., Hudson, H., and Watanabe, T.: 1996, Solar Phys. 165, 169.
Martres, M. J.: 1989, Solar Phys. 119, 357.
Kai, K., Nakajima, H., and Kosugi, T.: 1983, Publ. Astron. Soc. Japan 35, 285.
Newton, E. K.: 1997, Astrophys. J. 484, 455.
Plunkett, S. P. and Simnett, G. M.: 1994, Solar Phys. 155, 351.
Schmahl, E. J., Webb, D. F., Woodgate, B., Waggett, P., Bentley, R., Hurford, G., Schadee, A., Schrijver, J., Harrison, R. A., and Martens, P.: 1989, in M. R. Kundu, B. Woodgate, and E. J. Schmahl (eds.), Energetic Phenomena on the Sun, Kluwer Academic Publishers, Dordrecht, Holland, p. 77.
Tsuneta, S., Acton, L., Bruner, M., Lemen, J., Brown, W., Caravalho, R., Catura, R., Freeland, S., Jurcevich, B., and Morrison, M.: 1991, Solar Phys. 136, 37.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Fárník, F., Savy, S. Soft X-Ray Pre-Flare Emission Studied in Yohkoh-SXT Images. Solar Physics 183, 339–357 (1998). https://doi.org/10.1023/A:1005092927592
Issue Date:
DOI: https://doi.org/10.1023/A:1005092927592