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Astron. Astrophys. 357, 725-734 (2000)

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Soft X-ray flares and magnetic configuration in a solar active region in February 1992

H.Q. Zhang 1, T. Sakurai 2, K. Shibata 2, M. Shimojo 2 and H. Kurokawa 3

1 Beijing Astronomical Observatory, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, P.R. China
2 National Astronomical Observatory, Mitaka, Tokyo 181, Japan
3 Kwasan and Hida Observatories, Kyoto University, Kyoto 606, Japan

Received 4 August 1999 / Accepted 13 December 1999


In this paper, we examine the observational soft X-ray flares and the relationship with photospheric vector magnetograms in the active region (NOAA 7070). We analyze the soft X-ray flare on Feb. 24-25, 1992, especially the pre-flare and the relationship with the highly sheared photospheric vector magnetic field near the photospheric magnetic neutral line.

We find that the initial reconnection of the magnetic field in the flare on Feb. 24-25, 1992 probably occurs near the magnetic neutral line in the lower atmosphere of the active region, where the highly sheared magnetic flux erupts up and triggers the reconnection of the large-scale magnetic field. The possible process of the magnetic reconnection of the limb flare on Feb. 20-21, 1992 in this active region is proposed also based on the analogy with the flare on Feb. 24-25 near the center of the solar disk.

Key words: sun: activity – sun: flare – sun: magnetic fields

Send offprint requests to: H.Q. Zhang

Correspondence to: zhq@sun10.bao.ac.cn

© European Southern Observatory (ESO) 2000

Online publication: June 5, 2000