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Astron. Astrophys. 342, 854-862 (1999)

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Two-dimensional singular points in an observed transverse field in solar active region NOAA 7321

Wang Tongjiang 1, Wang Huaning 1 and Qiu Jiong 2

1 Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100012, P.R. China (e-mail: wtj@sun10.bao.ac.cn)
2 Department of Astronomy, Nanjing University, Nanjing 210093, P.R. China

Received 14 March 1997 / Accepted 20 November 1998


In the present paper, we give a realistic diagnosis to 2D singular points in the observed transverse field in AR 7321 on October 27, 1991. These singular points are compared with those in the extrapolated field, inferred from the observed longitudinal field boundary on a linear force-free field model. The extrapolated 3D magnetic connectivity patterns are taken to determine the involved separatrices. In order to understand the heating mechanism of flaring loops in the corona, we compare singular features in the photosphere with SXR observations from Yohkoh. The major results include: (a) The filtering technique is proven efficient in excluding the false candidate points due to the measurement noise. (b) The 2D topology of the observed field indicates more interesting characters than those the linear force-free field can interpret, which are involved in the evolution of magnetic structures. (c) Two kinds of 2D cells, differed by 2D magnetic connectivity patterns, are associated with magnetic loops of different heights and shapes. (d) Some events releasing energy show that coronal loops are interacting at regions, which are involved in the separatrices.

Key words: Sun: activity – Sun: flares – Sun: magnetic fields – Sun: X-rays, gamma rays

Send offprint requests to: T. Wang

© European Southern Observatory (ESO) 1999

Online publication: February 23, 1999