Abstract
A large delta spot (active region NOAA 6891, October 23 – November 4, 1991) is analysed, and it is found that some spiral filaments across the spot can be regarded as signatures of a singular point entity (SPE) which lies near a separator of this complicated magnetic field region. Near such an entity, 86% of the flares in the region were produced, including two white-light flares, one of which, being the largest flare of the region, was accompanied by a powerful mass ejection. In an island delta spot, a SPE could be recognized very close to the usual U-shaped inversion lines. Together with the other characteristics (bright Hα emission, highly sheared magnetic field, umbra obscured by Hα, magnetic flux imbalance in the range 2∶1–3∶1), the SPE can help us to predict effectively the sites for great flares to occur (Zirin and Liggett, 1987).
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References
Démoulin, P. and Hénoux, J. C.: 1992, Solar Phys. 139, 105.
Démoulin, P., Mandrini, C. H., Rovira, M. G., Hénoux, J. C., and Machado, M. E.: 1994, Solar Phys. 150, 221.
Low, B. C.: 1987, Astrophys. J. 323, 359.
Low, B. C.: 1991, Astrophys. J. 381, 295.
Titov, V. S., Priest, E. R., and Démoulin, P.: 1993, Astron. Astrophys. 276, 564.
Zirin, H. and Liggett, M. A.: 1987, Solar Phys. 113, 267.
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On leaving from Purple Mountain Observatory, Nanjing, China.
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Hu, F.M., Song, M.T., Liu, Q.Z. et al. Spiral filaments — The signature of singular points in a large delta spot. Sol Phys 165, 395–397 (1996). https://doi.org/10.1007/BF00149721
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DOI: https://doi.org/10.1007/BF00149721