Spiral filaments — The signature of singular points in a large delta spot
✍ Scribed by F. M. Hu; M. T. Song; Q. Z. Liu; H. S. Ji
- Publisher
- Springer
- Year
- 1996
- Tongue
- English
- Weight
- 535 KB
- Volume
- 165
- Category
- Article
- ISSN
- 0038-0938
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✦ Synopsis
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 Hce emission, highly sheared magnetic field, umbra obscured by Hoe, 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).