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Solar Physics

, Volume 136, Issue 1, pp 133–149 | Cite as

Studies on a very flare-active δ group: Peculiar δ spot evolution and inferred subsurface magnetic rope structure

  • Katsuo Tanaka
Article

Abstract

The complex subsurface magnetic rope structure of a very flare-active isolated δ group (McMath 13043, July 1974) is studied by means of high-resolution evolutionary data from BBSO magnetic and velocity data. This group showed unusually fast evolution accompanied by a number of intense flares occurring on the neutral line of a δ spot, and provided an excellent opportunity to study the inherent relation of flare occurrence to changes of the magnetic configuration. We first examine the abnormal evolution of this group started by formation of a large, compact, reversed δ spot by squeezing of multipoles. The δ configuration was deformed by penetration into the opposite polarity umbra and its subsequent disappearance, decaying by rapid shear motions. Strong transverse fields over 4000 G were detected in the penumbrae and some umbral components.

Combining these data with the August 1972 region, the evolution of these isolated δ groups is shown to decompose into two flare-associated elementary modes: (A) shearing produced by spot growth and (B) reduction of shear as spots disappear. We propose a model of an emerging twisted magnetic knot to explain the two modes and apply realistically to the present evolution. The inferred magnetic topological structure of this region consists of tightly twisted (sheet-like) knots and a long-winding twisted rope with an internally reversed loop and a hooked bottom struture. Their consecutive emergences are suggested to explain the abnormal evolution of this 5 group. This result indicates that the origin of the concentrated flare activity in these isolated δ groups may be traced to internal magnetic activity responsible for forming anomalous magnetic ropes.

Keywords

Flare Neutral Line Abnormal Evolution Flare Activity Strong Transverse 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Bruzek, A.: 1960, Z. Astrophys. 50, 110.Google Scholar
  2. Bruzek, A.: 1967, Solar Phys. 2, 451.Google Scholar
  3. Ellison, M. A., McKenna, S. M. P. and Reid, J. H.: 1960, Observatory 80, 149.Google Scholar
  4. Hagyard, M. J., Smith, J. B., Teuber, D., and West, E. A.: 1984, Solar Phys. 91, 115.Google Scholar
  5. Kunzel, H.: 1960, Astron. Nachr. 285, 271.Google Scholar
  6. Livingston, W.: 1974, Proc. Flare-Related Magnetic Field Dynamics, Conference in Boulder, HAO-NCAR, p. 269.Google Scholar
  7. McIntosh, P.: 1969, World Data Center A, Rep. UAG-5, p. 14.Google Scholar
  8. McIntosh, P.: 1970, World Data Center A, Rep. UAG-5, p. 22.Google Scholar
  9. Sakurai, K.: 1972, Solar Phys. 23, 142.Google Scholar
  10. Sawyer, C. and Smith, S.: 1970, World Data Center A, Rep. UAG-9, p. 9.Google Scholar
  11. Tanaka, K.: 1980, in R. F. Donnelly (ed.), Solar-Terrestrial Predictions Proceedings, NOAA-ERL, 3, C1.Google Scholar
  12. Tang, F.: 1983, Solar Phys. 89, 43.Google Scholar
  13. Warwick, C.: 1966, Astrophys. J. 145, 215.Google Scholar
  14. Zirin, H.: 1988, Astrophysics of the Sun, Cambridge University Press, Cambridge, p. 321.Google Scholar
  15. Zirin, H. and Liggett, M. A.: 1987, Solar Phys. 113, 267.Google Scholar
  16. Zirin, H. and Tanaka, K.: 1973, Solar Phys. 32, 173.Google Scholar

Copyright information

© Kluwer Academic Publishers 1991

Authors and Affiliations

  • Katsuo Tanaka
    • 1
    • 2
  1. 1.Big Bear Solar Observatory, California Institute of TechnologyPasadenaU.S.A.
  2. 2.National Astronomical Observatory MitakaTokyoJapan

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