Solar Physics

, Volume 113, Issue 1–2, pp 267–283 | Cite as

Delta spots and great flares

  • Harold Zirin
  • Margaret A. Liggett


Using eighteen years of observations at Big Bear, we summarize the development of δ spots and the great flares they produce. We find δ groups to develop in three ways: eruption of a single complex active region formed below the surface, eruption of large satellite spots near (particularly in front of) a large older spot, or collision of spots of opposite polarity from different dipoles. Our sample of twenty-one δ spots shows that once they lock together, they never separate, although rarely an umbra is ejected. The δ spots are already disposed to their final form when they emerge. The driving force for the shear is spot motion, either flux emergence or the forward motion of p spots in an inverted magnetic configuration.

We observe the following phenomena preceding great flares:
  1. 1.

    δ spots, preferentially Types 1 and 2.

  2. 2.

    Umbrae obscured by Hα emission.

  3. 3.

    Bright Hα emission marking flux emergence and reconnection.

  4. 4.

    Greatly sheared magnetic configurations, marked by penumbral and Hα fibrils parallel to the inversion line.


We assert that with adequate spatial resolution one may predict the occurrence of great flares with these indicators.


Flare Fibril Active Region Opposite Polarity Forward Motion 


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  1. Donnelly, R. F., ed.: 1975, Solar-Terrestrial Predictions Proceedings Vol. 3, Cl. NOAA-ERL.Google Scholar
  2. Kunzel, H.: 1960, Astron. Nachr. 285, 271.ADSCrossRefGoogle Scholar
  3. Kunzel, H., Mattig, W., and Schroter, E. H.: 1961, Die Sterne 9/10, 198.Google Scholar
  4. Patterson, A. and Zirin, H.: 1981, Astrophys. J. 243, L99.ADSCrossRefGoogle Scholar
  5. Rust, D. M.: 1968, IAU Symp. 35, 7.Google Scholar
  6. Sawyer, C. S., Warwick, J. W., and Dennett, J. T.: 1986, Solar Flare Prediction, Colorado.Google Scholar
  7. Smith, S. F. and Howard, R. F.: 1968, IAU Symp. 35, 33.ADSGoogle Scholar
  8. Tanaka, K.: 1975, BBSO Preprint No. 0152.Google Scholar
  9. Tanaka, K.: 1980, in R. F. Donelly (ed.), Solar-Terrestrial Predictions Proceedings Vol. 3, Cl. NOAA-ERL.Google Scholar
  10. Tanaka, K. and Zirin, H.: 1985, Astrophys. J. 299, 1036.ADSCrossRefGoogle Scholar
  11. Tang, F.: 1983, Solar Phys. 89, 43.ADSCrossRefGoogle Scholar
  12. Zirin, H.: 1970a, Solar Phys. 14, 328.ADSCrossRefGoogle Scholar
  13. Zirin, H.: 1970b, Solar Phys. 14, 342.ADSCrossRefGoogle Scholar
  14. Zirin, H.: 1983, Astrophys. J. 274, 900.ADSCrossRefGoogle Scholar
  15. Zirin, H. and Tanaka, K.: 1973, Solar Phys. 32, 173.ADSCrossRefGoogle Scholar
  16. Zirin, H. and Tanaka, K.: 1981, Astrophys. J. 250, 791.ADSCrossRefGoogle Scholar
  17. Zirin, H. et al.: 1982, Astrophys. J. 259, 392.ADSCrossRefGoogle Scholar

Copyright information

© D. Reidel Publishing Company 1987

Authors and Affiliations

  • Harold Zirin
    • 1
  • Margaret A. Liggett
    • 1
  1. 1.Big Bear Solar Observatory, California Institute of TechnologyPasadena

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