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Solar Physics

, Volume 214, Issue 1, pp 65–87 | Cite as

Measurement of Kodaikanal white-light images – VI. Variation of Rotation Rate with Age of Sunspot Groups

  • K.R. Sivaraman
  • Hari Sivaraman
  • S.S. Gupta
  • Robert F. Howard
Article

Abstract

We find from an analysis of the Kodaikanal sunspot group data that the rotation rates of spot groups increase with their age when the rotation rates are computed after sorting the spot groups life-span-wise. We confirm these findings from an analysis of the Mt. Wilson sunspot data set too. We show that this trend is in good agreement with the internal rotation profiles from helioseismology (GONG) observations and is also consistent with the concept that the footpoints of the magnetic loops of spot groups are initially anchored in the deeper layers in the solar interior and rise to shallower layers as the spots age, and that the spots reflect the rotation rates at the respective depths at which their footpoints are temporally located. We project the `first-day rotation rates' and the `daily rotation rates' of spot groups on the rotation profiles from the GONG observations and derive the initial anchoring depths of the footpoints of the magnetic loops of the spot groups and their rates of rise as the spot groups age. Our results of the rotation rates are in antithesis to the results reported by investigators from the Greenwich spot group data that show a deceleration in rotation rates as the spot groups age which are also inconsistent with the rotation profiles from helioseismology observations.

Keywords

Internal Rotation Rotation Rate Group Data Sunspot Group Magnetic Loop 
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. Balthasar, H., Vázquez, M., and Wöhl, H.: 1986, Astron. Astrophys. 155, 87.Google Scholar
  2. Beck, J. G.: 1999, Solar Phys. 191, 47.Google Scholar
  3. Gilman, P. A and Foukal, P. V.: 1979, Astrophys. J. 229, 1179.Google Scholar
  4. Gupta, S. S., Sivaraman, K. R., and Howard, R. F.: 1999, Solar Phys. 188, 225 (Paper III).Google Scholar
  5. Harvey, K. and Harvey, J.: 1973, Solar Phys. 28, 61.Google Scholar
  6. Hiremath, K. M.: 2002, Astron. Astrophys. 386, 674.Google Scholar
  7. Howard, R. F., Gilman, P. A., and Gilman, P. I.: 1984, Astrophys. J. 283, 373 (HGG).Google Scholar
  8. Howard, R. F., Gupta, S. S., and Sivaraman, K. R.: 1999, Solar Phys. 186, 25 (Paper II).Google Scholar
  9. Javaraiah, J.: 2001, Ph.D. Thesis, Bangalore University, India.Google Scholar
  10. Javaraiah, J. and Gokhale, M. H.: 1997, Astron. Astrophys. 327, 795.Google Scholar
  11. Moreno-Insertis, F.: 1994, in M. Schüssler and W. Schmidt (eds.), Solar Magnetic Fields, Cambridge University Press, Cambridge, p. 117.Google Scholar
  12. Schou, J. et al.: 2002, Astrophys. J. 567, 1234.Google Scholar
  13. Schrijver, C. J. and Zwaan, C.: 2000, Solar and Stellar Magnetic Activity, Cambridge Astrophysics Series 34, Cambridge University Press, Cambridge.Google Scholar
  14. Schüssler, M.: 1987, in B. R. Durney and S. Sofia (eds.), The Internal Solar Angular Velocity, D. Reidel Publ. Co., Dordrecht, Holland, p. 303.Google Scholar
  15. Schüssler, M., Caligari, P., Ferriz-Mas, A., and Moreno-Insertis, F.: 1994, Astron. Astrophys. 281, L69.Google Scholar
  16. Sivaraman, K. R., Gupta, S. S., and Howard, R. F.: 1993, Solar Phys. 146, 27 (Paper I).Google Scholar
  17. Tuominen, I. and Virtanen, H.: 1987, in B. R. Durney and S. Sofia (eds.) The Internal Solar Angular Velocity, D. Reidel Publ. Co., Dordrecht, Holland, p. 83.Google Scholar
  18. Vrabec, D.: 1971, in R. Howard (ed.), 'Solar Magnetic Fields', IAU Symp. 43, 329.Google Scholar
  19. Zappala, R. A. and Zuccarello, F.: 1991, Astron. Astrophys. 242, 480.Google Scholar
  20. Zuccarello, F.: 1993, Astron. Astrophys. 272, 587.Google Scholar

Copyright information

© Kluwer Academic Publishers 2003

Authors and Affiliations

  • K.R. Sivaraman
    • 1
  • Hari Sivaraman
    • 2
  • S.S. Gupta
    • 1
  • Robert F. Howard
    • 3
  1. 1.Indian Institute of AstrophysicsBangaloreIndia
  2. 2.San JoseU.S.A
  3. 3.National Solar ObservatoryTucsonU.S.A

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