Solar Physics

, Volume 170, Issue 2, pp 411–423 | Cite as

AN ‘EXTENDED SOLAR CYCLE’ AS OBSERVED IN Fe XIV

  • Richard C. Altrock
Article

Abstract

Investigation of the behavior of coronal intensity above the limb in Fexiv emission (530.3 nm) obtained at the National Solar Observatory at Sacramento Peak over the last 23 years has resulted in the confirmation of a second set of zones of solar activity at high latitudes, separate from the Main Activity Zones (MAZ). Localized high-latitude intensity maxima, which I will call High-latitude Emission Features (HEF), are observed at 0.15 solar radii above the limb throughout the solar cycle. They persist long enough at a given latitude to be visible in long-term (e.g., annual) averages. I identify two types of HEF. Poleward-moving HEF, which may be identified with the ‘Rush to the Poles’ phenomenon seen in polar-crown prominences, were first seen to appear in this investigation near latitude 60° in 1978. In 1979 equatorward-moving HEF branched off from the poleward-moving HEF (which continued on to reach the pole in 1980) at a latitude of 70° to 80°. They evolved approximately parallel to the MAZ. Near solar minimum, these HEF evolved into the MAZ of cycle 22, and the emission continues its path towards the equator, where it should disappear soon.

Currently, it is clear that the pattern seen earlier is repeating. The poleward-moving HEF became apparent near the beginning of 1988 near 50° to 60° latitude. The northern poleward-moving HEF reached the pole and disappeared in 1990. The southern poleward-moving HEF moved more slowly, reaching the pole and disappearing in 1991. The equatorward-moving HEF that are the precursors of cycle 23 appeared in 1989 to 1990 and began to move approximately parallel to the MAZ of cycle 22. Based on inferences from previous cycles, we can expect these HEF to continue to the equator, with emission ceasing there near 2009. These recent observations increase the evidence for an ‘extended’ solar cycle that begins every 11 years but lasts for approximately 19–20 years.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Altrock, R. C. (ed.): 1988, Solar and Stellar Coronal Structure and Dynamics: a Festschrift in Honor of Dr John W. Evans, Proceedings of the Ninth Sacramento Peak Summer Symposium, Sunspot, NM, 17–21 August, 1987, p. 414.Google Scholar
  2. Altrock, R. C.: 1992, Bull. Am. Astron. Soc. 24, 746.Google Scholar
  3. Babcock, H. W.: 1961, Astrophys. J. 133, 572.Google Scholar
  4. Bumba, V., Rušin, V., and Rybanský, M.: 1990, Bull. Astron. Inst. Czech. 41, 253.Google Scholar
  5. Fisher, R. R.: 1973, A Photoelectric Photometer for the FeXIV Solar Corona, Rep. AFCRL-TR-73– 0696, Air Force Geophysics Laboratory, Hanscom AFB,MA. Available from National Technical Information Service, Publication Number ADA 775745.Google Scholar
  6. Fisher, R. R.: 1982, Astrophys. J. 259, 431.Google Scholar
  7. Giovanelli, R. G.: 1985, Australian J. Phys. 38, 1045.Google Scholar
  8. Hansen, R. T., Garcia, C. J., Hansen, S. F., and Loomis, H. G.: 1969, Solar Phys. 7, 417.Google Scholar
  9. Hara, H.: 1996, ‘Structures and Heating Mechanisms of the Solar Corona’, Ph.D. Thesis, University of Tokyo, Chapter 9, p. 151.Google Scholar
  10. LaBonte, B. J. and Howard, R.: 1982, Solar Phys. 75, 161.Google Scholar
  11. Martin, S. F. and Harvey, K. L.: 1979, Solar Phys. 64, 93.Google Scholar
  12. Minarovjech, M., Rybanský, M., and Rušin, V.: 1996, in J. Pap (ed.), SOLERS22, Proceedings of the Workshop on the Solar Electromagnetic Radiation Study for Solar Cycle 22: Sunspot, NM, June, 1996 (submitted).Google Scholar
  13. Sime, D. G., Fisher, R. R., and Altrock, R. C.: 1985, Solar Coronal White Light, Fe X, Fe XIV, and Ca XV Observations during 1984: An Atlas of Synoptic Charts, National Center for Atmospheric Research Technical Note No. TN-251+STR.Google Scholar
  14. Smartt, R. N.: 1982, Proc. SPIE 331, 442.Google Scholar
  15. Snodgrass, H. B. and Howard, R. F.: 1985, Science 228, 945.Google Scholar
  16. Stenflo, J. O.: 1988, Astrophys. Space Sci. 144, 321.Google Scholar
  17. Stenflo, J. O.: 1992, in K. L. Harvey (ed.), The Solar Cycle: Workshop Proceedings, National Solar Observatory at Sacramento Peak (12th), 15–18 October, 1991. (Astronomical Society of the Pacific), p. 421.Google Scholar
  18. Sýkora, J.: 1980, in M. Dryer and E. Tandberg-Hanssen (eds.), ‘Solar and Interplanetary Dynamics’, IAU Symp. 91, 87.Google Scholar
  19. Wilson, P. R., Altrock, R. C., Harvey, K. L., Martin, S. F., and Snodgrass, H. B.: 1988, Nature 333, 748.Google Scholar
  20. Yoshimura, H.: 1981, Astrophys. J. 247, 1102.Google Scholar

Copyright information

© Kluwer Academic Publishers 1997

Authors and Affiliations

  • Richard C. Altrock
    • 1
  1. 1.Phillips Laboratory (AFMC), Geophysics DirectorateNational Solar Observatory/Sacramento PeakUSA

Personalised recommendations