Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

A 154-day periodicity in the occurrence of hard solar flares?


Since the launch of the Solar Maximum Mission (SMM) satellite on 1980 February 14, the Gamma-Ray Spectrometer (GRS)1 has been monitoring the Sun in the energy range 0.3–100 MeV. Because of its large geometric area and good spectral resolution, the GRS has provided unprecedented spectral and temporal information about solar flares, of which 139 have been monitored. We report here on an analysis of the temporal distribution of these high-energy events to provide information on solar activity and find that, instead of being randomly distributed in time, these events have a tendency to occur in groups with a mean spacing of 154 days (75 nHz) over the observing interval. A larger sample of flares (>500), with an X-ray classification of ≥M 2.5 recorded by the GOES satellites, showed a similar regularity.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout


  1. Forrest, D. J. et al. Solar Phys. 65, 15–23 (1980).

    Article  ADS  CAS  Google Scholar 

  2. Share, G. H. et al. in Gamma Ray Transients and Related Astrophysical Phenomena (eds Lingenfelter, R. E., Hudson, H. S. & Worrall, D. M.) 45–53 (American Institute of Physics, New York, 1982).

    Google Scholar 

  3. Solar Geophysical Data—Prompt and Comprehensive Reps Nos 426–469 (NOAA, Boulder, 1980–83).

  4. Solar Geophysical Data—Prompt and Comprehensive Reps No. 470, Pt 1, 13 (NOAA, Boulder, 1983).

  5. Lin, R. P. & Ramaty, R. in Gamma Ray Spectroscopy in Astrophysics, 76–96 (NASA TM 79619, 1978).

    Google Scholar 

  6. Rice, J. R. IMSL Reference Manual (McGraw-Hill, New York, 1983).

    Google Scholar 

  7. Gerardi, G., Buccheri, R. & Sacco, B. COMPSTAT 82, 111–112 (Toulouse, 1982).

  8. Dennis, B. R. et al. Preprint TM 84998 (NASA, 1983).

  9. Dodson, H. W. & Hedeman, E. R. in Solar Terrestrial Physics Pt 1 (ed. Dyer, E. R.) 151–172 (Reidel, Dordrecht, 1970).

    Google Scholar 

  10. Vitinskii, Yu. I. Byull. soln. Dann 8,9 (1960); Solar Activity Forecasting (USSR Acad. Sci., Leningrad, 1962).

    Google Scholar 

  11. Wolff, C. L. Astrophys. J. 264, 667–676 (1983).

    Article  ADS  Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and Permissions

About this article

Cite this article

Rieger, E., Share, G., Forrest, D. et al. A 154-day periodicity in the occurrence of hard solar flares?. Nature 312, 623–625 (1984).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing