Space Science Reviews

, Volume 186, Issue 1–4, pp 105–135 | Cite as

Solar Cycle Indices from the Photosphere to the Corona: Measurements and Underlying Physics

  • Ilaria ErmolliEmail author
  • Kiyoto Shibasaki
  • Andrey Tlatov
  • Lidia van Driel-Gesztelyi


A variety of indices have been proposed in order to represent the many different observables modulated by the solar cycle. Most of these indices are highly correlated with each other owing to their intrinsic link with the solar magnetism and the dominant eleven year cycle, but their variations may differ in fine details, as well as on short- and long-term trends. In this paper we present an overview of the indices that are often employed to describe the many features of the solar cycle, moving from the ones referring to direct observations of the inner solar atmosphere, the photosphere and chromosphere, to those deriving from measurements of the transition region and solar corona. For each index, we summarize existing measurements and typical use, and for those that quantify physical observables, we describe the underlying physics.


Solar cycle Solar atmosphere Solar magnetism 



The authors are grateful to the International Space Science Institute, Bern, for the organization of the workshop “The Solar Activity Cycle: Physical Causes and Consequences”, the invitation to contribute to it, and the kind support received to the purpose. The authors thank Fabrizio Giorgi for preparing Figs. 1 to 8. This study received funding from the European Union’s Seventh Programme for Research, Technological Development and Demonstration, under the Grant Agreements of the eHEROES (No. 284461,, SOLARNET (No. 312495,, and SOLID (No. 313188, projects. It was also supported by COST Action ES1005 “TOSCA” ( LvDG’s work was supported by the Hungarian Research grants OTKA K-081421 and K-109276, and by the STFC Consolidated Grant ST/H00260/1.

Final acknowledgements go to the many observers and astronomers, both amateur and professional, for performing the regular observations of the solar atmosphere and creating the databases of solar indices described in this paper.


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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  • Ilaria Ermolli
    • 1
    Email author
  • Kiyoto Shibasaki
    • 2
  • Andrey Tlatov
    • 3
  • Lidia van Driel-Gesztelyi
    • 4
    • 5
    • 6
  1. 1.INAF Osservatorio Astronomico di RomaMonte Porzio CatoneItaly
  2. 2.Nobeyama Solar Radio Observatory NAOJNaganoJapan
  3. 3.Kislovodsk Mountain Astronomical Station of the Pulkovo ObservatoryKislovodskRussia
  4. 4.Mullard Space Science LaboratoryUniversity College LondonSurreyUK
  5. 5.LESIA, Observatoire de Paris, CNRS, UPMCUniversité Paris DiderotParisFrance
  6. 6.Konkoly Observatory of the Hungarian Academy of SciencesBudapestHungary

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