This section contains past versions of the Sunspot Number data.
Each version is uniquely identified by a 2-digit version number N.M, with:
- N: the primary number that changes for each new version where the sunspot numbers were collectively modified by any kind of correction.
- M: a second sub-version number is used to indicate secondary modifications that do not change the numbers themselves (e.g. new error estimates) or that involve only isolated modifications of the values (e.g. a typo found in a single daily value).
All files belonging to one version include the version number in the filename.
Each version will be documented by a description of the incremental changes relative to the previous version and by associated files (scientific publications, links to relevant Web pages).
This is the initial Sunspot Number series that was built without any subsequent modification by the Zürich Observatory, from R. Wolf in 1849 to M. Waldmeier in 1980, and by the Royal Observatory of Belgium since 1981 (WDC - SIDC, now SILSO).
For the first upgrade of the sunspot number to version 2.0, we first make available here the original files without modification (original filenames and same internal format), to leave time for our users to get used to the new data scheme. However, for global coherency, in a few months, those files will be converted to the same file format as version 2.0. As no documentation was ever attached to those files by our predecessors and because the scarce information is dispersed over many publications, the documentation of version 1.0 will be built progressively.
A recent synthesis of the construction of the original sunspot can be found in:
Clette, F., Svalgaard, L., Vaquero, J.M., Cliver, E. W.,“Revisiting the Sunspot Number. A 400-Year Perspective on the Solar Cycle”, Space Science Reviews, Volume 186, Issue 1-4, pp. 35-103. (see initial section and the many references cited therein)
Different relevant presentations from F. Clette, T. Friedli, L. Svalgaard, R. Arlt and others can be found in the Wiki of the Sunspot Number Workshops:
A thematic issue of the Solar Physics Journal is in preparation by mid-2015 and will gather many papers relevant to the V1.0 to V2.0 transition.