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Major change of data set on July 1st, 2015

Over the past 4 years a community effort has been carried out to revise entirely the historical sunspot number series. A good overview of the analyses and identified corrections is provided in the recent review paper: 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. This is actually the first deep revision of the sunspot number since its creation By R. Wolf in 1849.

2014 : maximum year for solar cycle 24

Now that we completed the definitive sunspot numbers for 2014, we can conclude that the maximum of solar cycle 24 was reached in April 2014, with a maximum of the 13-month smoothed sunspot number at 81.8. Since then, solar activity has steadily declined (monthly mean sunspot number now around 40), but remained above 70 over many months, probably indicating that the annual mean for 2014 will also mark a yearly maximum at 78.9.

The SILSO upgrade continues: new prediction files and plots

Over past weeks, various upgrades took place in the backstage. We further improved the primary scripts for the sunspot number calculation. We also improved the internal data flow. The biggest transition was also the full migration from our old server, which served for the past 10 years, to the new one after a full year of cross-validation (double calculation in parallel). Although those deep changes are largely invisible to the outside world, they now put a fully new engine into our sunspot number production!

News 002: From SIDC to SILSO, why a new name?

Over the past month, we already got very positive feedback about our new Web site. Like for all new Web sites, we had to fix a few initial defects but now, the web site seems to be on its tracks. Sorry for any inconvenience!
On the other hand, giving a new name to our World Data Center (WDC) seems to have caused some confusion. Will SIDC disappear? What will it change in the SIDC and sunspot services? So, let us clarify this point.