Working Meeting - Implications and prospects for the new Sunspot Number

Frédéric Clette, Laure Lefèvre
Tuesday, 24th 17:00 - 18:30, Mercator

After a 4-year joint effort, a new deeply revised version of the sunspot number and group number series has been released in August 2015 and is now available on the Web site of the World data Center SILSO. As this revision brings large changes (up to 40%) and strongly modifies secular trends in solar activity adopted in past works, we invite researchers to try out the new corrected series in their own models and data analyses and to join this working session to report their first conclusions and submit their comments and questions.

The update of the sunspot series was also associated with important changes in past conventions (new scales) and with the necessary implementation of a structured scheme for managing future updates to this reference series and the development of standardized digital catalogues of historical observations. Therefore, we would like also to initiate an open discussion on current and future data standards and products for the sunspot number.

Sample topics can be:
- Which documentation and metadata should be archived with each version of the sunspot number?
- Should we continue producing the group number next to the sunspot number, now they are reconciled?
- Would a group number-sunspot number composite series be useful and meaningful or should they be kept fully separated?
- Which estimate of the accuracy can be adopted for epochs when sunspot observations are very scarce?
- Is it worth publishing mean sunspot numbers per Carrington rotation next to the classical monthly means?
- How to properly include null values in global averages and correlations?
- How can we implement the digitization of historical observations and the standardization of sunspot digital catalogues?
- What are the prospects for reconstructing hemispheric sunspot or group numbers over past centuries?
- Which long-term product or proxy derived from the sunspot number could help in your research?

Other ideas or questions? Please join us. We are looking forward to your input.