Working Meeting - Coordinated upgrades of sunspot numbers

Frédéric Clette (ROB); Laure Lefèvre (ROB)
Tuesday 15th, 15:00-16:30, Mercator

Soon after the 2015 release of the new and improved International Sunspot Number by the WDC-SILSO, several alternate Group and Sunspot series have been published independently over just a few months. As each of those series is promoted as the best version of this standard solar activity record, this proliferation created some confusion among users, who now wonder which series should be trusted. Several new flaws have already been found in some of those recent sunspot number series, which were supposed to eliminate flaws in earlier versions. The quality and overall validity of those new series thus deserve deeper scrutiny and a better coordination of the various research teams is thus also needed.

This working meeting will aim at finding how to best progress in a coordinated manner for the validation of these present series and for the future upgrades of the sunspot number.
We will start with a survey of all the GN and SN series published since 2014, analyzing their weaknesses and strengths. Secondly, we will share all ideas regarding the necessary corrections and their order of priority. And lastly, we will discuss the possible organizational schemes now in development for investigating and approving in a coordinated manner each new correction to the sunspot and group number series. This scheme should involve all experts in the field and ensure an open exchange of data and processing software, but it can take various forms: topical working groups, regular Sunspot Workshops, IAU supervision, etc... We invite the community to join this important discussion for the future of this fully-revived long-term solar activity reference.