Lefèvre, Laure ; Kalugodu, Chandrashekhar ; Mampaey, Benjamin

Poster presented at ESWW25, Umea on 2025-10-27

Abstract: Efforts have been undertaken by the solar community since 2010 to revise both the Sunspot Number and the Group Number series (SN and GN). I will present our latest achievements and our plans for the near future. First, since the last revision of SN in 2015, significant progress has been made in recovering and digitizing historical datasets, notably including the Mittheilungen from the Zürich Observatory. These recovered records enabled a new reconstruction of the SN series from 1814 to 1944 (Bhattacharya et al., 2022, 2023, 2024), and also led to several revised Group Number reconstructions (e.g. Svalgaard & Schatten 2016, Chatzistergos et al. 2017, Usoskin et al. 2021). Furthermore, in 2022, the WDC-SILSO team launched the FARSUN project, aiming to collect, harmonize, and centralize all available sunspot datasets into a single FAIR-compliant (Findable, Accessible, Interoperable, and Reusable) database hosted in Belgium. Second, if we look at the modern production of the SN and GN, in 2023, the WDC-SILSO launched a project to modernize the day-to-day computation of the SN, and add the production, at the same frequency, of the GN (Belgian SUNRISE). In summary, in the near future, by mid-2027, a historical database centralizing all available sunspot data will be put into action, and will keep being updated as new data is digitized. By the same time, the production of the SN will be modernized and GN will be produced by the WDC-SILSO with the same frequency as SN. At this time, new major versions of SN and GN will be released with complete transparency as to their construction.

Funding: FARSUN - SUNRISE/FARSUN - SUNRISE/FARSUN - SUNRISE