Re-calibration of the Sunspot Number: Status Report
Abstract
We report progress on the ongoing recalibration of the Wolf sunspot number (SN) and Group sunspot number (GN) following the release of version 2.0 of SN in 2015. This report constitutes both an update of the efforts reported in the 2016 Topical Issue of Solar Physics and a summary of work by the International Space Science Institute (ISSI) International Team formed in 2017 to develop optimal SN and GN re-construction methods while continuing to expand the historical sunspot number database. Significant progress has been made on the database side while more work is needed to bring the various proposed SN and (primarily) GN reconstruction methods closer to maturity, after which the new reconstructions (or combinations thereof) can be compared with (a) ``benchmark'' expectations for any normalization scheme (e.g., a general increase in observer normalization factors going back in time), and (b) independent proxy data series such as F10.7 and the daily range of variations of Earth's undisturbed magnetic field. New versions of the underlying databases for SN and GN will shortly become available for years through 2022 and we anticipate the release of next versions of these two time series in 2024.
Keywords
Cite
@article{arxiv.2301.02084,
title = {Re-calibration of the Sunspot Number: Status Report},
author = {F. Clette and L. Lefèvre and T. Chatzistergos and H. Hayakawa and V. M. Carrasco and R. Arlt and E. W. Cliver and T. Dudok de Wit and T. Friedli and N. Karachik and G. Kopp and M. Lockwood and S. Mathieu and A. Muñoz-Jaramillo and M. Owens and D. Pesnell and A. Pevtsov and L. Svalgaard and I. G. Usoskin and L. van Driel-Gesztelyi and J. M. Vaquero},
journal= {arXiv preprint arXiv:2301.02084},
year = {2023}
}
Comments
21 figures, 4 tables. To be published in Solar Physics