Reconstruction of the Sunspot Group Number: The Backbone Method

2015/06/02 by Leif Svalgaard, Kenneth H. Schatten, Kennuth H. Schatten · 229 citations
Mathematics · Physics and Astronomy · #Astro and Planetary Science #Astronomy #Astrophysics #Character (mathematics) #Earth's magnetic field #Geodesy #Geography #Geometry #Group (periodic table) #History and Developments in Astronomy #Magnetic field #Mathematics #Meteorology #Nuclear physics #Physics #Plasma #Rigidity (electromagnetism) #Solar and Space Plasma Dynamics #Solar cycle #Solar wind #Sunspot #Sunspot number #astro-ph.SR

paper · pdf · doi:10.1007/s11207-015-0815-8

published in Solar Physics 291(9-10), 2653-2684 (Springer Science+Business Media) · Contribution to Topical Issue of Solar Physics on "Recalibration of the Sunspot Number", 34 pages, 36 Figures

arxiv created 2015/06/02 · openalex publication_date 2016/02/18 · arxiv updated 2016/03/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

We have reconstructed the sunspot group count, not by comparisons with other reconstructions and correcting those where they were deemed to be deficient, but by a re-assessment of original sources. The resulting series is a pure solar index and does not rely on input from other proxies, e.g. radionuclides, auroral sightings, or geomagnetic records. 'Backboning' the data sets, our chosen method, provides substance and rigidity by using long-time observers as a stiffness character. Solar activity, as defined by the Group Number, appears to reach and sustain for extended intervals of time the same level in each of the last three centuries since 1700 and the past several decades do not seem to have been exceptionally active, contrary to what is often claimed.

Citations

• Group Sunspot Numbers: A New Solar Activity Reconstruction

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