Assessment of the Failure of Active Days Fraction Method of Sunspot\n Group Number Reconstructions

2017/06/04 by Leif Svalgaard, Kenneth H. Schatten, Svalgaard, Leif +1
Computer Science · Earth and Planetary Sciences · Physics and Astronomy · #FOS: Physical sciences #Geophysics and Gravity Measurements #Solar Radiation and Photovoltaics #Solar and Space Plasma Dynamics #Solar and Stellar Astrophysics (astro-ph.SR)

paper · pdf · doi:10.48550/arxiv.1706.01154

openalex publication_date 2017/06/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We identify several pairs of 'equivalent' observers defined as observers with\nequal or nearly equal 'observational threshold' areas of sunspots on the solar\ndisk as determined by the 'Active Days Fraction' method [e.g. Willamo et al.,\n2017]. For such pairs of observers, the ADF-method would be expected to map the\nactually observed sunspot group numbers for the individual observers to two\nreconstructed series that are very nearly equal and (it is claimed) represent\n'real' solar activity without arbitrary choices and deleterious,\nerror-accumulating 'daisy-chaining'. We show that this goal has not been\nachieved (for the critical period at the end of the 19th century and the\nbeginning of the 20th), rendering the ADF-methodology suspect and not reliable\nnor useful for studying the long-term variation of solar activity.\n

Citations

• Group Sunspot Numbers: A New Solar Activity Reconstruction
• On the Sunspot Group Number Reconstruction: The Backbone Method Revisited

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