Recalibration of the Sunspot-Number: Status Report

2023/03/01 by F. Clette, Laure Lefèvre, L. Lefèvre +31 · 1 voice · 8 citations
Earth and Planetary Sciences · Physics and Astronomy · #Geophysics and Gravity Measurements #Ionosphere and magnetosphere dynamics #Solar and Space Plasma Dynamics

paper · pdf · doi:10.1007/s11207-023-02136-3

openalex publication_date 2023/03/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

Abstract We report progress on the ongoing recalibration of the Wolf sunspot number ( S_N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>S</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math> ) and group-sunspot number ( G_N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>G</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math> ) following the release of version 2.0 of S_N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>S</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math> 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 S_N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>S</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math> and G_N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>G</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math> reconstruction 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 S_N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>S</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math> and (primarily) G_N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>G</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math> 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 S_N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>S</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math> and G_N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>G</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math> will shortly become available for years through 2022 and we anticipate the release of the next versions of these two time series in 2024.

Citations

• Group Sunspot Numbers: A New Solar Activity Reconstruction
• Reconstruction of the Sunspot Group Number: The Backbone Method
• The Solar Dynamics Observatory (SDO)
• The Helioseismic and Magnetic Imager (HMI) Investigation for the Solar Dynamics Observatory (SDO)
• Sonnen — Beobachtungen im Jahre 1843
• The New Sunspot Number: Assembling All Corrections
• Group Sunspot Numbers: A New Solar Activity Reconstruction
• Revisiting the Sunspot Number
• Long-term changes in solar activity and irradiance

Cited by

• Assessment of sunspot number cross-calibration approaches
• Long-term changes in solar activity and irradiance
• Reconstruction of annual solar irradiance over the last three millennia
• Sunspot Observations in 1684-1702: John Flamsteed and Philippe de La Hire
• A Discussion of Implausible Total Solar-Irradiance Variations Since 1700
• Understanding the secular variability of solar irradiance: the potential of Ca II K observations
• Low-Latitude Sunspot Group Tilt Angles in 15-24 Activity Cycles
• Analyses of the Ancient Chinese Report on the Total Solar Eclipse in 709 BCE: Implications for the Contemporaneous Earth’s Rotation Speed and Solar Cycles

Discussions

• review https://doi.org/10.1007/s11207-023-02136-3 [bsky, 1 points, 1 comments]

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