Uncertainties in the Sunspot Numbers: Estimation and Implications
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Sunspot number series are subject to various uncertainties that are still poorly known. The need to understand these better was recently highlighted by the major revision of the international Sunspot Number (Clette et al., in Space Sci. Rev. 186, 35, 2014). We present the first thorough estimation of these uncertainties, which behave as Poisson-like random variables with a multiplicative coefficient that is time- and observatory-dependent. We provide a simple expression for these uncertainties, and reveal how their evolution in time coincides with changes in the observations and processing of the data. Knowing their value is essential for properly building composites out of multiple observations, and for preserving the stability of the composites in time.
We gratefully acknowledge funding from the European Community’s Seventh Framework Programme (FP7, 2012) under grant agreement no 313188 (SOLID, projects.pmodwrc.ch/solid ). We sincerely thank the anonymous referee for carefully reviewing the manuscript, and for making pertinent comments.
Disclosure of Potential Conflicts of Interest
The authors declare that they have no conflicts of interest.
- Bray, R.J., Loughhead, R.E.: 1964, Sunspots, Chapman & Hall, London. Google Scholar
- Clette, F., Lefèvre, L., Cagnotti, M., Cortesi, S., Bulling, A.: 2016, The revised Brussels–Locarno Sunspot Number (1981 – 2015). Solar Phys. DOI
- Cliver, E.W.: 2016, The Discontinuity in 1885 in the Group Sunspot Number. Solar Phys. DOI
- Dudok de Wit, T., Kopp, G., Fröhlich, C., Schöll, M.: 2016, Methodology to create a new total solar irradiance record: making a composite out of multiple data records. Geophys. Res. Lett., submitted. Google Scholar
- Friedli, T.K.: 2016, The construction of the Wolf series from 1749 to 1980. Solar Phys., submitted. Google Scholar
- Lockwood, M., Owens, M.J., Barnard, L.A., Usoskin, I.G.: 2016a, An assessment of sunspot number data composites over 1845 – 2014. Astrophys. J., accepted. Google Scholar
- Lockwood, M., Owens, M.J., Barnard, L., Usoskin, I.G.: 2016b, Tests of sunspot number sequences: 3. Effects of regression procedures on the calibration of historic sunspot data. Solar Phys. DOI.
- Morfill, G.E., Scheingraber, H., Voges, W., Sonett, C.P.: 1991, Sunspot number variations – stochastic or chaotic. In: Sonett, C.P., Giampapa, M.S., Matthews, M.S. (eds.) The Sun in Time, 30, Springer, New York. Google Scholar
- Svalgaard, L., Schatten, K.H.: 2016, Reconstruction of the Sunspot Group Number: the Backbone method. Solar Phys. DOI
- Taylor, B.N., Kuyatt, C.E.: 1994, Guidelines for evaluating and expressing the uncertainty of NIST measurement results. Technical report 1297, National Institute of Standards and Technology, Washington, DC. Google Scholar
- Vaquero, J.M., Vázquez, M.: 2009, The Sun Recorded Through History: Scientific Data Extracted from Historical Documents, Astrophysics and Space Science Library 361, Springer, Heidelberg. Google Scholar