Abstract
In 1876, Alfred Wolfer started observing the Sun and recording the properties of sunspots alongside Rudolf Wolf. Their observations became the basis for the construction of the sunspot-number series. After Wolf’s death in 1893, Wolfer became the primary observer for the sunspot-number series. Even though the observations of Wolf and Wolfer had an overlap of almost 17 years (1876–1893), this shift of primary observer from Wolf to Wolfer seems to have led to inconsistencies in the sunspot-number series, primarily due to inhomogeneities in Wolf’s observations. To address this issue we digitise Mittheilungen (Wolf’s journals) and analyse their tabulated datasets. These journals include the raw sunspot data from various observers that the Zürich Observatory used to compile the sunspot number series (SNV1). These datasets have been used as source data for the construction of the first version of the sunspot number (SNV1) series, but they were not digitally accessible for a recalibration of the sunspot-number series until recently. We have also acquired external datasets from recent archival investigations for contemporaneous sunspot observations. In this study, we use the Mittheilungen dataset to produce a new recalibration of the sunspot-number series covering 1816–1944, using four major observers (Tevel, Schwabe, Weber and Wolfer) as backbones. The availability of the raw data allows us to identify issues in the determination of the scaling factors or \(k\)-factors, between the records of different observers, but also the use of modern techniques for cross-calibrations. Our reconstruction for the years 1816–1944 is carried out with a novel method inspired by Chatzistergos et al. (Astron. Astrophys. 602, A69, 2017) allowing us to eliminate inconsistencies that resulted from the application of erroneous \(k\)-factors.
Similar content being viewed by others
Data Availability
H. Hayakawa thanks the Misawa Memorial Archives and Nagano Prefectural Suwa Seiryo Senior High School for letting us access, research and publicise Misawa’s sunspot drawings, Tom Teague for his recounting efforts of Carrington’s book, P. Amand for letting him access the data in Kremsmünster Observatory, and Frédéric Clette for his valuable discussions for usage of historical sunspot records.
References
Aparicio, A.J., Vaquero, J.M., Carrasco, V., Gallego, M.: 2014, Sunspot numbers and areas from the Madrid Astronomical Observatory (1876–1986). Solar Phys. 289, 4335.
Arlt, R., Vaquero, J.M.: 2020a, Historical sunspot records. Living Rev. Solar Phys. 17, 1. DOI. ADS.
Arlt, R., Vaquero, J.M.: 2020b, Historical sunspot records. Living Rev. Solar Phys. 17, 1. DOI. ADS.
Arlt, R., Leussu, R., Giese, N., Mursula, K., Usoskin, I.G.: 2013, Sunspot positions and sizes for 1825-1867 from the observations by Samuel Heinrich Schwabe. Mon. Not. Roy. Astron. Soc. 433, 3165. DOI. ADS.
Bhattacharya, S., Teague, E.T.H., Fay, S., Lefèvre, L., Jansen, M., Clette, F.: 2021, A modern reconstruction of Richard Carrington’s observations (1853-1861). Solar Phys. 296, 118. DOI. ADS.
Bhattacharya, S., Lefèvre, L., Hayakawa, H., Jansen, M., Clette, F.: 2023, Scale transfer in 1849: Heinrich Schwabe to Rudolf Wolf. Solar Phys. 298, 12. DOI. ADS.
Carrasco, V.M.S.: 2021, Number of sunspot groups and individual sunspots recorded by tevel for the period 1816-1836 in the Dalton Minimum. Astrophys. J. 922, 58. DOI. ADS.
Carrasco, V.M.S., Vaquero, J.M., Gallego, M.C., Trigo, R.M.: 2013, Forty two years counting spots: solar observations by D.E. Hadden during 1890-1931 revisited. New Astron. 25, 95. DOI. ADS.
Carrasco, V.M., Vaquero, J.M., Aparicio, A.J., Gallego, M.: 2014, Sunspot catalogue of the Valencia Observatory (1920–1928). Solar Phys. 289, 4351.
Carrasco, V., Bertolin, C., Domínguez-Castro, F., de Ferri, L., Gallego, M., Vaquero, J.: 2020b, Sunspot records by Antonio Colla just after the Dalton Minimum. Solar Phys. 295, 112.
Carrasco, V.M.S., Gallego, M.C., Arlt, R., Vaquero, J.M.: 2020, Revisiting the amplitude of solar cycle 9: the case of sunspot observations by W.C. Bond. Solar Phys. 295, 127. DOI. ADS.
Carrasco, V., Gallego, M., Arlt, R., Vaquero, J.: 2020a, Revisiting the amplitude of solar cycle 9: the case of sunspot observations by WC Bond. Solar Phys. 295, 127.
Carrasco, V.M.S., Gallego, M.C., Villalba Álvarez, J., Vaquero, J.M., Hayakawa, H.: 2021a, Analyses of early sunspot records by Jean Tarde (1615–1617) and Jan Smogulecki (1621–1625). Solar Phys. 296, 170. DOI. ADS.
Carrasco, V.M.S., Munoz-Jaramillo, A., Nogales, J.M., Gallego, M.C., Vaquero, J.M.: 2021b, Sunspot catalog (1921-1935) and area series (1886-1940) from the Stonyhurst College Observatory. Astrophys. J. Suppl. 256, 38. DOI. ADS.
Carrasco, V.M.S., Muñoz-Jaramillo, A., Gallego, M.C., Vaquero, J.M.: 2022, Revisiting Christoph Scheiner’s sunspot records: a new perspective on solar activity of the early telescopic era. Astrophys. J. 927, 193. DOI. ADS.
Chatzistergos, T.: 2017, Analysis of historical solar observations and long-term changes in solar irradiance. PhD thesis, Uni-edition. 978-3-944072-55-5 DOI. ADS.
Chatzistergos, T., Krivova, N.A., Yeo, K.L.: 2023, Long-term changes in solar activity and irradiance. J. Atmos. Solar-Terr. Phys. 252, 106150. DOI. https://www.sciencedirect.com/science/article/pii/S1364682623001487.
Chatzistergos, T., Usoskin, I.G., Kovaltsov, G.A., Krivova, N.A., Solanki, S.K.: 2017, New reconstruction of the sunspot group numbers since 1739 using direct calibration and “backbone” methods. Astron. Astrophys. 602, A69. DOI. ADS.
Clette, F., Lefèvre, L.: 2016, The new sunspot number: assembling all corrections. Solar Phys. 291, 2629. DOI. ADS.
Clette, F., Berghmans, D., Vanlommel, P., Van der Linden, R.A.M., Koeckelenbergh, A., Wauters, L.: 2007, Adv. Space Res. 40, 919.
Clette, F., Svalgaard, L., Vaquero, J.M., Cliver, E.W.: 2014, Revisiting the sunspot number. A 400-year perspective on the solar cycle. Space Sci. Rev. 186, 35. DOI. ADS.
Clette, F., Cliver, E.W., Lefèvre, L., Svalgaard, L., Vaquero, J.M., Leibacher, J.W.: 2016, Preface to topical issue: recalibration of the sunspot number. Solar Phys. 291, 2479. DOI. ADS.
Clette, F., Lefèvre, L., Bechet, S., Ramelli, R., Cagnotti, M.: 2021, Reconstruction of the sunspot number source database and the 1947 Zurich discontinuity. Solar Phys. 296, 1.
Clette, F., Lefèvre, L., Chatzistergos, T., Hayakawa, H., Carrasco, V.M.S., Arlt, R., Cliver, E.W., Dudok de Wit, T., Friedli, T.K., Karachik, N., Kopp, G., Lockwood, M., Mathieu, S., Muñoz-Jaramillo, A., Owens, M., Pesnell, D., Pevtsov, A., Svalgaard, L., Usoskin, I.G., van Driel-Gesztelyi, L., Vaquero, J.M.: 2023, Recalibration of the sunspot-number: status report. Solar Phys. 298, 44. DOI. ADS.
Cliver, E.W., Ling, A.G.: 2016, The discontinuity circa 1885 in the group sunspot number. Solar Phys. 291, 2763. DOI. ADS.
Diercke, A., Arlt, R., Denker, C.: 2015, Digitization of sunspot drawings by Spörer made in 1861–1894. Astron. Nachr. 336, 53.
Dudok de Wit, T., Lefèvre, L., Clette, F.: 2016a, Uncertainties in the sunspot numbers: estimation and implications. Solar Phys. 291, 2709.
Dudok de Wit, T., Lefèvre, L., Clette, F.: 2016b, Uncertainties in the sunspot numbers: estimation and implications. Solar Phys. 291, 2709. DOI.
Ermolli, I., Chatzistergos, T., Giorgi, F., Carrasco, V.M.S., Aparicio, A.J.P., Chinnici, I.: 2023, Solar observations by Angelo Secchi. I. Digitization of original documents and analysis of group numbers over the period of 1853–1878. Astrophys. J. Suppl. Ser. 269, 53. DOI.
Friedli, T.K.: 2016, Sunspot observations of Rudolf Wolf from 1849–1893. Solar Phys. 291, 2505. DOI. ADS.
Friedli, T.K.: 2020, Recalculation of the Wolf series from 1877 to 1893. Solar Phys. 295, 72. DOI. ADS.
Fujiyama, M., Hayakawa, H., Iju, T., Kawai, T., Toriumi, S., Otsuji, K., Kondo, K., Watanabe, Y., Nozawa, S., Imada, S.: 2019, Revisiting Kunitomo’s sunspot drawings during 1835–1836 in Japan. Solar Phys. 294, 43.
Gray, L.J., Beer, J., Geller, M., Haigh, J.D., Lockwood, M., Matthes, K., Cubasch, U., Fleitmann, D., Harrison, G., Hood, L., Luterbacher, J., Meehl, G.A., Shindell, D., van Geel, B., White, W.: 2010, Solar influences on climate. Ann. Geophys. 48, 4001. DOI. ADS
Hayakawa, H., Ebihara, Y., Willis, D.M., Toriumi, S., Iju, T., Hattori, K., Wild, M.N., Oliveira, D.M., Ermolli, I., Ribeiro, J.R., Correia, A.P., Ribeiro, A.I., Knipp, D.J.: 2019, Temporal and spatial evolutions of a large sunspot group and great auroral storms around the Carrington event in 1859. Space Weather 17, 1553. DOI. ADS.
Hayakawa, H., Besser, B.P., Iju, T., Arlt, R., Uneme, S., Imada, S., Bourdin, P.-A., Kraml, A.: 2020, Thaddäus Derfflinger’s sunspot observations during 1802-1824: a primary reference to understand the Dalton Minimum. Astrophys. J. 890, 98. DOI. ADS.
Hayakawa, H., Iju, T., Kuroyanagi, C., Carrasco, V.M.S., Besser, B.P., Uneme, S., Imada, S.: 2021a, Johann Christoph Müller’s sunspot observations in 1719–1720: snapshots of the immediate aftermath of the Maunder Minimum. Solar Phys. 296, 154. DOI. ADS.
Hayakawa, H., Uneme, S., Besser, B.P., Iju, T., Imada, S.: 2021b, Stephan Prantner’s sunspot observations during the Dalton Minimum. Astrophys. J. 919, 1. DOI. ADS.
Hayakawa, H., Uneme, S., Besser, B.P., Iju, T., Imada, S.: 2021c, Stephan Prantner’s sunspot observations during the Dalton Minimum. Astrophys. J. 919, 1. DOI. ADS.
Hayakawa, H., Arlt, R., Iju, T., Besser, B.: 2023a, Karl von Lindener’s sunspot observations during 1800–1827: another long-term dataset for the Dalton Minimum. J. Space Weather Space Clim., in press. DOI.
Hayakawa, H., Suyama, T., Clette, F., Bhattacharya, S., Lefèvre, L., Ohnishi, K.: 2023b, Katsue Misawa’s sunspot observations in 1921–1934: a primary reference for the Wolfer-Brunner transition. Mon. Not. Roy. Astron. Soc., in press. DOI.
Hoyt, D.V., Schatten, K.H.: 1998a, Group sunspot numbers: a new solar activity reconstruction. Solar Phys. 179, 189. DOI. ADS.
Hoyt, D.V., Schatten, K.H.: 1998b, Group sunspot numbers: a new solar activity reconstruction. Solar Phys. 181, 491. DOI. ADS.
IPCC: 2021, Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge. DOI.
Izenman, A.J.: 1985, J.R. Wolf and the Zurich sunspot relative numbers. Math. Intell. 7, 79.
Kendall, M.G.: 1962, Rank correlation methods. Technical report.
Konno, H., Koshizuka, T.: 2005, Mean-absolute deviation model. IIE Trans. 37, 893.
Lefevre, L., Clette, F., Mathieu, S., Delouille, V., von Sachs, R.: 2018, The sunspot number recalibration. In: Catalyzing Solar Connections, 2. ADS.
Mathieu, S., von Sachs, R., Ritter, C., Delouille, V., Lefèvre, L.: 2019, Astrophys. J. 886, 7.
Owens, B.: 2013, Long-term research: slow science. Nature 495, 300. DOI. ADS.
Sivaraman, K.R., Gupta, S.S., Howard, R.F.: 1993, Measurement of Kodiakanal white-light images – part one. Solar Phys. 146, 27. DOI. ADS.
Solanki, S.K., Krivova, N.A., Haigh, J.D.: 2013, Solar irradiance variability and climate. Annu. Rev. Astron. Astrophys. 51, 311. DOI.
Spoerer, F., Maunder, E.: 1890, Prof. Spoerer’s researches on sun-spots. Mon. Not. Roy. Astron. Soc. 50, 251.
Svalgaard, L.: 2010, Updating the historical sunspot record. In: Cranmer, S.R., Hoeksema, J.T., Kohl, J.L. (eds.) SOHO-23: Understanding a Peculiar Solar Minimum, Astronomical Society of the Pacific Conference Series 428, 297. DOI. ADS.
Svalgaard, L., Schatten, K.H.: 2016, Reconstruction of the sunspot group number: the backbone method. Solar Phys. 291, 2653. DOI. ADS.
Usoskin, I.G., Kovaltsov, G.A., Chatzistergos, T.: 2016, Dependence of the sunspot-group size on the level of solar activity and its influence on the calibration of solar observers. Solar Phys. 291, 3793.
Usoskin, I., Kovaltsov, G., Kiviaho, W.: 2021, Robustness of solar-cycle empirical rules across different series including an updated Active-Day Fraction (ADF) sunspot group series. Solar Phys. 296, 13. DOI. ADS.
Usoskin, I.G., Kovaltsov, G.A., Lockwood, M., Mursula, K., Owens, M., Solanki, S.K.: 2016a, A new calibrated sunspot group series since 1749: statistics of active day fractions. Solar Phys. 291, 2685. DOI. ADS.
Usoskin, I.G., Kovaltsov, G.A., Lockwood, M., Mursula, K., Owens, M., Solanki, S.K.: 2016b, A new calibrated sunspot group series since 1749: statistics of active day fractions. Solar Phys. 291, 2685. DOI. ADS.
Vaquero, J.M., Vázquez, M.: 2009, The Sun Recorded Through History 361, Springer, Berlin.
Vaquero, J.M., Svalgaard, L., Carrasco, V.M.S., Clette, F., Lefèvre, L., Gallego, M.C., Arlt, R., Aparicio, A.J.P., Richard, J.-G., Howe, R.: 2016, A revised collection of sunspot group numbers. Solar Phys. 291, 3061. DOI. ADS.
Willamo, T., Usoskin, I.G., Kovaltsov, G.A.: 2017, Updated sunspot group number reconstruction for 1749-1996 using the active day fraction method. Astron. Astrophys. 601, A109. DOI. ADS.
Wolf, R.: 1848, Nachrichten Von der Sternwarte in Bern. DOI. ADS.
Wolf, R.: 1859, Mittheilungen über die Sonnenflecken IX. Astron. Mitt. Eidgenöss. Sternwarte Zür. 1, 207. ADS.
Wolf, R.: 1861, Mittheilungen über die Sonnenflecken XIII. Astron. Mitt. Eidgenöss. Sternwarte Zür. 2, 83. ADS.
Wolf, R.: 1862, Mittheilungen über die Sonnenflecken XIV. Astron. Mitt. Eidgenöss. Sternwarte Zür. 2, 119. ADS.
Wolf, R.: 1864, Mittheilungen über die Sonnenflecken XVI. Astron. Mitt. Eidgenöss. Sternwarte Zür. 2, 163. ADS.
Wolf, R.: 1878b, Beobachtungen der Sonnenflecken, ETH Bibliothek, Hochschularchiv, Hs 368:46, 1Bd. Unpublished manuscript, Zurich.
Wolf, R.: 1890, Astronomische Mittheilungen LXXVI. Astron. Mitt. Eidgenöss. Sternwarte Zür. 8, 217. ADS.
Wolf, R., Brunner, W.: 1929, Astronomische Mittheilungen Nr CXVIII. Astron. Mitt. Eidgenöss. Sternwarte Zür. 12, 283. ADS.
Wolf, R., Wolfer, A.: 1894, Astronomische Mittheilungen LXXXIV. Astron. Mitt. Eidgenöss. Sternwarte Zür. 9, 109. ADS.
Acknowledgments
The authors would like to thank Dr. Frédéric Clette for his constructive comments. The authors would also like to thank the reviewer and the Editor for his/her constructive comments. L. Lefèvre, T. Chatzistergos and H. Hayakawa wish to acknowledge the support of ISSI https://www.issibern.ch/teams/sunspotnoser/.
Funding
This work was supported by a PhD grant awarded by the Royal Observatory of Belgium to S. Bhattacharya. H. Hayakawa’s research was conducted under the financial support of JSPS Grant-in-Aids JP20K20918, JP20H05643, JP21K13957 and JP22K02956. H. Hayakawa has been partly funded by JSPS Overseas Challenge Program for Young Researchers, the ISEE director’s leadership fund for FYs 2021–2023, Young Leader Cultivation (YLC) program of Nagoya University, Tokai Pathways to Global Excellence (Nagoya University) of the Strategic Professional Development Program for Young Researchers (MEXT), the young researcher units for the advancement of new and undeveloped fields, the Institute for Advanced Research, Nagoya University of the Program for Promoting the Enhancement of Research Universities, and NIHU Multidisciplinary Collaborative Research Projects NINJAL unit “Rediscovery of Citizen Science Culture in the Regions and Today”.
Author information
Authors and Affiliations
Contributions
S.B , L.L and T.C wrote the main manuscript text and all authors reviewed the manuscript.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Bhattacharya, S., Lefèvre, L., Chatzistergos, T. et al. Rudolf Wolf to Alfred Wolfer: The Transfer of the Reference Observer in the International Sunspot Number Series (1876–1893). Sol Phys 299, 45 (2024). https://doi.org/10.1007/s11207-024-02261-7
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s11207-024-02261-7