Abstract
The sunspot number is analyzed by using detailed sunspot data, including aspects of observability, sunspot sizes, and proper identification of sunspot groups as discrete entities of solar activity. The tests show that in addition to the subjective factors there are also objective causes of the ambiguities in the series of sunspot numbers. To introduce an alternative solar-activity measure, the physical meaning of the sunspot number has to be reconsidered. It contains two components whose numbers are governed by different physical mechanisms and this is one source of the ambiguity. This article suggests an activity index, which is the amount of emerged magnetic flux. The only long-term proxy measure is the detailed sunspot-area dataset with proper calibration to the magnetic flux. The Debrecen sunspot databases provide an appropriate source for the establishment of the suggested activity index.
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Acknowledgements
This work has been presented at the Sunspot Number Workshop held in Tucson, Arizona, January 2013; thanks are due to Edward W. Cliver for inviting Judit Muraközy and András Ludmány. The research leading to these results has received funding from the European Commission’s Seventh Framework Programme (FP7/2007-2013) under the grant agreement eHeroes (project n° 284461, www.eheroes.eu ).
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Sunspot Number Recalibration
Guest Editors: F. Clette, E.W. Cliver, L. Lefèvre, J.M. Vaquero, and L. Svalgaard
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Muraközy, J., Baranyi, T. & Ludmány, A. An Alternative Measure of Solar Activity from Detailed Sunspot Datasets. Sol Phys 291, 2941–2950 (2016). https://doi.org/10.1007/s11207-016-0898-x
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DOI: https://doi.org/10.1007/s11207-016-0898-x