University of Oulu

Eleanna Asvestari, Ilya G. Usoskin, Gennady A. Kovaltsov, Mathew J. Owens, Natalie A. Krivova, Sara Rubinetti, Carla Taricco; Assessment of different sunspot number series using the cosmogenic isotope 44Ti in meteorites. Mon Not R Astron Soc 2017; 467 (2): 1608-1613. doi: 10.1093/mnras/stx190

Assessment of different sunspot number series using the cosmogenic isotope ⁴⁴Ti in meteorites

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Author: Asvestari, Eleanna1; Usoskin, Ilya G.1,2; Kovaltsov, Gennady A.3;
Organizations: 1Space Climate Research Unit, University of Oulu, FIN-90017 Oulu, Finland
2Sodankyl ̈ a Geophysical Observatory (Oulu unit), University of Oulu, FIN-90017 Oulu, Finland
3Ioffe Physical-Technical Institute, St. Petersburg, RU-194021, Russia
4Department of Meteorology, University of Reading, Earley Gate, Reading RG6 6BB, UK
5Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen, Germany
6Dipartimento di Fisica, Via P.Giuria 1, Universit ` a di Torino, I-10125 Torino, Italy
7Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese, Italy
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.5 MB)
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Language: English
Published: Oxford University Press, 2017
Publish Date: 2017-03-07


Many sunspot number series exist suggesting different levels of solar activity during the past centuries. Their reliability can be assessed only by comparing them with alternative indirect proxies. We test different sunspot number series against the updated record of cosmogenic radionuclide ⁴⁴Ti measured in meteorites. Two bounding scenarios of solar activity changes have been considered: the HH-scenario (based on the series by Svalgaard and Schatten), in particular, predicting moderate activity during the Maunder minimum, and the LL-scenario (based on the RG series by Lockwood et al.) predicting moderate activity for the 18th–19th centuries and the very low activity level for the Maunder minimum. For each scenario, the magnetic open solar flux, the heliospheric modulation potential and the expected production of ⁴⁴Ti were computed. The calculated production rates were compared with the corresponding measurements of ⁴⁴Ti activity in stony meteorites fallen since 1766. The analysis reveals that the LL-scenario is fully consistent with the measured ⁴⁴Ti data, in particular, recovering the observed secular trend between the 17th century and the Modern grand maximum. On the contrary, the HH-scenario appears significantly inconsistent with the data, mostly due to the moderate level of activity during the Maunder minimum. It is concluded that the HHscenario sunspot number reconstruction significantly overestimates solar activity prior to the mid-18th century, especially during the Maunder minimum. The exact level of solar activity after 1750 cannot be distinguished with this method, since both H- and L- scenarios appear statistically consistent with the data.

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Series: Monthly notices of the Royal Astronomical Society
ISSN: 0035-8711
ISSN-E: 1365-8711
ISSN-L: 0035-8711
Volume: 467
Issue: 2
Pages: 1608 - 1613
DOI: 10.1093/mnras/stx190
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: Contributions of E. Asvestari, I.G. Usoskin and G.A. Kovaltsov were done in the framework of the ReSoLVE Centre of Excellence (Academy of Finland, project no. 272157). M. Owens is funded by the UK Science and Technology Facilities Council (STFC) consolidated grant number ST/M000885/1. Part of thisworkwas supported by the COST Action ES1005 ‘Toward a more complete assessment of the impact of solar variability on the Earth’s climate’.
Academy of Finland Grant Number: 272157
Detailed Information: 272157 (Academy of Finland Funding decision)
Copyright information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.