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A Study of Variation of the 11-yr Solar Cycle before the onset of the Spoerer Minimum based on Annually measured 14C Content in tree Rings
Published online by Cambridge University Press: 22 November 2019
Abstract
Proxy-based observations of solar activity in the past have revealed long-term variations, such as the Gleissberg cycle (~88 yr), de Vries cycle (~200 yr), and the Hallstatt cycle (~2000 yr). Such long-term variations of solar activity sometimes cause the disappearance of sunspots for several decades. Currently, solar activity is becoming weaker, and there is a possibility that another long-term sunspot minimum could occur. However, the detailed mechanism of the weakening in solar activity is unknown, and the prediction of solar activity is ambiguous. In this study, we investigate the transitions of solar cycle length before the onset of the Spoerer Minimum, the longest grand minimum in the past 2000 yr. We measured the 14C content in an asunaro tree (Thujopsis dolabrata) excavated at Shimokita Peninsula from 1368–1420 CE using the compact AMS system at Yamagata University. It is found that the solar cycle lengthened to be 14–16 yr from 2 cycles before the onset of the Spoerer Minimum.
- Type
- Conference Paper
- Information
- Radiocarbon , Volume 61 , Issue 6: Radiocarbon 2018 Conference Proceedings Trondheim, Norway, June 17–22, 2018 Part 2 of 2 , December 2019 , pp. 1749 - 1754
- Copyright
- © 2019 by the Arizona Board of Regents on behalf of the University of Arizona
Footnotes
Selected Papers from the 23rd International Radiocarbon Conference, Trondheim, Norway, 17–22 June, 2018
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