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

Toru Moriya, Hiroko Miyahara, Motonari Ohyama, Masataka Hakozaki, Mirei Takeyama, Hirohisa Sakurai, Fuyuki Tokanai

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

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.

Original languageEnglish
Pages (from-to)1749-1754
Number of pages6
JournalRadiocarbon
DOIs
Publication statusAccepted/In press - 2019 Jan 1

Keywords

  • 11-yr solar cycle
  • Spoerer Minimum
  • YU-AMS

ASJC Scopus subject areas

  • Archaeology
  • Earth and Planetary Sciences(all)

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