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  1. Article

    Open Access

    Prolonged production of 14C during the ~660 BCE solar proton event from Japanese tree rings

    Annual rings record the intensity of cosmic rays (CRs) that had entered into the Earth’s atmosphere. Several rapid 14C increases in the past, such as the 775 CE and 994CE 14C spikes, have been reported to origina...

    Hirohisa Sakurai, Fuyuki Tokanai, Fusa Miyake, Kazuho Horiuchi… in Scientific Reports (2020)

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  2. Article

    Open Access

    Regional climate pattern during two millennia estimated from annual tree rings of Yaku cedar trees: a hint for solar variability?

    We analyzed trees that have survived on Yaku island (Yakushima) for 2,000 years. Quite surprisingly, the Fourier and wavelet analyses of the annual growth rate identified 2 cycles of periodicities of 11 and (2...

    Yasushi Muraki, Takumi Mitsutani, Shoichi Shibata… in Earth, Planets and Space (2015)

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  3. Article

    Correction: Corrigendum: Another rapid event in the carbon-14 content of tree rings

    Nature Communications 4: Article number: 1748 (2013); Published: 23 April 2013; Updated: 7 November 2013. The original version of this Article contained a chronological error concerning the counting of tree ri...

    Fusa Miyake, Kimiaki Masuda, Toshio Nakamura in Nature Communications (2013)

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  4. No Access

    Article

    Another rapid event in the carbon-14 content of tree rings

    Previously, we have observed that the atmospheric 14C content measured in tree rings showed a strong increase from AD 774 to 775. Although the cause of this event can be explained by a large solar proton event or...

    Fusa Miyake, Kimiaki Masuda, Toshio Nakamura in Nature Communications (2013)

  5. No Access

    Article

    A signature of cosmic-ray increase in ad 774–775 from tree rings in Japan

    A rapid increase in the 14C content of Japanese cedar tree rings occurred during ad 774 to 775, and is about 20 times larger than the change attributed to ordinary solar modulation; neither a solar flare nor a lo...

    Fusa Miyake, Kentaro Nagaya, Kimiaki Masuda, Toshio Nakamura in Nature (2012)

  6. No Access

    Article

    Cyclicity of Solar Activity During the Maunder Minimum Deduced from Radiocarbon Content

    This paper presents the features of the “eleven-year” cycle of radiocarbon content during the period of prolonged sunspot minimum called the Maunder Minimum (1645–1715 AD). Whether or not the Sun had maintained t...

    Hiroko Miyahara, Kimiaki Masuda, Yasushi Muraki, Hideki Furuzawa… in Solar Physics (2004)

  7. No Access

    Article

    Wide-Field Camera for Gravitational Microlensing Survey: MOA-cam2

    We have constructed a large, mosaic CCD camera called MOA-cam2 which has 4096 × 6144-pixelsto search for gravitational microlensing events. MOA-cam2 has three4096 × 2048-pixel SITe CCD chips, which have a very...

    Toshifumi Yanagisawa, Yasushi Muraki, Yutaka Matsubara, Fumio Abe… in Experimental Astronomy (2000)