The Sun exhibits centennial-scale activity variations and sometimes encounters grand solar minimum when solar activity becomes extremely weak and sunspots disappear for several decades. Such an ...extreme weakening of solar activity could cause severe climate, causing massive reductions in crop yields in some regions. During the past decade, the Sun's activity has tended to decline, raising concerns that the Sun might be heading for the next grand minimum. However, we still have an underdeveloped understanding of solar dynamo mechanisms and hence precise prediction of near-future solar activity is not attained. Here we show that the 11-year solar cycles were significantly lengthened before the onset of the Maunder Minimum (1645-1715 CE) based on unprecedentedly high-precision data of carbon-14 content in tree rings. It implies that flow speed in the convection zone is an essential parameter to determine long-term solar activity variations. We find that a 16 year-long cycle had occurred three solar cycles before the onset of prolonged sunspot disappearance, suggesting a longer-than-expected preparatory period for the grand minimum. As the Sun has shown a tendency of cycle lengthening since Solar Cycle 23 (1996-2008 CE), the behavior of Solar Cycle 25 can be critically important to the later solar activity.
Abstract
Annual rings record the intensity of cosmic rays (CRs) that had entered into the Earth’s atmosphere. Several rapid
14
C increases in the past, such as the 775 CE and 994CE
14
C spikes, have ...been reported to originate from extreme solar proton events (SPEs). Another rapid
14
C increase, also known as the ca. 660 BCE event in German oak tree rings as well as increases of
10
Be and
36
Cl in ice cores, was presumed similar to the 775 CE event; however, as the
14
C increase of approximately 10‰ in 660 BCE had taken a rather longer rise time of 3–4 years as compared to that of the 775 CE event, the occurrence could not be simply associated to an extreme SPE. In this study, to elucidate the rapid increase in
14
C concentrations in tree rings around 660 BCE, we have precisely measured the
14
C concentrations of earlywoods and latewoods inside the annual rings of Japanese cedar for the period 669–633 BCE. Based on the feature of
14
C production rate calculated from the fine measured profile of the
14
C concentrations, we found that the
14
C rapid increase occurred within 665–663.5 BCE, and that duration of
14
C production describing the event is distributed from one month to 41 months. The possibility of occurrence of consecutive SPEs over up to three years is offered.
We present two new millennium-long tree-ring oxygen isotope chronologies for central and northern Japan, based on 9693 annually resolved measurements of tree-ring oxygen isotopes from 39 unearthed ...samples consisting mainly of Japanese cedar (Cryptomeria japonica). These chronologies were developed through cross-dating of tree-ring widths and δ18O data from multiple samples covering the periods 2349–1009 BCE (1341 yr) and 1412–466 BCE (947 yr) for central and northern Japan, respectively. In combination with our published chronology for central Japan, the tree-ring δ18O dataset currently available covers the past 4354 yr (2349 BCE to 2005 CE), which represents the longest annually resolved tree-ring δ18O dataset for Asia. Furthermore, the high-resolution temporal record of 14C contents independently developed by Sakurai et al. (2020) was reproduced by our 14C measurements of earlywood and latewood in annual rings for the period 667–660 BCE.
A time-of-flight (TOF) detector with a large entrance foil (effective area of 154 cm2) was developed as part of the detection system to search for new elements of Z = 119 and beyond at RIKEN. We ...obtained a detection efficiency of approximately 100% for charged particles passing through the center region of the entrance foil. On the other hand, the detection efficiency decreased to approximately 23% in the edge region of the entrance foil. In this study, the modification of the internal electric field of the TOF detector is considered and realized to improve the detection efficiency. The validity of the modification is investigated by simulation. Furthermore, the detection efficiency is investigated through offline and beam experiments while modifying the internal electric field. The obtained results establish that the detection efficiency is improved by modifying the internal electric field.
Carbon‐14 in tree rings have suggested there had been multiple extreme solar proton events (SPEs) in the past. While the largest events such as in 774–775 CE can be significantly detected by the ...typical precision of accelerator mass spectrometry, smaller but possibly more frequent events have been difficult to be detected. Thus, the frequency or any characteristics of such relatively smaller events are still largely unknown. In this paper, we report that large SPEs had occurred in 1261–1262, 1268–1269, and 1279–1280 CE before the onset of the Wolf minimum based on high‐precision carbon‐14 analyses. It is suggested that they had occurred at the maximum and the declining phase of solar cycles, and that they had occurred during the transition time of solar activity into a deep minimum. We propose that this episode may provide a unique opportunity to elucidate a potential interaction between the solar dynamo and extreme solar flares.
Plain Language Summary
The Sun is a magnetically active star and occasionally cause intense bursts that sometimes accompany the ejection of energetic protons, described as the solar proton events. In this paper, we report that there were three intense solar proton events in the thirteenth century, just before the onset of the Wolf grand minimum. We propose that these events may be related to the weakening of solar activity during that time.
Key Points
Multiple abrupt increases in carbon‐14 content were found during the transition time of solar activity into the grand minimum state
They occurred at solar activity maximum or at the declining phase of solar cycles, suggesting that they originate from solar proton events
The Wolf minimum may provide a unique opportunity to potentially deepen the understanding of the solar dynamo
In 2009, Yamagata University installed a compact 14C accelerator mass spectrometry (YU-AMS) system and an automated graphitization line. The YU-AMS system is based on a 0.5 MV pelletron accelerator ...(1.5SDH-1) developed by National Electrostatics Corporation (NEC). A second automated graphitization line and an additional ion source of the YU-AMS system were installed in 2014. Approximately 2,000 samples have been measured per year using the system since 2010. The long-term stability of the system from 2010 to 2021 was assessed by measuring the IAEA-C6 and IAEA-C7 standard samples graphitized by the automated graphitization line.
William Adams (Miura Anjin) was an English navigator who sailed with a Dutch trading fleet to the far East and landed in Japan in 1600. He became a vassal under the Shogun, Tokugawa Ieyasu, was ...bestowed with a title, lands and swords, and became the first SAMURAI from England. "Miura" comes from the name of the territory given to him and "Anjin" means "pilot". He lived out the rest of his life in Japan and died in Hirado, Nagasaki Prefecture, in 1620, where he was reportedly laid to rest. Shortly after his death, graveyards designated for foreigners were destroyed during a period of Christian repression, but Miura Anjin's bones were supposedly taken, protected, and reburied. Archaeological investigations in 1931 uncovered human skeletal remains and it was proposed that they were those of Miura Anjin. However, this could not be confirmed from the evidence at the time and the remains were reburied. In 2017, excavations found skeletal remains matching the description of those reinterred in 1931. We analyzed these remains from various aspects, including genetic background, dietary habits, and burial style, utilizing modern scientific techniques to investigate whether they do indeed belong to the first English SAMURAI.
The Carrington event of 1859 has been the strongest solar flare in the observational history. It plays a crucial role in shedding light on the frequency and impacts of the past and future Solar ...Energetic Particle (SEP) events on human societies. We address the impact of the Carrington event by measuring tree‐ring 14C with multiple replications from high‐latitude locations around the event and by comparing them with mid‐latitude measurements. A transient offset in 14C following the event is observed with high statistical significance. Our state‐of‐the‐art 14C production and transport model does not reproduce the observational finding, suggesting features beyond present understanding. Particularly, our observation would require partially fast transport of 14C between the stratosphere and troposphere at high latitudes. The observation is consistent with the previous findings with the SEP events of 774 and 993 CE for which faster integration of 14C into tree rings is observed at high latitudes.
Plain Language Summary
Strong Earth‐directed solar eruptions can cause 14C concentration spikes in the atmosphere. Large enough events may leave a signal in the annually grown tree‐rings as they capture the isotopic carbon fingerprint through photosynthesis. Such rapid 14C increases have been detected, for instance, starting in years 774 and 993 CE. However, no increase has been observed following the Carrington event of 1859, despite it being the largest solar eruption of the modern era. Notably, all prior 14C measurements covering the Carrington event come from mid‐latitude trees. To achieve a broader geographical coverage, we have measured the event from several high‐latitude locations. After comparing the high‐ and mid‐latitude measurements, we have found a statistically significant difference lasting for several years post‐Carrington. To better understand the difference, we have adopted a 14C production and atmospheric transport model capable of simulating regional differences. Despite the improved model, we found it unable to reproduce the observational results, which suggests features beyond current understanding. Ultimately, the observation emphasizes the role of subtle 14C differences in tree‐ring 14C studies, potentially opening new ways to study past solar phenomena and atmospheric dynamics.
Key Points
A transient offset in 14C from high‐latitude Finnish Lapland tree rings was observed between years 1861 and 1863
The Carrington event and the stratosphere‐troposphere dynamics are discussed as potential explanations for the disparity
The discovery underscores the importance of transient offsets, high‐latitude tree rings in spotting anomalous solar/geomagnetic phenomena
Two sediment cores were collected from two sites in Nagatsura-Ura Lagoon, the mouth of which was destroyed in the 2011 Tohoku-oki tsunami. Although sediment conditions differed widely between the ...central and inner parts of the lagoon, we could identify traces of the 2011 Tohoku-oki tsunami at both, and those of earlier tsunamis in the inner part of the lagoon. Chlorophyll
a
maxima were observed at core depths between 62 and 72 cm in the central part of the lagoon. We inferred that this horizon correlated with the 2011 Tohoku-oki tsunami deposit. In the inner part of the lagoon, the horizon at core depths of 116—142 cm could be aged to the 1400s, and is thus thought to have been formed as a consequence of the Kyotoku earthquake of 1454. The dinoflagellate
Alexandrium
spp. accounted for ~ 22.6% of the total read numbers of phytoplankton from next generation sequencing. Diatoms made up the second largest group of phytoplankton, with
Chaetoceros
spp. representing ~ 10.5% of the total. The vertical profiles of dinoflagellate and diatom compositions showed little change. Although traces of tsunamis were observed in cores from the lagoon, and in nearby closed bays, we believe that the microbial composition has changed only slightly in the lagoon due to poor seawater exchange through the closed lagoon mouth.
BACKGROUNDThe Teotihuacan civilisation was the largest one in ancient Mesoamerica. The Teotihuacan city was born in the north-eastern Basin of Mexico around the second century BC, reached its peak in ...the fourth century AD, and had cultural influence throughout Mesoamerica. At its peak, the size of the city reached more than 20 km2, and the total population is estimated to have increased from 100,000 to 200,000. However, knowledge of the genetic background of the Teotihuacan people is still limited.AIMWe aimed to determine the mitogenome sequences of the Teotihuacan human remains and compare the ancient and present Mesoamericans. In addition, we aimed to identify the food habits of ancient Teotihuacans.SUBJECTS AND METHODSWe determined the mitogenome sequences of human remains dated to 250-636 cal AD using target enrichment-coupled next generation sequencing. We also performed stable isotope analysis.RESULTSWe successfully obtained nearly full-length sequences newly unearthed from a civilian dwelling in the Teotihuacan site. Teotihuacan mitochondrial DNA was classified into the haplogroups in present and ancient Mesoamericans. In addition, Teotihuacan individuals had a diet dependent on C4 plants such as maize.CONCLUSIONGenetic diversity varied among the Teotihuacans.
Celotno besedilo
Dostopno za:
DOBA, FSPLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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