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Two radiocarbon (14C) excursions are caused by an increase of incoming cosmic rays on a short time scale found in the Late Holocene (AD 774–775 and AD 993–994), which are widely explained as due to extreme solar proton events (SPE). In addition, a larger event has also been reported at 5480 BC (Miyake et al. 2017a), which is attributed to a special mode of a grand solar minimum, as well as another at 660 BC (Park et al. 2017). Clearly, other events must exist, but could have different causes. In order to detect more such possible events, we have identified periods when the 14C increase rate is rapid and large in the international radiocarbon calibration (IntCal) data (Reimer et al. 2013). In this paper, we follow on from previous studies and identify a possible excursion starting at 814–813 BC, which may be connected to the beginning of a grand solar minimum associated with the beginning of the Hallstatt period, which is characterized by relatively constant 14C ages in the period from 800–400 BC. We compare results of annual 14C measurements from tree rings of sequoia (California) and cedar (Japan), and compare these results to other identified excursions, as well as geomagnetic data. We note that the structure of the increase from 813 BC is similar to the increase at 5480 BC, suggesting a related origin. We also assess whether there are different kinds of events that may be observed and may be consistent with different types of solar phenomena, or other explanations. [ABSTRACT FROM AUTHOR]

Two radiocarbon excursions (AD 774–775 and AD 993–994) occurred due to an increase of incoming cosmic rays on a short timescale. The most plausible cause of these events is considered to be extreme solar proton events (SPE). It is possible that there are other annual 14C excursions in the past that have yet to be confirmed. In order to detect more of these events, we measured the 14C contents in bristlecone pine tree-ring samples during the periods when the rate of 14C increase in the IntCal data is large. We analyzed four periods every other year (2479–2455 BC, 4055–4031 BC, 4465–4441 BC, and 4689–4681 BC), and found no anomalous 14C excursions during these periods. This study confirms that it is important to do continuous measurements to find annual cosmic-ray events at other locations in the tree-ring record. [ABSTRACT FROM AUTHOR]

Using liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS), radiocarbon concentrations were measured for wine from 8 wineries located in 7 countries in the Northern and Southern hemispheres. The 14C concentrations of ethanol and residual materials in the wine were correlated (correlation coefficient 0.82). The Δ14C measurements of wine samples from the mid-latitudes in the Northern Hemisphere were approximately 11‹ lower than the extrapolations from Schauinsland data, suggesting a local fossil fuel effect. Δ14C measurements from the wine samples from the Southern Hemisphere were higher than those from the Northern Hemisphere. The offsets of the 4 wine Δ14C measurements were significant, with values between approximately 8‹ and 15‹. Because the harvest years of the mixed grapes were estimated to be 7-12 yr older than their vintage years, this leads to a caveat when determining the 14C concentrations of the year using the wine vintage. [ABSTRACT FROM AUTHOR]

To investigate the radiocarbon concentration of atmospheric CO2 over the past few millennia in Japan, we measured the 14C age of annual rings from 3 Japanese trees with calendar dates ranging from ~2000 yr old to present, and we compared the tree-ring 14C age with the corresponding 14C age from IntCal09. In some instances, the 14C ages of the annual rings of Japanese trees are not consistent with the IntCal09 data sets. Often, the 14C ages of tree rings are older than those from IntCal09, but younger than those from the SHCal04 data sets. The average shifts in the Nagoya 14C age from IntCal09 data sets and 1σ errors were determined to be +26 ± 36, +24 ± 30, +16 ± 22, +5 ± 21, and +14 ± 22 14C yr for the intervals AD 72- 382, 589-1072, 1413-1615, 1617-1739, and 1790-1860, respectively. The Japanese Archipelago is situated near the boundary of the Intertropical Convergence Zone in summer, and the 14C concentration of atmospheric CO2 over Japan can be influenced by air masses of the Southern Hemisphere with lower 14C concentrations during periods of higher solar activity and heightened East Asian summer monsoons. Our results suggest that the Japanese Archipelago is located in a critical zone where it is difficult to calibrate the 14C age of tree-ring samples using existing calibration data sets. It should be noted that calibration of the 14C dates of Japanese samples with IntCal09 may induce additional systematic shifts of calibrated ages toward older ages by about 30 yr compared with the sample optimum calendar ages. [ABSTRACT FROM AUTHOR]

Discusses the development of a proportional scintillation x-ray imaging chamber (PSXIC) for synchrotron radiation experiments. Components of the chamber; Spatial resolution attained by a prototype PSXIC; Time-resolved imaging capability.

Abstract: The linkage between multi-decadal climate variability and activity of the sun has been long debated based upon observational evidence from a large number of instrumental and proxy records. It is difficult to evaluate the exact role of each of solar parameters on climate change since instrumentally measured solar related parameters such as Total Solar irradiance (TSI), Ultra Violet (UV), solar wind and Galactic Cosmic Rays (GCRs) fluxes are more or less synchronized and only extend back for several decades. Here we report tree-ring carbon-14 based record of 11-year/22-year solar cycles during the Maunder Minimum (17th century) and the early Medieval Maximum Period (9–10th century) to reconstruct the state of the sun and the flux of incoming GCRs. The result strongly indicates that the influence of solar cycles on climate is persistent beyond the period after instrumental observations were initiated. We find that the actual lengths of solar cycles vary depending on the status of long-term solar activity, and that periodicity of the surface air temperatures are also changing synchronously. Temperature variations over the 22-year cycles seem, in general, to be more significant than those associated with the 11-year cycles and in particular around the grand solar minima such as the Maunder Minimum (1645–1715 AD). The polarity dependence of cooling events found in this study suggests that the GCRs can not be excluded from the possible drivers of decadal to multi-decadal climate change. [Copyright &y& Elsevier]