研究者詳細 - 三宅　芙沙

論文 - 三宅　芙沙

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No signature of extreme solar energetic particle events in high-precision <SUP>14</SUP>C data from the Alaskan tree for 1844-1876 CE 招待有り査読有り

Miyake, F; Hakozaki, M; Hayakawa, H; Nakano, N; Wacker, L

JOURNAL OF SPACE WEATHER AND SPACE CLIMATE 13 巻 2023年12月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Space Weather and Space Climate

Cosmogenic nuclides - 14C from tree rings and 10Be and 36Cl from ice cores serve as an effective proxy for past extreme solar energetic particle (SEP) events. After identifying the first signature of an extreme SEP event in 774 CE, several candidates have been found in these proxy archives, such as 993 CE, 660 BCE, and 7176 BCE. Their magnitudes have been estimated to be tens of times larger than that of the largest SEP event ever observed since the 1950s. Although a detailed survey of such extreme SEP events is ongoing, the detection of intermediate-sized SEP events that bridge the gap between modern observations and extreme events detected in cosmogenic nuclides has not progressed sufficiently, primarily because of the uncertainties in cosmogenic nuclide data. In this study, we measured 14C concentrations in tree rings in the 19th century (1844- 1876 CE) to search for any increases in 14C concentrations corresponding to intermediate-size extreme SEP events. We utilized Alaskan tree-ring samples cut into early and latewoods to suppress the potential seasonal variations in intra-annual 14C data. Notably, no significant 14C variations were observed between early and latewoods (0.0 ± 0.3°), and the annual resolution 14C data series displayed an error of ~ 0.8°. Over the entire study period, no significant increase in 14C concentrations characterized by other candidates of extreme SEP events such as the 774 CE event was detected in the annual 14C data. The present result imposes a constraint on the SEP fluence when the largest class of recorded solar storms occurred (especially those in 1859 CE and 1872 CE).

DOI： 10.1051/swsc/2023030

Extreme Solar Events: Setting up a Paradigm 査読有り

Usoskin, I; Miyake, F; Baroni, M; Brehm, N; Dalla, S; Hayakawa, H; Hudson, H; Jull, AJT; Knipp, D; Koldobskiy, S; Maehara, H; Mekhaldi, F; Notsu, Y; Poluianov, S; Rozanov, E; Shapiro, A; Spiegl, T; Sukhodolov, T; Uusitalo, J; Wacker, L

SPACE SCIENCE REVIEWS 219 巻 ( 8 ) 2023年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Space Science Reviews

The Sun is magnetically active and often produces eruptive events on different energetic and temporal scales. Until recently, the upper limit of such events was unknown and believed to be roughly represented by direct instrumental observations. However, two types of extreme events were discovered recently: extreme solar energetic particle events on the multi-millennial time scale and super-flares on sun-like stars. Both discoveries imply that the Sun might rarely produce events, called extreme solar events (ESE), whose energy could be orders of magnitude greater than anything we have observed during recent decades. During the years following these discoveries, great progress has been achieved in collecting observational evidence, uncovering new events, making statistical analyses, and developing theoretical modelling. The ESE paradigm lives and is being developed. On the other hand, many outstanding questions still remain open and new ones emerge. Here we present an overview of the current state of the art and the forming paradigm of ESE from different points of view: solar physics, stellar–solar projections, cosmogenic-isotope data, modelling, historical data, as well as terrestrial, technological and societal effects of ESEs. Special focus is paid to open questions and further developments. This review is based on the joint work of the International Space Science Institute (ISSI) team #510 (2020–2022).

DOI： 10.1007/s11214-023-01018-1

その他リンク： https://link.springer.com/article/10.1007/s11214-023-01018-1/fulltext.html

Regional Differences in Carbon-14 Data of the 993 CE Cosmic Ray Event 査読有り

Miyake, F; Hakozaki, M; Kimura, K; Tokanai, F; Nakamura, T; Takeyama, M; Moriya, T

FRONTIERS IN ASTRONOMY AND SPACE SCIENCES 9 巻 2022年7月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Frontiers in Astronomy and Space Sciences

Cosmogenic nuclides such as 14C from tree rings and 10Be and 36Cl from ice cores are excellent proxies for the past extremely large solar energetic particle (SEP) events, which are dozens of times larger than the largest SEP event in the history of observation. So far, several rapid 14C increases have been discovered, which are considered to have originated from extreme SEP events (or set of successive SEP events) from verifications using multiple cosmogenic nuclide analyses in natural archives. Although these events are characterized by a rapid increase in cosmogenic nuclide concentrations, 14C data recorded worldwide do not always show similar variations, especially during the 993 CE event, where a rapid increase was recorded in either 992–993 CE or 993–994 CE in several records. We present new 14C data of the Japanese cedar sample for the 993 CE event. Although the latest data show no significant increase in 1 year, an overall increase pattern is consistent with the previously reported 14C data of the Japanese cedar, which supports that a significant 14C increase occurred from 993 to 994 CE in the Japanese sample. Given the dominant 14C production in high latitudes by SEPs, the difference in timing of increase may be a transport effect in the atmosphere. Moreover, the difference in the timing of the 14C increase can cause a 1-year age-determination error using the 993 CE radiocarbon spike. Compared with the 14C data between tree samples from high latitude and midlatitude, including Japan, high-latitude data can capture 14C changes originating from SEP events more quickly and clearly and may be more suitable for a SEP event exploration in the past.

DOI： 10.3389/fspas.2022.886140

A Single-Year Cosmic Ray Event at 5410 BCE Registered in <SUP>14</SUP>C of Tree Rings 査読有り国際共著国際誌

Miyake, F; Panyushkina, IP; Jull, AJT; Adolphi, F; Brehm, N; Helama, S; Kanzawa, K; Moriya, T; Muscheler, R; Nicolussi, K; Oinonen, M; Salzer, M; Takeyama, M; Tokanai, F; Wacker, L

GEOPHYSICAL RESEARCH LETTERS 48 巻 ( 11 ) 頁： e2021GL093419 2021年6月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Geophysical Research Letters

The annual 14C data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle (SEP) events in the past. Signatures of extreme SEP events have been reported in 774/775 CE, 992/993 CE, and ∼660 BCE. Here, we report another rapid increase of 14C concentration in tree rings from California, Switzerland, and Finland around 5410 BCE. These 14C data series show a significant increase of ∼6‰ in 5411–5410 BCE. The signature of 14C variation is very similar to the confirmed three SEP events and points to an extreme short-term flux of cosmic ray radiation into the atmosphere. The rapid 14C increase in 5411/5410 BCE rings occurred during a period of high solar activity and 60 years after a grand 14C excursion during 5481–5471 BCE. The similarity of our 14C data to previous events suggests that the origin of the 5410 BCE event is an extreme SEP event.

DOI： 10.1029/2021GL093419

THE INTCAL20 NORTHERN HEMISPHERE RADIOCARBON AGE CALIBRATION CURVE (0-55 CAL KBP) 査読有り国際共著国際誌

Reimer, PJ; Austin, WEN; Bard, E; Bayliss, A; Blackwell, PG; Ramsey, CB; Butzin, M; Cheng, H; Edwards, RL; Friedrich, M; Grootes, PM; Guilderson, TP; Hajdas, I; Heaton, TJ; Hogg, AG; Hughen, KA; Kromer, B; Manning, SW; Muscheler, R; Palmer, JG; Pearson, C; van der Plicht, J; Reimer, RW; Richards, DA; Scott, EM; Southon, JR; Turney, CSM; Wacker, L; Adolphi, F; Büntgen, U; Capano, M; Fahrni, SM; Fogtmann-Schulz, A; Friedrich, R; Köhler, P; Kudsk, S; Miyake, F; Olsen, J; Reinig, F; Sakamoto, M; Sookdeo, A; Talamo, S

RADIOCARBON 62 巻 ( 4 ) 頁： 725 - 757 2020年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Radiocarbon

Radiocarbon (C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.

DOI： 10.1017/RDC.2020.41

Prolonged production of <SUP>14</SUP>C during the ∼660 BCE solar proton event from Japanese tree rings 査読有り国際誌

Sakurai, H; Tokanai, F; Miyake, F; Horiuchi, K; Masuda, K; Miyahara, H; Ohyama, M; Sakamoto, M; Mitsutani, T; Moriya, T

SCIENTIFIC REPORTS 10 巻 ( 1 ) 頁： 660 - 660 2020年1月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

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 originate from extreme solar proton events (SPEs). Another rapid 14C increase, also known as the ca. 660 BCE event in German oak tree rings as well as increases of 10Be and 36Cl in ice cores, was presumed similar to the 775 CE event; however, as the 14C 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 14C concentrations in tree rings around 660 BCE, we have precisely measured the 14C concentrations of earlywoods and latewoods inside the annual rings of Japanese cedar for the period 669–633 BCE. Based on the feature of 14C production rate calculated from the fine measured profile of the 14C concentrations, we found that the 14C rapid increase occurred within 665–663.5 BCE, and that duration of 14C 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.

DOI： 10.1038/s41598-019-57273-2

<SUP>10</SUP>Be Signature of the Cosmic Ray Event in the 10th Century CE in Both Hemispheres, as Confirmed by Quasi-Annual <SUP>10</SUP>Be Data From the Antarctic Dome Fuji Ice Core 査読有り国際誌

Miyake, F; Horiuchi, K; Motizuki, Y; Nakai, Y; Takahashi, K; Masuda, K; Motoyama, H; Matsuzaki, H

GEOPHYSICAL RESEARCH LETTERS 46 巻 ( 1 ) 頁： 11 - 18 2019年1月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Geophysical Union ({AGU})

Cosmogenic nuclides are good indicators of past cosmic ray events and variations. To verify such phenomena, it is important to evaluate them using multiple nuclides from different archives. The cosmic ray event in 993–994 Common Era (CE) has already been confirmed with 14C and 10Be data, which show rapid increases in the concentrations. However, the 10Be data were obtained from the Greenland ice cores in the Northern Hemisphere. To investigate the extent of the 10Be increase in the Southern Hemisphere, we measured quasi-annual 10Be concentrations between 980 and 1,011 CE in the Antarctic Dome Fuji ice core. We observed a ~50% increase in 10Be concentration around 994 CE, consistent with the Greenland data. Increases in 10Be concentrations in both hemispheres support a solar origin of the 994-CE event. In addition, we propose a method of evaluating the so-called “system effect” for 10Be deposition by extracting common components from 10Be and Na+ data.

DOI： 10.1029/2018GL080475

Tree rings reveal globally coherent signature of cosmogenic radiocarbon events in 774 and 993 CE 査読有り国際誌

Buntgen, U; Wacker, L; Galvan, JD; Arnold, S; Arseneault, D; Baillie, M; Beer, J; Bernabei, M; Bleicher, N; Boswijk, G; Brauning, A; Carrer, M; Ljungqvist, FC; Cherubini, P; Christl, M; Christie, DA; Clark, PW; Cook, ER; D'Arrigo, R; Davi, N; Eggertsson, O; Esper, J; Fowler, AM; Gedalof, Z; Gennaretti, F; Griessinger, J; Grissino-Mayer, H; Grudd, H; Gunnarson, BE; Hantemirov, R; Herzig, F; Hessl, A; Heussner, KU; Jull, AJT; Kukarskih, V; Kirdyanov, A; Kolar, T; Krusic, PJ; Kyncl, T; Lara, A; LeQuesne, C; Linderholm, HW; Loader, NJ; Luckman, B; Miyake, F; Myglan, VS; Nicolussi, K; Oppenheimer, C; Palmer, J; Panyushkina, I; Pederson, N; Rybnicek, M; Schweingruber, FH; Seim, A; Sigl, M; Sidorova, O; Speer, JH; Synal, HA; Tegel, W; Treydte, K; Villalba, R; Wiles, G; Wilson, R; Winship, LJ; Wunder, J; Yang, B; Young, GHF

NATURE COMMUNICATIONS 9 巻 ( 1 ) 頁： 3605 2018年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nature Communications

Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the 14C content in 484 individual tree rings formed in the periods 770–780 and 990–1000 CE. Distinct 14C excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved 14C measurements are needed.

DOI： 10.1038/s41467-018-06036-0

SEARCH FOR ANNUAL <SUP>14</SUP>C EXCURSIONS IN THE PAST 査読有り国際誌

Miyake, F; Masuda, K; Nakamura, T; Kimura, K; Hakozaki, M; Jull, AJT; Lange, TE; Cruz, R; Panyushkina, IP; Baisan, C; Salzer, MW

RADIOCARBON 59 巻 ( 2 ) 頁： 315 - 320 2017年4月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Radiocarbon

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 annual14C excursions in the past that have yet to be confirmed. In order to detect more of these events, we measured the14C contents in bristlecone pine tree-ring samples during the periods when the rate of14C 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 anomalous14C 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.

DOI： 10.1017/RDC.2016.54

Large <SUP>14</SUP>C excursion in 5480 BC indicates an abnormal sun in the mid-Holocene 査読有り国際誌

Miyake, F; Jull, AJT; Panyushkina, IP; Wacker, L; Salzer, M; Baisan, CH; Lange, T; Cruz, R; Masuda, K; Nakamura, T

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 114 巻 ( 5 ) 頁： 881 - 884 2017年1月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Proceedings of the National Academy of Sciences of the United States of America

Radiocarbon content in tree rings can be an excellent proxy of the past incoming cosmic ray intensities to Earth. Although such past cosmic ray variations have been studied by measurements of 14C contents in tree rings with ≥10-y time resolution for the Holocene, there are few annual 14C data. There is a little understanding about annual 14C variations in the past, with the exception of a few periods including the AD 774-775 14C excursion where annual measurements have been performed. Here, we report the result of 14C measurements using the bristlecone pine tree rings for the period from 5490 BC to 5411 BC with 1- to 2-y resolution, and a finding of an extraordinarily large 14C increase (20‰) from 5481 BC to 5471 BC (the 5480 BC event). The 14C increase rate of this event is much larger than that of the normal grand solar minima. We propose the possible causes of this event are an unknown phase of grand solar minimum, or a combination of successive solar proton events and a normal grand solar minimum.

DOI： 10.1073/pnas.1613144114

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

F. Miyake, K. Masuda, T. Nakamura

Nature Communications 2013年

A signature of cosmic-ray increase in AD 774-775 from tree rings in Japan 査読有り

F. Miyake, K. Nagaya, K. Masuda, T. Nakamura

Nature 頁： 240-242 2012年

TWO NEW MILLENNIUM-LONG TREE-RING OXYGEN ISOTOPE CHRONOLOGIES (2349-1009 BCE AND 1412-466 BCE) FROM JAPAN 査読有り

Sano, M; Kimura, K; Miyake, F; Tokanai, F; Nakatsuka, T

RADIOCARBON 65 巻 ( 3 ) 頁： 721 - 732 2023年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Radiocarbon

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 d18O 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 d18O dataset currently available covers the past 4354 yr (2349 BCE to 2005 CE), which represents the longest annually resolved tree-ring d18O 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.

DOI： 10.1017/RDC.2023.29

Present status of the YU-AMS system and its operation over the past 10 years 査読有り

Takeyama, M; Moriya, T; Saitoh, H; Miyahara, H; Miyake, F; Ohyama, M; Sato, R; Shitara, R; Sakurai, H; Tokanai, F

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 538 巻頁： 30 - 35 2023年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

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.

DOI： 10.1016/j.nimb.2023.01.021

A WIGGLE-MATCHED 297-YR TREE-RING OXYGEN ISOTOPE RECORD FROM THAILAND: INVESTIGATING THE <SUP>14</SUP>C OFFSET INDUCED BY AIR MASS TRANSPORT FROM THE INDIAN OCEAN 査読有り

Sano, M; Pumijumnong, N; Fujita, K; Hakozaki, M; Miyake, F; Nakatsuka, T

RADIOCARBON 65 巻 ( 2 ) 頁： 505 - 519 2023年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Radiocarbon

Regional offsets from Northern Hemisphere radiocarbon (14C) calibration curves are widely recognized for monsoon Asia and often hinder accurate 14C dating. In this paper, we explore the possible linkage between summer monsoon intensity and 14C offsets using tree-ring δ18O and 14C data from Thailand. We developed a 297-yr floating tree-ring δ18O chronology comprising seven teak log-coffin samples from the Ban Rai rock shelter site, northwestern Thailand. The outermost ring of our chronology was estimated to date from 358-383 CE, within a 95.4% (2σ) probability range, based on a total of 10 14C measurements that were wiggle-matched against a mixed calibration curve evenly weighted from the IntCal20 and SHCal20 curves. Backward trajectory analysis showed that an intensified (weakened) summer monsoon detected in a modern tree-ring δ18O chronology was most likely to be induced by increased (decreased) air mass transport from the tropical Indian Ocean, which is an area of intense upwelling where the 14C concentration is lower than the atmospheric 14C level. However, partly because of the limited sample size and dating uncertainty, the direct linkage between the tree-ring δ18O series and 14C records obtained from our teak log-coffin samples could not be statistically verified.

DOI： 10.1017/RDC.2023.14

14C分析による過去の極端太陽面爆発の調査

三宅芙沙

日本原子力学会誌 65 巻頁： 34 - 37 2023年

過去1万年間の極端太陽高エネルギー粒子現象の調査

三宅芙沙, 箱崎真隆, Rashit Hantemiro, 早川尚志, Samuli Helama, 堀内一穂, A.J.Timothy Jull, 木村勝彦, 前原裕之, 宮原ひろ子, 森谷透, Markku Oinonen・Irina P. Panyushkina, 笹公和, 武山美麗, 門叶冬樹

第23回AMSシンポジウム報告集 2023年

Modeling the Transport and Deposition of <SUP>10</SUP>Be Produced by the Strongest Solar Proton Event During the Holocene 査読有り

Spiegl, TC; Yoden, S; Langematz, U; Sato, T; Chhin, R; Noda, S; Miyake, F; Kusano, K; Schaar, K; Kunze, M

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 127 巻 ( 13 ) 2022年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Geophysical Research: Atmospheres

Prominent excursions in the number of cosmogenic nuclides (e.g., 10Be) around 774 CE/775 document the most severe solar proton event (SPE) throughout the Holocene. Its manifestation in ice cores is valuable for geochronology, but also for solar-terrestrial physics and climate modeling. Using the ECHAM/MESSy Atmospheric Chemistry (EMAC) climate model in combination with the Warning System for Aviation Exposure to SEP (WASAVIES), we investigate the transport, mixing, and deposition of the cosmogenic nuclide 10Be produced by the 774 CE/775 SPE. By comparing the model results to the reconstructed 10Be time series from four ice core records, we study the atmospheric pathways of 10Be from its stratospheric source to its sink at Earth's surface. The reconstructed post-SPE evolution of the 10Be surface fluxes at the ice core sites is well captured by the model. The downward transport of the 10Be atoms is controlled by the Brewer-Dobson circulation in the stratosphere and cross-tropopause transport via tropopause folds or large-scale sinking. Clear hemispheric differences in the transport and deposition processes are identified. In both polar regions the 10Be surface fluxes peak in summertime, with a larger influence of wet deposition on the seasonal 10Be surface flux in Greenland than in Antarctica. Differences in the peak 10Be surface flux following the 774 CE/775 SPE at the drilling sites are explained by specific meteorological conditions depending on the geographic locations of the sites.

DOI： 10.1029/2021JD035658

その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2021JD035658

High-Resolution <SUP>10</SUP>Be and <SUP>36</SUP>Cl Data From the Antarctic Dome Fuji Ice Core (∼100 Years Around 5480 BCE): An Unusual Grand Solar Minimum Occurrence? 査読有り

Kanzawa, K; Miyake, F; Horiuchi, K; Sasa, K; Takano, K; Matsumura, M; Takahashi, T; Motizuki, Y; Takahashi, K; Nakai, Y; Ohtani, K; Tada, Y; Ochiai, Y; Motoyama, H; Matsuzaki, H; Yamazaki, A; Muramatsu, Y; Yamagata, T

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 126 巻 ( 10 ) 2021年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Geophysical Research: Space Physics

Cosmogenic nuclides in tree rings and polar ice cores record the information of past cosmic ray intensities and solar activities. A large 14C increase over 10 years has been discovered around 5480 BCE. The 14C variations in this event differ from those of other short-term cosmic ray events and typical grand solar minima. To elucidate the cause of the 14C increase around 5480 BCE, we measured the 10Be and 36Cl concentrations in the Antarctic Dome Fuji ice core at quasi-annual and 4–5 years resolutions, respectively. Based on the combined 14C, 10Be, and 36Cl data, the 5480 BCE event was probably not caused by a solar proton event (SPE) or a gamma-ray event, because the 36Cl concentration did not significantly increase as expected in these events. The incremented 10Be data were enhanced similarly to those of recent grand solar minima, but more rapidly increased (over ∼10 years). These results suggest that an unusual grand solar minimum occurred around 5480 BCE, characterized by a rapidly decreasing solar activity.

DOI： 10.1029/2021JA029378

The measurement of ion-induced cloud nucleation irradiated with a 180-MeV nitrogen ion and proton beams at HIMAC accelerator facility

Suzuki A., Itow Y., Sako T., Nakayama T., Masuda K., Miyake F., Matsumi Y., Miura K., Kusano K.

Proceedings of Science 358 巻 2021年7月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Proceedings of Science

Ion-induced nucleation by cosmic rays influenced by solar modulation is of interest, and several studies with radioactive sources or accelerator beams have been performed. We focused on ionization with high-linear energy transfer (LET) particles, such as protons, neutrons, and ions, in secondary cosmic rays and the ion density of the secondary cosmic rays near the ground using the excel-based program for calculating atmospheric cosmic-ray spectrum (EXPACS). According to the calculation, not only muons but also protons and neutrons leave substantial traces of solar modulation at an altitude of 3 km from the ground. To verify the ion-induced nucleation by these secondary high-LET cosmic rays, a chamber experiment was conducted at the accelerator facility HIMAC. Using a chamber with a capacity of 75 L, experiments were conducted by irradiating protons and nitrogen ion beams with a constant energy of 180 MeV/u with varying intensity. The experimental results confirm that the ion density and aerosol density increased as the beam intensity increased. The aerosol density was found to be proportional to the ion density, but irrelevant to the ionization density. It was concluded that the ion-induced nucleation by high-LET secondary cosmic rays, such as protons and neutrons, provides no evidence of enhancement owing to ionization density and cannot account for the claimed variation of cloud formation due to the solar modulation.

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