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词条 774–775 carbon-14 spike
释义

  1. Hypotheses

  2. Frequency of similar events

  3. See also

  4. References

  5. External links

The 774–775 carbon-14 spike is an observed increase of 1.2% in the concentration of carbon-14 isotope in tree rings dated to the years 774 or 775 AD, which is about 20 times as high as the normal background rate of variation. It was discovered during a study of Japanese cedar trees, with the year of occurrence determined through dendrochronology. A surge in beryllium isotope {{chem|10|Be}}, detected in Antarctic ice cores, has also been associated with the 774–775 event.[2]

The event appears to have been global, with the same carbon-14 signal found in tree rings from Germany, Russia, the United States, and New Zealand.[2][4][5]

The signal exhibits a sharp increase of ≈1.2% followed by a slow decline (see Figure 1), which is typical for an instant production of carbon-14 in the atmosphere,[2] indicating that the event was short in duration. The globally averaged production of carbon-14 for this event is calculated as {{nowrap|1=Q = (1.1 – 1.5) × 108 atoms/cm2}}.[2][9][10]

Hypotheses

Several possible causes of the event have been considered.

{{Quote|text=Annus Domini 774. This year the Northumbrians banished their king, Alred, from York at Easter-tide; and chose Ethelred, the son of Mull, for their lord, who reigned four winters. This year also appeared in the heavens a red crucifix, after sunset; the Mercians and the men of Kent fought at Otford; and wonderful serpents were seen in the land of the South-Saxons.|author=|source=Anglo-Saxon Chronicle[1]}}

The "red crucifix" recorded by the Anglo-Saxon Chronicle was thought to have been a supernova.[1] However, since no supernova remnant has been found for this year, it is interpreted as an aurora borealis.[2]

In China, there is only one clear reference to an aurora in the mid-770s, namely the one on 12 January 776.[2][3] Instead, an anomalous "thunderstorm" was recorded for 775.[4]

The common paradigm is that the event was caused by a solar particle event (SPE), or a consequence of events as often happen, from a very strong solar flare, perhaps the strongest ever known but still within the Sun's abilities.[2][9][19][20][5]

Another discussed scenario of the event origin, involving a gamma-ray burst,[10][23] appears unlikely, since the event was also observed in isotopes {{chem|10|Be}} and {{chem|36|Cl}}.[5]

Frequency of similar events

The event of 774 is the strongest spike over the last 11,000 years in the record of cosmogenic isotopes,[19] but it is not unique. A similar event occurred in 993 or 994, but it was only 0.6 times as strong.[26] Several other events of the same kind are also suspected to have occurred during the Holocene epoch.[19]

From these statistics, one may expect that such strong events occur once per tens of millennia, while weaker events may occur once per millennium or even century. The event of 774 did not cause catastrophic consequences for life on Earth,[6][20] but had it happened in modern times, it may have produced catastrophic damage to modern technology, particularly to communication and space-borne navigation systems. In addition, a solar flare capable of producing the observed isotopic effect would pose considerable risk to astronauts.[7]

As of 2017, there is "little understanding"[8] of {{chem|14|C}} past variations because annual-resolution measurements are only available for a few periods (e.g., the AD 774–775). In 2017, another "extraordinarily large" {{chem|14|C}} increase (20‰) has been associated with the 5480 BC event, but it is not associated with a solar event because of its long duration, but rather to an unusually fast grand minimum of solar activity.[8]

In 2019, evidence of another "enormous solar storm" ~660 BC was published, comparable with the AD 774–775 and 993 events.[9] One of the conclusions of the work is that an exclusive reliance on {{chem|14|C}} records may lead to underestimation of the number of possibly catastrophic events. High-resolution measurements are needed for {{chem|14|C}}, {{chem|10|Be}} and {{chem|36|Cl}}.

See also

  • List of solar storms

References

1. ^1 {{cite web|author=Nancy Owano|title=Red Crucifix sighting in 774 may have been supernova|website=Phys.org|date=2012-06-30|url=https://phys.org/news/2012-06-red-crucifix-sighting-supernova.html}}
2. ^{{cite journal |author1=Stephenson, F. R. |title=Astronomical evidence relating to the observed 14C increases in A.D. 774-5 and 993-4 as determined from tree rings |journal=Advances in Space Research |volume=55 |issue=6 |publisher=Elsevier |doi=10.1016/j.asr.2014.12.014 |pages=1537–1545 |year=2015 |bibcode=2015AdSpR..55.1537S }}
3. ^{{cite journal |author1=Stephenson, F. R. |title=Do the Chinese Astronomical Records Dated AD 776 January 12/13 Describe an Auroral Display or a Lunar Halo? A Critical Re-examination |journal=Solar Physics |volume=294 |publisher=Solar Physics |doi=10.1007/s11207-019-1425-7 |pages=36 |year=2019 }}
4. ^{{cite journal |title= Searching for events in Chinese ancient records to explain the increase in 14C from 774–775 CE and 993–994 AD |author=Ya-Ting Chai |author2=Yuan-Chuan Zou |last-author-amp=yes | year=2015 |journal=Research in Astronomy and Astrophysics | volume= 15|issue= 9}}
5. ^1 {{cite journal | date=2015 | author=Mekhaldi | display-authors=etal | journal =Nature Communications| volume=6 | pages=8611 | doi=10.1038/ncomms9611 | title=Multiradionuclide evidence for the solar origin of the cosmic-ray events of ᴀᴅ 774/5 and 993/4|bibcode = 2015NatCo...6E8611M | pmid=26497389 | pmc=4639793}}
6. ^{{cite journal | last=Sukhodolov | first=Timofei | last2=Usoskin | first2=Ilya | last3=Rozanov | first3=Eugene | last4=Asvestari | first4=Eleanna | last5=Ball | first5=William T. | last6=Curran | first6=Mark A. J. | last7=Fischer | first7=Hubertus | last8=Kovaltsov | first8=Gennady | last9=Miyake | first9=Fusa | last10=Peter | first10=Thomas | last11=Plummer | first11=Christopher | last12=Schmutz | first12=Werner | last13=Severi | first13=Mirko | last14=Traversi | first14=Rita | title=Atmospheric impacts of the strongest known solar particle storm of 775 AD | journal=Scientific Reports | publisher=Springer Nature | volume=7 | issue=1 | pages=45257 | date=March 28, 2017 | issn=2045-2322 | doi=10.1038/srep45257 | pmid=28349934 | pmc=5368659 | display-authors=1|bibcode = 2017NatSR...745257S}}
7. ^{{Cite journal|last=Townsend|first=L. W.|last2=Porter|first2=J. A.|last3=deWet|first3=W. C|last4=Smith|first4=W. J.|last5=McGirl|first5=N. A.|last6=Heilbronn|first6=L. H.|last7=Moussa|first7=H. M.|date=2016-06-01|title=Extreme solar event of AD775: Potential radiation exposure to crews in deep space|url=http://www.sciencedirect.com/science/article/pii/S0094576515303301|journal=Acta Astronautica|series=Special Section: Selected Papers from the International Workshop on Satellite Constellations and Formation Flying 2015|volume=123|pages=116–120|doi=10.1016/j.actaastro.2016.03.002|bibcode = 2016AcAau.123..116T }}
8. ^1 {{cite journal | pmid = 28100493 | doi=10.1073/pnas.1613144114 | volume=114 | issue=5 | title=Large 14C excursion in 5480 BC indicates an abnormal sun in the mid-Holocene | pmc=5293056 | journal=Proceedings of the National Academy of Sciences of the United States of America | pages=881–884 | last1 = Miyake | first1 = F. | last2 = Jull | first2 = A. J. | last3 = Panyushkina | first3 = I. P. | last4 = Wacker | first4 = L. | last5 = Salzer | first5 = M. | last6 = Baisan | first6 = C. H. | last7 = Lange | first7 = T. | last8 = Cruz | first8 = R. | last9 = Masuda | first9 = K. | last10 = Nakamura | first10 = T.|bibcode = 2017PNAS..114..881M | year=2017 }}
9. ^{{cite journal | last = O'Hare | first = Paschal |display-authors=etal | title = Multiradionuclide evidence for an extreme solar proton event around 2,610 B.P. (∼660 BC) | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = | issue = | pages = 201815725 | date = 2019 | doi = 10.1073/pnas.1815725116|doi-access=free }}
10. ^1 2 3 4 5 6 7 {{cite journal|last1=Usoskin |first1=I. G.|last2=Kromer |first2=B.|last3=Ludlow |first3=F.|last4=Beer |first4=J.|last5=Friedrich |first5=M.|last6=Kovaltsov |first6=G. A.|last7=Solanki |first7=S. K.|last8=Wacker |first8=L.|display-authors=1|date=2013|title=The AD775 cosmic event revisited: The Sun is to blame|journal=Astronomy & Astrophysics|volume=552 |issue=1 |pages=L3|arxiv=1302.6897|bibcode=2013A&A...552L...3U|doi=10.1051/0004-6361/201321080}}
11. ^1 2 {{cite journal|last1=Thomas |first1=B. C.|last2=Melott |first2=A. L.|last3=Arkenberg |first3=K. R.|last4=Snyder |first4=B. R.|date=2013|title=Terrestrial effects of possible astrophysical sources of an AD 774–775 increase in 14C production|journal=Geophysical Research Letters|volume=40 |issue=6 |pages=1237|arxiv=1302.1501|bibcode=2013GeoRL..40.1237T|doi=10.1002/grl.50222}}
12. ^1 {{cite journal|last1 = Güttler |first1 = D.|last2 = Beer |first2 = J.|last3 = Bleicher |first3 = N.|title = The 774/775 AD event in the southern hemisphere|journal = Annual Report of the Laboratory of Ion Beam Physics|date = 2013|publisher = ETH-Zurich}}
13. ^1 {{cite journal|last1 = Jull |first1 = A.J.T.|last2 = Panyushkina |first2 = I.P.|last3 = Lange |first3 = T.E.|display-authors = etal|title = Excursions in the 14C record at AD 774–775 in tree rings from Russia and America|journal = Geophys. Res. Lett.|volume = 41|issue = 8|doi = 10.1002/2014GL059874|pages = 3004–3010|date = 2014|bibcode = 2014GeoRL..41.3004J }}
14. ^1 2 {{ cite journal|last1 = Pavlov |first1 = A.K.|last2 = Blinov |first2 = A.V.|last3 = Konstantinov |first3 = A.N.|display-authors = etal|title = AD 775 pulse of cosmogenic radionuclides production as imprint of a Galactic gamma-ray burst|journal = Mon. Not. R. Astron. Soc.|date = 2013|volume = 435|issue = 4|pages = 2878–2884|doi = 10.1093/mnras/stt1468|arxiv = 1308.1272 |bibcode = 2013MNRAS.435.2878P }}
15. ^1 2 {{cite journal|last1 = Melott |first1=A.L.|last2 = Thomas |first2=B.C.|title = Causes of an AD 774-775 C increase|journal = Nature|date = 2012|volume = 491|issue=7426|pages = E1–E2|doi = 10.1038/nature11695|arxiv = 1212.0490 |bibcode = 2012Natur.491E...1M |pmid=23192153}}
16. ^1 {{cite journal|last1 = Miyake |first1=F.|last2 = Masuda |first2=K.|last3 = Nakamura |first3=T.|title = Another rapid event in the carbon-14 content of tree rings|journal = Nature Communications|date = 2013|volume = 4|pages = 1748|doi = 10.1038/ncomms2783|bibcode = 2013NatCo...4E1748M |pmid=23612289}}
17. ^1 2 3 {{cite journal|last1 = Usoskin |first1=I.G.|last2 = Kovaltsov |first2=G.A.|title = Occurrence of Extreme Solar Particle Events: Assessment from Historical Proxy Data|journal = Astrophys. J.|arxiv = 1207.5932|date = 2012|volume = 757|issue=1|pages = 92|doi = 10.1088/0004-637X/757/1/92|bibcode = 2012ApJ...757...92U }}
18. ^1 {{cite journal|last1=Hambaryan |first1=V. V.|last2=Neuhauser |first2=R.|date=2013|title=A Galactic short gamma-ray burst as cause for the 14C peak in AD 774/5|journal=Monthly Notices of the Royal Astronomical Society|volume=430 |issue=1 |pages=32–36|arxiv=1211.2584|bibcode=2013MNRAS.430...32H|doi=10.1093/mnras/sts378}}
[10][11][12][13][14][15][16][17][18]
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External links

  • [https://www.youtube.com/watch?v=inIFO5ZvdqM YouTube SciShow Space Episode describing this event]
{{Solar storms}}{{DEFAULTSORT:774-775 carbon-14 spike}}

5 : 774|775|Geomagnetic storms|Stratigraphy|Dendrology
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