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Multiradionuclide evidence for the solar origin of the cosmic-ray events of ᴀᴅ 774/5 and 993/4.

  • Florian Mekhaldi
  • Raimund Muscheler
  • Florian Adolphi
  • Ala Aldahan
  • Jürg Beer
  • Joseph R McConnell
  • Göran Possnert
  • Michael Sigl
  • Anders Svensson
  • Hans-Arno Synal
  • Kees C Welten
  • Thomas E Woodruff
Publishing year: 2015
Language: English
Publication/Series: Nature Communications
Volume: 6
Document type: Journal article
Publisher: Nature Publishing Group

Abstract english

The origin of two large peaks in the atmospheric radiocarbon ((14)C) concentration at AD 774/5 and 993/4 is still debated. There is consensus, however, that these features can only be explained by an increase in the atmospheric (14)C production rate due to an extraterrestrial event. Here we provide evidence that these peaks were most likely produced by extreme solar events, based on several new annually resolved (10)Be measurements from both Arctic and Antarctic ice cores. Using ice core (36)Cl data in pair with (10)Be, we further show that these solar events were characterized by a very hard energy spectrum with high fluxes of solar protons with energy above 100 MeV. These results imply that the larger of the two events (AD 774/5) was at least five times stronger than any instrumentally recorded solar event. Our findings highlight the importance of studying the possibility of severe solar energetic particle events.


  • Meteorology and Atmospheric Sciences


  • Beryllium-10 in highly-resolved natural archives: Solar variability, global synchronization and implications for paleoclimate
  • ISSN: 2041-1723
Florian Adolphi
E-mail: florian [dot] adolphi [at] geol [dot] lu [dot] se

Postdoctoral fellow

Quaternary Sciences

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