A Caltech Library Service

Relationship between solar activity and Δ^(14)C peaks in AD 775, AD 994, and 660 BC

Park, Junghun and Southon, John and Fahrni, Simon and Creasman, Pearce Paul and Mewaldt, Richard (2017) Relationship between solar activity and Δ^(14)C peaks in AD 775, AD 994, and 660 BC. Radiocarbon, 59 (04). pp. 1147-1156. ISSN 0033-8222. doi:10.1017/RDC.2017.59.

[img] PDF - Published Version
Creative Commons Attribution.

[img] MS Word - Supplemental Material
Creative Commons Attribution.


Use this Persistent URL to link to this item:


Since the AD 775 and AD 994 Δ^(14)C peak (henceforth M12) was first measured by Miyake et al. (2012, 2013), several possible production mechanisms for these spike have been suggested, but the work of Mekhaldi et al. (2015) shows that a very soft energy spectrum was involved, implying that a strong solar energetic particle (SEP) event (or series of events) was responsible. Here we present Δ^(14)C values from AD 721–820 Sequoiadendron giganteum annual tree-ring samples from Sequoia National Park in California, USA, together with Δ^(14)C in German oak from 650–670 BC. The AD 721–820 measurements confirm that a sharp Δ^(14)C peak exists at AD 775, with a peak height of approximately 15‰ and show that this spike was preceded by several decades of rapidly decreasing Δ^(14)C. A sharp peak is also present at 660 BC, with a peak height of about 10‰, and published data (Reimer et al. 2013) indicate that it too was preceded by a multi-decadal Δ^(14)C decrease, suggesting that solar activity was very strong just prior to both Δ^(14)C peaks and may be causally related. During periods of strong solar activity there is increased probability for coronal mass ejection (CME) events that can subject the Earth’s atmosphere to high fluencies of solar energetic particles (SEPs). Periods of high solar activity (such as one in October–November 2003) can also often include many large, fast CMEs increasing the probability of geomagnetic storms. In this paper we suggest that the combination of large SEP events and elevated geomagnetic activity can lead to enhanced production of ^(14)C and other cosmogenic isotopes by increasing the area of the atmosphere that is irradiated by high solar energetic particles.

Item Type:Article
Related URLs:
URLURL TypeDescription
Mewaldt, Richard0000-0003-2178-9111
Additional Information:© 2017 by the Arizona Board of Regents on behalf of the University of Arizona. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (, which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Published online: 19 June 2017. This study was supported by a research project funded by the Ministry of Science, ICT and Future Planning of Korea. We are grateful for helpful and constructive comments from F Miyake and F Mekhaldi. The work at Caltech was supported by NASA under NNX13A66G, and subcontract 00008864 of NNX15AG09G, and by the NSF under grant AGS-1622487.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:660 BC, AD 775, CME (coronal mass ejection), M12, solar energetic particles (SPE)
Issue or Number:04
Record Number:CaltechAUTHORS:20170818-085536951
Persistent URL:
Official Citation:Park, J., Southon, J., Fahrni, S., Creasman, P., & Mewaldt, R. (2017). Relationship between solar activity and Δ14C peaks in AD 775, AD 994, and 660 BC. Radiocarbon, 59(4), 1147-1156. doi:10.1017/RDC.2017.59
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:80602
Deposited On:18 Aug 2017 17:23
Last Modified:15 Nov 2021 19:37

Repository Staff Only: item control page