Terrestrial effects of possible astrophysical sources of an AD 774-775 increase in 14C production
Article first published online: 26 MAR 2013
©2013. American Geophysical Union. All Rights Reserved.
Geophysical Research Letters
Volume 40, Issue 6, pages 1237–1240, 28 March 2013
How to Cite
2013), Terrestrial effects of possible astrophysical sources of an AD 774-775 increase in 14C production, Geophys. Res. Lett., 40, 1237–1240, doi:10.1002/grl.50222., , , and (
- Issue published online: 27 APR 2013
- Article first published online: 26 MAR 2013
- Accepted manuscript online: 12 FEB 2013 10:24AM EST
- Manuscript Revised: 4 FEB 2013
- Manuscript Accepted: 4 FEB 2013
- Manuscript Received: 8 JAN 2013
- solar proton event;
 We examine possible sources of a substantial increase in tree ring 14C measurements for the years AD 774-775. Contrary to claims regarding a coronal mass ejection (CME), the required CME energy is not several orders of magnitude greater than known solar events. We consider solar proton events (SPEs) with three different fluences and two different spectra. The data may be explained by an event with fluence about one order of magnitude beyond the October 1989 SPE. Two hard spectrum cases considered here result in moderate ozone depletion, so no mass extinction is implied, though we do predict increases in erythema and damage to plants from enhanced solar UV. We are able to rule out an event with a very soft spectrum that causes severe ozone depletion and subsequent biological impacts. Nitrate enhancements are consistent with their apparent absence in ice core data. The modern technological implications of such an event may be extreme, and considering recent confirmation of superflares on solar-type stars, this issue merits attention.