C03_07

New records of ¹⁴C excursions at 664/62 BCE and 1279/81 CE from Inner Eurasia examine signal timing

Jull A^1,2, Panyushkina I³, Molnar M², Varga T², Livina V⁴, Sljusarenko I⁵, Myglan V⁶, Miyake F⁷

¹University Of Arizona, Tucson, United States, ²Institute for Nuclear Research, Debrecen, Hungary, ³Laboratory for Tree-Ring Research, Tucson, USA, ⁴National Physical Laboratory, Teddington, UK, ⁵Institute of Archaeology and Ethnography, Novosibirsk, Russia, ⁶Siberian Federal University, Krasnoyarsk, Russia, ⁷Institute for Space-Earth Environmental Research, Nagoya, Japan

Excursions in the annual ¹⁴C production rate in the atmosphere are manifest in an excess of up to 20 ‰ in tree rings, caused by transient increases in the ¹⁴C production rate. These signals rise rapidly over a period of 1-2 yr and has a decay time of about 15-20 yr. These events are generally explained as a rapid increase of incoming cosmic rays or gamma rays. Only a few have been reproduced in multiple tree-ring records from many locations around the globe, particularly at 7176BCE, 5259BCE, ~660BCE, 774-775CE and 993-994CE reported by different laboratories. These excursions are positively connected to the impact of strong Solar Energetic Particles (SEP) events and are also observed from ¹⁰Be and ³⁶Cl excursions in polar ice cores. Other proposed events show different structures and either coincide with Grand Solar Minima or other effects of a lesser magnitude. These include reported events at 815BCE, 5480BCE, 5410BCE, 1052/1054CE and 1279CE events. We focus on a new detailed record of the 664-662BCE event from the Altai Mountains. It appears that the intensity and structure of the ¹⁴C signal is multifaced in space and time, which complicates understanding of the forcing and attribution to the underlying astrophysical events. Timing of these events is important to register the recurrence intervals of these events for past and future ¹⁴C excursions. We investigated the time concordance of a number of these events and possible explanations.