Verification of the Cosmic Ray Event in AD 993–994 by Using a Japanese Hinoki Tree

Abstract

A rapid yearly increase in the radiocarbon content has been detected for the period from AD 993 to 994. However, this event is supported by the ¹⁴C measurements of only one cedar tree sample, and verification is necessary to confirm this event more reliably. For this purpose, this study measured the ¹⁴C content in Japanese Hinoki tree rings corresponding to the period from AD 988 to 997 using the accelerator mass spectrometry system at Yamagata University (YU-AMS). The result shows a significant ¹⁴C increase from AD 993 to 994, and is consistent with the previously measured data for the Japanese cedar tree. This marks the second case detecting an increased ¹⁴C level corresponding to the AD 994 event.

DOI: 10.2458/56.17769