资源环境科技发展态势分析平台

We present measurements of radiocarbon in annual tree rings from the time period 980-1006 Common Era (C.E.), hereby covering the cosmic ray event in 994C.E. The new radiocarbon record from Danish oak is based on both earlywood and latewood fractions of the tree rings, which makes it possible to study seasonal variations in C-14 production. The measurements show a rapid increase of approximate to 10 from 993 to 994 C.E. in latewood, followed by a modest decline and relatively high values over the ensuing approximate to 10years. This rapid increase occurs from 994 to 995 C.E. in earlywood, suggesting that the cosmic ray event most likely occurred during the period between April and June 994 C.E. Our new record from Danish oak shows strong agreement with existing C-14 records from Japan, thus supporting the hypothesis that the 994 C.E. cosmic ray event was uniform throughout the Northern Hemisphere and therefore can be used as an astrochronological tie point to anchor floating chronologies of ancient history.