Study for elucidation of the 5480 BC cosmic ray event using cosmogenic nuclides 10Be and 36Cl.

Abstract

Recently, the increase of cosmic ray flux was found around 5480 BC using the ¹⁴C measurements for tree rings with 1- to 2-y resolution. It is assumed that it may be caused by the large solar flares but we cannot specify the detail cause of this event. In this study, we aim to elucidate the cause of 5480 BC cosmic ray event by measuring ¹⁰Be and ³⁶Cl in the ice core which was drilled at the Dome Fuji Station in Antarctica, and investigate the variation of cosmic ray flux around 5480 BC. The result of ³⁶Cl concentration variation using the Accelerator Mass Spectrometry (AMS) system in the University of Tsukuba is reported in this presentation. In addition, the performance of ¹⁰Be-AMS and the future plan is also presented.