A search for past extreme solar events using 14C data in tree rings

Abstract:

Cosmogenic nuclides such as ¹⁴C is produced by energetic particles. In recent years, annual ¹⁴Cincreases have been detected, and it is considered that the cause of these events is an extreme solar event (or succesive solar events) with a very hard energy spectrum. In order to clarify the occurrence rate of such solar event which can affect ¹⁴C variation, we conducted a continuous measurement of ¹⁴C concentrations in tree rings over the past 3000 years. In the presentation, I will discuss the characteristics of the detected events and their occurrence rate.