Living with the star: Carbon-14 excursions in tree rings as the evidence for extreme solar activity

The annual ¹⁴C data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle events (SEP, also called SPE -solar particle event) in the past. Signatures of extreme SEP events have been reported in 774/775CE, 992/993 CE, and ~660 BCE. These solar storms are much stronger than the two largest directly observed SEP events: Carrington event and 23 February 1956. Here, we outline the history of SEP discovery in C14 tree-ring signatures and present other events of rapid change in C14 production over the last 8000 years (5480 BCE, 5410 BCE, 1528 BCE, 810 BCE, 1279 CE, ~1055 CE), whose origins are not known and understood yet. Applications of these C14 excursions to climate, geochronology, and archaeology will be highlighted. Comments and opinions on these and other possible applications from the audience will be welcomed.