Annual variations in radiocarbon concentration: implications for space weather and chronology

In his thesis, Andrea Scifo investigates how variations in radiocarbon levels in tree rings can be used to study historical solar activity and to refine scientific dating methods. Radiocarbon is produced in the upper atmosphere when cosmic rays interact with nitrogen and is then absorbed by trees as they grow. Because tree rings form annually, they preserve a year-by-year record of atmospheric radiocarbon. Occasionally, sharp increases in radiocarbon levels, known as "Miyake Events", are observed in tree-ring records. These are thought to be caused by extreme solar storms and provide valuable insights into rare space weather events. 

Scifo examines major events in the years 774/5 and 993/4 CE and compares them with the 1859 Carrington Event, one of the most powerful solar storms in recorded history. He finds a correlation between these events and the Sun's natural activity cycle. Scifo also investigates other smaller radiocarbon anomalies, but finds that these are often difficult to distinguish from natural background fluctuations. 

Beyond identifying solar events, Scifo also evaluates how precisely tree-ring sequences can be dated using radiocarbon data. He demonstrates that modern calibration techniques, especially a statistical approach known as chi-squared testing, can match tree-ring records to calendar years with an accuracy of just a few years. Overall, the work in this thesis highlights both the potential and the limitations of using annual radiocarbon data to explore past solar activity and improve chronological frameworks in archaeology and atmospheric research.

Dissertation: https://hdl.handle.net/11370/7fc5bf98-0345-4b2a-8357-e34ed1a27ed1