Can Solar Cyclic Variability Mimic Extreme Solar Particle (Miyake) Events in Radiocarbon?

Abstract

Abstract Rapid, strong enhancements in C in the Earth's atmosphere, known as Miyake events, rarely occurred over the past millennia, pointing to major radiation storms affecting Earth. They are produced by extreme solar particle events (ESPEs) and are separated by an order‐of‐magnitude gap in the strength from directly observed solar particle storms. This leaves their physical interpretation unconstrained. To bridge this gap, weak–moderate Miyake events ought to be detected, but this possibility was previously limited by the accuracy of individual 14 C measurements. Here, we performed a sensitivity study of the detectability of a Miyake event in radiocarbon data over the background of natural C variability. The study was done for realistic conditions, including a reference ESPE, using the SOCOL:14C‐Ex (SOlar CLimate Ozone Links model, radiocarbon version for extreme solar proton events) model of carbon transport in the Earth's atmosphere. We found that background variability, such as long‐term trends and the solar cycle, can significantly distort and even mimic weak‐to‐moderate Miyake events in radiocarbon data. We conclude that reducing measurement errors alone is not sufficient to identify such weaker events. In addition, the galactic cosmic ray (GCR)‐related background should be reconstructed over ≈50 years around event candidates using high‐precision annual measurements of C.