Discovery of a large cosmic ray increase in 5410 BCE

2021-06-04

International research group, involving Prof. Fusa Miyake and Kayo Kanzawa of the Cosmic-Ray Division, discovered a signature of cosmic-ray increase from 5411 BCE to 5410 BCE by analyzing carbon-14 in tree rings from California, Finland, and Switzerland.
 Carbon-14 is usually produced by galactic cosmic rays which have an origin of outside the solar system, but also produced by solar energetic particles (SEPs) originates from solar eruptions such as a solar flare and a coronal mass ejection. It’s considered that extreme SEP events whose scale is far from the largest SEP event on record were occurred in 775 CE, 993 CE, and ~660 BCE from carbon-14 data of tree-rings. The similarity of the carbon-14 variation of the newly discovered 5410 BCE event with three other events (Figure 1) suggest the origin of the 5410 BCE event is an extreme SEP event. Since such a large cosmic ray increase can be recorded in not only tree-rings but also ice sheets, further application as a time marker to the research field of age dating and stratigraphy can be expected.
 The research result was published in Geophysical Research Letters.

Figure 1：Carbon-14 variation of the newly discovered 5410 BCE cosmic-ray event and already known three events in 775 CE, 993 CE, and ~660 BCE.

[Paper information]
Journal：Geophysical Research Letters
Title：A single-year cosmic ray event at 5410 BCE registered in 14C of tree rings Authors：F. Miyake, I. P. Panyushkina, A.J. T. Jull, F. Adolphi, N. Brehm, S. Helama, K. Kanzawa, T. Moriya, R. Muscheler, K. Nicolussi, M. Oinonen, M. Salzer, M. Takeyama, F. Tokanai, L. Wacker
DOI：https://doi.org/10.1029/2021GL093419
Research Spotlight by EOS: https://eos.org/research-spotlights/tree-rings-show-record-of-newly-identified-extreme-solar-activity-event