Researchers Identify Major 13th-Century Solar Storm Using Tree Rings and Ancient Diaries
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Scientists have pinpointed a significant solar proton event that occurred between the winter of 1200 CE and spring of 1201 CE. They combined refined carbon 14 measurements from ancient Japanese trees with medieval historical records of auroras to make the discovery. The findings, published in the Proceedings of the Japan Academy, Series B, provide new data on historical solar activity and its cycles.
Facts First
- A solar proton event was identified from 1200-1201 CE using carbon 14 trapped in buried asunaro trees from northern Japan.
- Medieval diaries and Chinese records described red auroras at low latitudes, corroborating the event.
- The event occurred at the peak of a solar cycle that was seven to eight years long, shorter than the modern eleven-year cycle.
- Researchers refined their carbon 14 measurement technique over more than a decade to achieve the necessary precision.
- Earth's magnetic field blocks most solar particles, but some enter near the poles and create atmospheric carbon 14.
What Happened
A research team from the Okinawa Institute of Science and Technology (OIST) identified evidence of a major solar proton event (SPE) that likely occurred between the winter of 1200 CE and the spring of 1201 CE. They achieved this by combining carbon 14 measurements from the rings of buried asunaro trees in Aomori Prefecture, Japan, with historical records of auroras from medieval diaries in Japan and China. The team used a carbon 14 measurement technique they spent over ten years refining and employed dendroclimatic studies to date the event precisely. The findings were published in the Proceedings of the Japan Academy, Series B.
Why this Matters to You
Understanding the frequency and intensity of past solar storms helps scientists model future risks to modern technology. While Earth's magnetic field protects the planet from most high-energy solar particles, extreme events can disrupt satellite communications, navigation systems, and power grids. This research may contribute to better predictive models, which could lead to more robust safeguards for the infrastructure you rely on daily.
What's Next
The identification of this 13th-century event provides a new data point for studying historical solar cycles. Researchers may now apply this refined method of combining precise carbon 14 measurements with historical records to search for other previously unknown solar proton events. Further study could help clarify whether the shorter, seven-to-eight-year solar cycle observed then is a recurring pattern or an anomaly, potentially improving long-term forecasts of solar activity.