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| Miyake event (774–775) | |
|---|---|
| Name | Miyake event (774–775) |
| Caption | Radiocarbon spike recorded in tree rings and corals |
| Date | 774–775 CE |
| Location | Global |
| Type | Solar proton event? / Cosmic-ray event |
| Discovered | 2012 |
| Discoverer | Fusa Miyake |
Miyake event (774–775) is a rapid, globally recorded increase in cosmogenic isotopes observed in late 8th-century archives, first identified in Japanese Fusa Miyake's dendrochronological study and subsequently confirmed across multiple proxy archives. The anomaly has stimulated interdisciplinary research involving radiocarbon dating, dendrochronology, astrophysics, and paleoclimatology, prompting reassessments of extreme solar physics risk to modern infrastructure and society.
In 2012 Fusa Miyake published a striking 1.2% increase in radiocarbon (Δ14C) in Japanese cedar tree rings, citing samples from the Koyama island region and collaborating with laboratories using AMS radiocarbon dating, which immediately linked to earlier work by Willard Libby and later calibration efforts by Hans Suess and Keith Blackwell. Subsequent replications by teams including Goslar Lab researchers, Stuiver and Reimer-style calibration groups, and international dendrochronologists studying Irish oak, German pine, Italian yew, and New Zealand kauri confirmed a synchronous pulse, prompting involvement from International Tree-Ring Data Bank, Institut für Holzphysik, and National Oceanic and Atmospheric Administration proxy programs. The discovery spurred targeted searches in coral archives, Greenland ice cores, and Antarctic ice cores, engaging institutions such as ETH Zurich and the Max Planck Institute.
Tree-ring records from geographically diverse taxa—Japanese cedar, Irish oak, German pine, and New Zealand kauri—showed a near-instantaneous Δ14C jump in rings dated to 774 CE, corroborated by independent laboratories including Oxford Radiocarbon Accelerator Unit and Swiss Federal Institute of Technology teams. Marine proxies such as Bermuda coral and Fiji coral displayed contemporaneous increases in cosmogenic isotopes like 14C and 10Be, measured by accelerator mass spectrometry groups at Lawrence Livermore National Laboratory and Princeton University. Polar ice-core analyses from Greenland GRIP and Antarctic Dome C revealed corresponding 10Be and 36Cl spikes that matched the dendrochronological chronology maintained by International Tree-Ring Data Bank crossdates, establishing a global signal documented by collaborative networks including PAGES and IUGG.
Proposed origins include an extreme solar proton event (SPE) associated with a giant solar flare or coronal mass ejection (CME), a nearby gamma-ray burst (GRB), or a transient cosmic-ray flux from a supernova or pulsar wind. Modeling by astrophysicists at NASA Goddard Space Flight Center, European Space Agency, and Harvard-Smithsonian Center for Astrophysics used modern heliophysics simulations and particle-transport codes to assess ionization yields, comparing to SPE benchmarks such as the Carrington Event of 1859 and the 1956 solar proton event. Geomagnetic latitude-dependent deposition patterns studied by NOAA and UK Met Office teams, and atmospheric chemistry modeling by NCAR and MPI Mainz constrained mechanisms via nitrate and ozone perturbation scenarios linked to ionization from high-energy protons.
Proxy evidence indicates the isotope spike was effectively global, recorded across Asia, Europe, Oceania, and North America, with coralline records in Pacific Islands and ice cores from Greenland and Antarctica showing broadly synchronous signals. Historical chronicles from Tang dynasty China, Anglo-Saxon Chronicle, and Byzantine annals have been reexamined for contemporaneous auroral reports or climatic anomalies, with some researchers noting sparse references that could relate to enhanced aurora visibility at mid-latitudes during extreme space-weather episodes. Paleoenvironmental assessments by IPCC-linked research groups suggested limited direct climatic forcing but highlighted potential perturbations to stratospheric ozone and biologically active radiation fluxes with localized ecological consequences studied by UNESCO and IUCN researchers.
High-resolution dendrochronology anchored the event to the 774–775 CE ring pair using standard crossdating protocols employed by International Tree-Ring Data Bank contributors and calibrated via IntCal radiocarbon curves revised after the discovery. Coral U/Th dating at University of Miami and Woods Hole Oceanographic Institution provided independent age control, while ice-core layer counting from Greenland Ice Sheet Project and EPICA teams supplied corroborative chronologies. Bayesian chronological modeling and wiggle-matching techniques developed in Oxford and Cambridge labs integrated AMS Δ14C series with uranium-thorium dates to refine the onset to within a single annual ring, enabling precise temporal alignment across proxies used by PAGES and IUGG consortia.
Debate persists among researchers from Princeton University, MIT, Imperial College London, and University of Tokyo regarding whether a single extreme SPE suffices to explain isotope magnitudes without violating heliophysical limits inferred from modern observations of sunspots and CME energies. Alternative explanations invoking a nearby short gamma-ray burst advanced by groups at Max Planck Institute for Astrophysics and University of Chicago face constraints from expected high-energy photon signatures and lack of supernova remnants, while proposals for atypical cosmic-ray modulation by heliosphere boundary phenomena are explored by Los Alamos National Laboratory and Johns Hopkins University modelers. Interlaboratory discrepancies in 10Be and 36Cl amplitude, discussed at meetings of AGU and EGU, fuel ongoing reassessment of deposition models and production-yield cross sections.
If attributable to an extreme solar proton event, the 774–775 episode implies that modern technological systems—satellites operated by NASA, ESA, and JAXA; power grids managed by ENTSO-E and NERC; and aviation networks coordinated by ICAO—could face catastrophic disruptions from comparable future events. The event has been used by risk analysts at World Economic Forum and National Academy of Sciences to motivate resilient infrastructure planning, updated space weather forecasting by NOAA Space Weather Prediction Center, and hardened design standards adopted by IEEE and ITU. Continued paleoarchives research by PAGES and heliophysics observations by STEREO and Solar Dynamics Observatory aim to better constrain recurrence probabilities and physical mechanisms to inform mitigation strategies embraced by UNISPACE and national space agencies.
Category:Solar events