Causes of an ad 774–775 14C increase

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Arising from F. Miyake, K. Nagaya, K. Masuda & T. Nakamura Nature 486, 240242 (2012)

Atmospheric 14C production is a potential window into the energy of solar proton and other cosmic ray events. It was previously concluded that 14C results from ad 774–775 would require solar events that were orders of magnitude greater than known past events1. We find that the coronal mass ejection energy based on 14C production is much smaller than claimed in ref. 1, but still substantially larger than the maximum historical Carrington Event of 18592, 3, 4. Such an event would cause great damage to modern technology5, 6, and in view of recent confirmation of superflares on solar-type stars7, 8, this issue merits attention.


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  1. Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA

    • Adrian L. Melott
  2. Department of Physics and Astronomy, Washburn University, Topeka, Kansas 66621, USA

    • Brian C. Thomas


A.L.M. planned and wrote the paper with the assistance of B.C.T. B.C.T. performed the atmospheric computations and made the plot.

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