Comet encounters and carbon 14

The ¹⁴C production of shock-accelerated particles is calculated in terms of the total energy released in energetic particles. The recently reported 1.2% jump in the ¹⁴C content of the atmosphere in the year C.E. 775, it is found, would require ≳ 10³⁴ erg in energetic particles, less than first estimates but far more than any known solar flare on record. It is noted that the superflare from a large comet (comparable to C/Hale-Bopp) colliding with the sun could produce shock-accelerated GeV cosmic rays in the solar corona and/or solar wind, and possibly account for the C.E. 775 event. Several additional predictions of cometary encounters with the sun and other stars may be observable in the future.