Isotopic terrestrial imprints of solar superflares

Abstract

The extreme cosmic event that occurred in AD 775 was detected using 14C measurements in tree rings and 10Be, 36Cl abundances in polar ice cores. Perhaps it is the most powerful solar proton event in the past several thousands of years. Simulation of isotope production with the spectra of solar flares observed in the modern era (23.02.56, 04.08.72 etc.) showed that to produce the measured amount of radionuclides, the particle fluence in the AD 775 event has to be by tens - hundreds times greater than the modern powerful solar events. The results of calculations of long-lived cosmogenic radionuclides (14C, 10Be, 36Cl) production in the Earth's atmosphere are presented.