Super solar particle event around AD775 was found

Abstract

A rapid radiocarbon 14C increase of 120/00 in AD774–775 has been reported in cedar and oak tree rings. So far, the origin of the 14C increase is still uncertain and the possible origin is either supernova or solar particle event. The most possible origin of 14C increase is strong solar flares and Coronal Mass Ejections (CMEs) with strong particles emission. Comprehensive approaches to identify the strong historical solar particle events based on the rapid 14C/10Be increase in tree/coral rings and ice cores, long duration strong auroras and geomagnetic storms are introduced. Evidence of the super auroras in AD775 was first found in a Chinese Chronicles Jiutangshu and it supports the views that the rapid 14C increase and strong auroras around AD775 are most possibly caused by strong solar storms with intense particles emission. It was identified that the solar event around AD775 would be the strongest solar particle event in the past 11400 years. The discovery is significant for the research on the history of solar activities, space weather and forecast, radiation of solar energetic particles and protection.