Ilya Usoskin

Reassessment of a cosmic ray increase event in 1279/1280 CE using carbon-14 records of tree rings.

Extreme solar energetic particle events (ESPEs) rarely occur on the Sun, as known from cosmogenic isotope proxies, the primary being 14C measured in tree rings. Several such events have been identified in tree-ring 14C data as sharp spikes. The most recent spike, around 1279 CE,...