¹⁰Be Signature of the Cosmic Ray Event in the 10th Century CE in Both Hemispheres, as Confirmed by Quasi‐Annual ¹⁰Be Data From the Antarctic Dome Fuji Ice Core

Abstract

Abstract Cosmogenic nuclides are good indicators of past cosmic ray events and variations. To verify such phenomena, it is important to evaluate them using multiple nuclides from different archives. The cosmic ray event in 993–994 Common Era (CE) has already been confirmed with 14 C and 10 Be data, which show rapid increases in the concentrations. However, the 10 Be data were obtained from the Greenland ice cores in the Northern Hemisphere. To investigate the extent of the 10 Be increase in the Southern Hemisphere, we measured quasi‐annual 10 Be concentrations between 980 and 1,011 CE in the Antarctic Dome Fuji ice core. We observed a ~50% increase in 10 Be concentration around 994 CE, consistent with the Greenland data. Increases in 10 Be concentrations in both hemispheres support a solar origin of the 994‐CE event. In addition, we propose a method of evaluating the so‐called “system effect” for 10 Be deposition by extracting common components from 10 Be and Na + data.