[freebeard]

He mentions one of the four events at 774 C.E.

The Charlemagne Event of 774-775 AD Was Caused by a Solar Storm
By lenrosen4 -April 5, 2017

Modeling of the impact on the ozone layer suggested there should be evidence of changes to mean average temperatures in the northern hemisphere, a decline by as much as 4 Celsius (7.2 Fahrenheit) degrees. This could have produced polar vortices of unusual duration over Europe, Siberia, and Canada. Could this have affected spring plantings and harvests in these areas after the SEP event? Could the defeat of the Lombards have been a consequence of a climate changing event of short duration?

The authors of the paper describe a similar extreme SEP event from 993 to 994 AD. Fluctuations in Carbon 14 similar to that in 774 to 775 confirm the likelihood of a large solar proton or short gamma-ray burst emanating from the sun during that period. Historical references describe significant red auroras seen in Korea, Germany nad Ireland during 993. And further confirmation of a SEP at that time is evident in the atmospheric chemistry of ice cores.