A ​Solar ​S​uperstorm occurred in​ 774 ​AD.

[John Clark]

It's been estimated that during the next 10 years there is a 12% chance of the Earth being hit with a solar storm comparable in strength to the Carrington Event which happened on September 1, 1859  and produced  beautiful aurora displays as far south as the equator and blew up telegraph lines but otherwise caused little damage; but if something like that hit today it would short out nearly all satellites and devastate our power and communication grids which could take years to fully repair. So it would seem prudent to spend a few dollars to harden critical electronics in order to prepare for such a catastrophic Black Swan situation. The case for doing so is strengthened by an article in yesterday's issue of the journal Nature which gives evidence of a solar storm about 100 times as powerful as the Carrington Event that hit the Earth in 774 AD; there is also evidence that solar storms of a similar gigantic magnitude affected the earth in 5,259 and 7,176 BC.

Solar superstorm of AD 774 recorded subannually by Arctic tree rings

John K Clark