So I just learned about this yesterday. On Sept 1st and 2nd 1859, our Sun hit the Earth with a Massive Solar Flare that caused Telegraph stations to burst into flames.
If this were to happen to us today, it would literally throw us back 200 years. Every Satellite would be destroyed, Global Power outages, etc.
They equate it to a Nuclear War, where Humans would start killing each other in less than 2 weeks trying to survive as food expires and turns us into savages.
Pretty scary stuff considering it's happened once before.
https://en.wikipedia.org/wiki/Carrington_Event