We could always fall back to running the internet with RFC1149
The flare itself is fairly fast. But the issue is charged particles that take longer to get us. And they are spread out in time.
As https://www.livescience.com/carrington-event describes, the Carrington Event was a solar flare lasting only 5 minutes. But the magnetic disturbances kept arriving over a week.
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[0] - https://en.wikipedia.org/wiki/List_of_The_Outer_Limits_(1995...
https://www.scientificamerican.com/article/solar-storms-can-...