The only hope is one can find the now obsolete computing parts needed after the last modern computer stops working. Collapse OS is a fantasy.
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...