[njslim]

A big enough solar flare, especially if the magnetic polarity is in the southward direction can cause overloads in power systems

A flare in March 1989 blacked out Quebec for number of hours overloading the lines

[Bobalu]

Carrington event 1859

[grumpygresh]

At this point even a relatively minor disturbance could trigger a calamity because everyone’s on edge.