"In 1859 the Sun erupted, and on Earth wires shot off sparks that shocked telegraph operators and set their paper on fire."
"It was the biggest geomagnetic storm in recorded history. The Sun hurled billions of tons of electrons and protons whizzing toward Earth, and when those particles slammed into the planet’s magnetic field they created spectacular auroras of red, green and purple in the night skies — along with powerful currents of electricity that flowed out of the ground into the wires, overloading the circuits.
If such a storm struck in the 21st century, much more than paper and wires would be at risk. Some telecommunications satellites high above Earth would be disabled. GPS signals would be scrambled. And the surge of electricity from the ground would threaten electrical grids, perhaps plunging a continent or two into darkness."