Above, images of the largest coronal mass ejection ever recorded, racing from the Sun’s surface at 2,200 miles per second, on July 23, 2012.
It was the biggest geomagnetic storm in recorded history. The eruption sent 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.
Scientists say it is impossible to predict when the next monster solar storm will erupt — and equally important, whether Earth will lie in its path. What they do know is that with more sunspots come more storms, and this fall the Sun is set to reach the crest of its 11-year sunspot cycle.
Sunspots are regions of turbulentmagnetic fields where solar flares originate. Their ebb and flow have been observed for centuries, but only in the past few decades have solar scientists figured out that magnetic fields within the spots can unleash the bright bursts of light called solar flares and the giant eruptions of charged particles known as coronal mass ejections.
Experts are divided on the earthly consequences of a cataclysmic solar eruption, known as a Carrington event, for the British amateur astronomer who documented the 1859 storm.
A continentwide blackout would affect many millions of people, “but it’s manageable,” said John Moura of the North American Electric Reliability Corporation, a nonprofit group founded by utilities to help manage the power grid. Most of the grid could be brought back online within a week or so, he said.
Others are more pessimistic. They worry that a huge and well-aimed eruption from the Sun would cause not only the lights to go out, but would also damage transformers and other critical components of the grid.