Frank Morring, Jr. Washington

Powerful solar storms are an imperfectly understood threat to the world's power grids, but one with the potential for economic damage so catastrophic that the estimated $100-200 million it would cost annually to deploy an operational space-weather warning system could be trivial by comparison.

In a “perfect storm” scenario, when a high-power coronal mass ejection (CME) of charged particles slams into Earth at a time when the delicate balance operators try to maintain in electric power grids is precarious, the resulting damage could take a decade to repair at a cost very roughly estimated by the National Academies of Science as high as $1 trillion.

In recent congressional testimony and a public forum in Washington, space-weather experts caution that the 1859 solar storm observed by British astronomer Richard Carrington is only the most powerful one detected so far. That storm took down parts of the growing U.S. telegraph network, starting fires in the process and subjecting some telegraph operators to electric shock.

Recent calculations suggest there is a 6-12% chance of another storm at that level in any given year. But since there were no networks of long electric wires crisscrossing the planet before the 19th century, there is really no way to know precisely how bad “the Carrington event” really was, according to Tom Mahony, senior advanced systems manager at Ball Aerospace.

“We've only had 150 years to observe these events,” he says. “We're projecting this as a 100-year event when we've only observed it for 150 years. We have geological records that go back millennia.”

Solar storms, and particularly CMEs, can pose a health threat to astronauts in space and passengers on airliners passing over the poles, where protection from Earth's magnetic field is weakest. They also can damage spacecraft electronics, and increase drag on satellites so they consume more fuel to maintain their proper orbits. But the most serious potential for damage rests with the transformers that maintain the proper voltage for efficient transmission of electricity through the grid.

On Dec. 4, Mahony told a panel sponsored by the Space Enterprise Council and the George C. Marshall Institute that by National Academies' calculations, there are 2,000 ground transformers and 140 million more mounted on power poles that are vulnerable to CMEs. Under the right conditions, it is at least possible that a major CME could cause so much damage that power would be off or compromised indefinitely. Listing the resulting impacts on food and water distribution, health care and the economy, Mahony warned the results could be dire.