Solar storm buffets Earth: How protected is the US power grid?

Power-grid operators nationwide are on high alert Tuesday as gale-force geomagnetic winds from a solar storm sweep across the Earth – creating potentially dangerous electrical currents that, if severe enough, could damage the US power grid.

The impact of this solar geomagnetic storm – called a “coronal mass ejection” by scientists – is being measured by satellites orbiting the Earth. It is the strongest such storm to hit Earth since 2005.

Still, it was expected to be moderate in intensity, compared with more severe events in the past, with only mild impacts on the power grid, solar storm experts said. Peak impact was expected Tuesday between morning and late in the day, solar weather experts said.

After the flare showed up on satellite sensors Sunday, solar storm advisories were sent by the National Oceanic and Atmospheric Administration to the nation’s independent system operators that oversee regional grid reliability in the nation 10 big power markets.

Beyond problems with satellites and radio communications, power generators and transmission line operators were advised to put the portions of the grid they control in a more defensive, robust posture. The idea is to gird for the impact of billions of tons of charged solar particles striking the Earth's magnetic field at two million miles per hour.

“We do not expect an impact to the bulk power system, however utilities are monitoring their facilities, as usual, for any abnormal energy flows and are prepared to take all appropriate actions to maintain reliability of the bulk power system,” writes Kimberly Mielcarek, spokesman for the North American Electric Reliability Corporation (NERC) in an e-mail. “We’re conferring with NOAA counterparts as needed, and sharing information with the North American bulk power system reliability coordinators.”

Intense debate has swirled over the issue of solar geomagnetic storms – and what, if anything, to do about these infrequent events beyond reactive, defensive actions. Most such storms have little impact on the Earth. Only a handful have had any serious impact over the past century. Still, the US and other modern societies are more dependent on power grids than ever – and damage to the grid could be severe in some cases.

The power grid is 10 times larger than it was in 1921, when the last solar super storm hit, effectively making it a giant new antenna for geomagnetic current. A far stronger solar outburst could overload and wreck hundreds of critical high-voltage transformers nationwide, blacking out 130 million people for months and costing as much as $2 trillion, according to a 2010 Oak Ridge National Laboratory study.

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