With a peak in the cycle of solar flares approaching, U.S. electricity regulators are weighing their options for protecting the nation's grid from the sun's eruptions. They are studying the impact of historic sunstorms as far back as 1859. Among the events they are examining is the Canadian power outage of 1989. On March 13 of that year, five major electricity-transmission lines in Quebec went on the fritz. Less than two minutes later, much of the province was in the dark. The cause: A storm of charged particles from the sun had showered Earth, damaging electrical gear as far away as New Jersey. The sun is expected to hit a peak eruption period in 2013, and while superstorms don't always occur in peak periods, some warn of a disaster. John Kappenman, a consultant and former power engineer who has spent decades researching the storms, says the modern power grid isn't hardened for the worst nature has to offer. He says an extreme storm could cause blackouts lasting weeks or months, leaving major cities temporarily uninhabitable and taking a massive economic toll. This is arguably the largest natural-disaster scenario that the nation could face," said Mr. Kappenman. The 1989 Quebec storm didn't cause widespread transformer damage and the outage ended after nine hours. But the two biggest solar storms in recorded history took place in 1859 and 1921, before the development of the modern electricity grid.

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