Earth's magnetic field normally protects the surface of the planet from some storms. In 1859, the planet's defenses were totally overwhelmed. Over the past decade, similar but less powerful storms have likewise busted through, giving scientists insight into what will eventually happen again.

The outlook is not rosy.

Will an enormous solar storm hit Earth?

The solar storm of 1859 was three times more powerful than one that cut power to an entire Canadian province in 1989. Experts say if it happened today — and it could — the result might be unthinkable.

If a storm that severe occurred today, it could cause up to $2 trillion in initial damages by crippling communications on Earth and fueling chaos among residents and even governments in a scenario that would require four to 10 years for recovery,according to a report earlier this year by the National Academy of Sciences. For comparison, hurricane Katrina inflicted somewhere between $80 billion and $125 billion in damage.

Solar storm prediction

The good news is that astronomers know what they're dealing with a little more nowadays and have the ability to forecast solar storms, with the help of sun-watching spacecraft. The storms originate — still largely unpredictably — from dark sunspots. Once the spots erupt, an initial wave of radiation strikes Earth in just minutes. The worst eruptions unleash another cloud of charged particles that billow outward and take anywhere from 18 to 36 hours to reach us; those can be spotted and evaluated on the way, allowing for relatively accurate predictions of arrival time and potency.

Advance warning allows key power-grid switching stations to be turned off for protection. Satellites that might otherwise be knocked out by an electrical short are put into sleep mode.

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