Solar storms to spark northern lights encores

Experts predict increase in the polar sky shows

Sequels to the northern lights, like last week’s polar sky shows, are likely headed for Earth on a once-a-month basis for the next year or two, solar physics experts say.

A strong solar storm grazed Earth’s magnetic field last week, delivering beautiful auroral lights to the polar skies. The S3-class storm, on a Nation- al Oceanic and Atmospheric Administration (NOAA) scale that rises from S1 to S5, represents the opening salvo in the coming peak of outbursts over the next year or so.

“The solar cycle is increasing, and so we are going to get more storms,” says University of Michigan space weather expert Tamas Gombosi. “Once an eruption happens on the sun, even the biggest ones, we’ll have at least a day’s warning.”

The current cycle was slow in getting cranked up, Gombosi adds, but appears headed for its normal peak in 2013, part of an 11-year cycle that has been documented by astronomers for centuries. The cycle drives conditions on the sun’s surface, where superheated gas bubbles upward at temperatures near 9,940 degrees Fahrenheit. Where the sun’s magnetic field becomes tangled, cooler sunspots result, some a mere 5,000 degrees. Those sunspots are draped by strong magnetic fields that spit out solar storms, outbursts of charged particles and radiation shot into space.

“These eruptions kind of come off the sun in a cone shape, and sometimes head our way,” says Solar Dynamics Observatory scientist Phillip Chamberlin of NASA’S Goddard Space Flight Center in Greenbelt, Md. Chamberlin and colleagues quickly spotted last week’s outburst, allowing NOAA “space weather” scientists to predict both its peak time and that it would be a glancing blow, passing above Earth’s north pole. “They got it right to within seven minutes,” Chamberlin says. “That is simply amazing.”

The storm peaked Jan. 24 and disrupted highfrequency radio signals for two days, Chamberlin says.

Northern lights such as last week’s result from the charged particles in a solar storm smacking the atmosphere at high latitudes, where Earth’s magnetic field doesn’t deflect them as well.

“We’ll be seeing a lot of them,” Gombosi says, but most solar eruptions fired off by the sun are pointed away from Earth. “There are plenty of hurricanes that never come onshore and just head off into the ocean. Most solar storms are the same.”