Updated: NASA intensified the severity of its space weather predictions, and this story was updated to reflect them on July 12, 2012 at 7:15 p.m. EDT.

A giant solar flare shot out of a sunspot Thursday, hitting Earth with a powerful burst of X-ray and ultraviolet radiation. Solar researchers expect a moderate geomagnetic storm to follow and strike Earth this weekend, causing satellite glitches, power disruptions and colorful auroras possibly as far south as Washington D.C.

At 12:11 p.m. EDT, the flare began unleashing about a billion hydrogen bombs’ worth of energy. Radiation temporarily jammed some radio frequencies for about an hour.

Right behind the flare is a belch of solar atmosphere called a coronal mass ejection, or CME, which is now traveling toward Earth at about 3 million mph. The resulting solar storm at Earth, which NASA predicts will be a G2 to G4 (on a scale of one to five), should start Saturday morning and conclude by Sunday’s end.

“It’s the biggest of the summer so far,” said heliophysicist Alex Young of NASA’s Goddard Space Flight Center. “This could produce auroras as far south as northern California and Alabama [and] into central UK and Europe or southern New Zealand.”

“At its worst it could lead to some intermittent satellite/radio navigation problems, surface charging on satellites and power grid fluctuations,” Young wrote in an email to Wired. “But the larger storm is less likely, these are just rough estimates.”

Every solar cycle, which is an 11-year period that ramps up activity toward the end, produces between 150 and 180 large flares and related CMEs. This year has been one of the most active in recorded space weather with a flare almost four times larger striking a glancing blow to Earth in March.

If and when a solar megastorm hits Earth — and there’s a 1-in-8 chance by 2020 — the outcome would be much different. A powerful CME could temporarily peel away a significant portion of Earth’s protective magnetic shield, exposing satellites, power grids and other electronics to disruptive magnetic fields and radiation.

“We have more to expect from the sun through late 2013, perhaps through the beginning of 2014,” Young said. “That’s when we’ll reach solar maximum and see we’ll continue to see more solar eruptions.”

Image: An orbiting spacecraft called the Solar Dynamics Observatory captured this view of the sun about an hour before it launched an X-class solar flare. The purple coloring shows the strength of magnetic fields of the sun. (NASA/SDO/AIA) [high-res]
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