The region of the sun that erupted can still send more blasts our way, Kunches said. Another set of active sunspots is ready to aim at Earth.
"This is a big sun spot group, particularly nasty," NASA's Hathaway said. "Things are really twisted up and mixed up. It keeps flaring."
Storms like this start with sun spots. First, there's an initial solar flare of subatomic particles that resembles a filament coming out of the sun. That part usually reaches Earth only minutes after the initial burst, bringing radio and radiation disturbances. Next is the coronal mass ejection, which looks like a growing bubble and takes a couple days to reach Earth.
Solar storms have three ways they can disrupt technology on Earth: with magnetic, radio and radiation emissions. In 1989, a strong solar storm knocked out the power grid in Quebec, causing 6 million people to lose power.
For North America, the good part of a solar storm — the one that creates more noticeable auroras or Northern Lights — was likely to peak Thursday evening. Auroras were likely to dip only as far south as the northern edges of the United States, Kunches said, but a full moon would make them harder to see.
Solar storms can bring additional radiation around the north and south poles — a risk that sometimes forces airlines to reroute flights. On Thursday, Delta Air Lines and United Airlines sent 11 flights to Asia on a more southern route rather than their more common path over the Arctic. Three American Airlines flights flew lower than normal over the northernmost parts of their routes to Japan and China.
AP Business Writers Josh Freed and David Koenig contributed to this report.
NOAA Space Weather Prediction Center: www.swpc.noaa.gov
NASA on solar flare: http://www.nasa.gov/mission_pages/sunearth/news/News030712-X1.5.html
Follow Seth Borenstein at http://twitter.com/borenbears
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