The polar vortex may be gone, but another extreme event is coming. Space weather experts say northern states may be able to see the aurora borealis, or northern lights, tonight and into Friday morning.
Such predictions are difficult, but "we're hoping," said Joe Kunches with the National Oceanic and Atmospheric Administration's Space Weather Prediction Center in Boulder, Colo. "The sun has done its part, it produced a fast, energetic eruption about the middle of the day Tuesday."
That eruption blew off a piece of the solar atmosphere that is winging its way toward Earth, said Jeffrey Newmark, a solar physicist with NASA.
The northern lights appear when atoms in the Earth's high-altitude atmosphere collide with energetic charged particles from the sun. They usually appear as shimmering green waves of light in the nighttime sky in polar latitudes. Much more rarely, they can be red and even blue.
A solar storm is when "the (sun's) magnetic field gets twisted up in a high-energy state and it relaxes, and that releases a tremendous amount of energy," Newmark said.
First there is a solar flare, a release of light and high-energy particles. The light reaches the Earth in eight minutes, the high-energy particles about an hour later, Newmark said.
At the same time, there is a "coronal mass ejection," sometimes called a solar storm. It contains billions of tons of energetic hydrogen and helium ions as well as protons and electrons ejected from the sun's surface.
It takes the Earth up to 36 hours to pass through the cloud, so it is possible the lights, weather permitting, may have been visible Wednesday night going into this morning as well, said Mark Paquette with AccuWeather in State College, Pa. The clearest skies and best viewing will be in the Northeast and the Great Lakes region, he said.
It's more likely the lights, should they appear, will be visible tonight into Friday morning, he said.
The energetic particles can affect spacecraft, communication and power grids, GPS satellites and even planes flying near the poles.
These kinds of solar storms are a normal part of the sun's activity. They ebb and flow on a roughly 11-year cycle, Newmark said.
"In July of 2012, there was a much larger event, but it was on the back side of the sun facing away from us, so we barely felt it," he said.
Copyright 2014 USA TODAY
Original headline: Aurora borealis may be visible Friday
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