Doyle Rice

USA TODAY

A "strong" solar flare that launched off the sun Wednesday afternoon could cause some fluctuations in Earth's power grid and slight disturbances in satellites and radio transmissions on Friday and Saturday.

Major disruptions are not expected, even though the flare was classified as an "X-class" flare, which is at the high end of the solar flare scale. Wednesday's flare followed a weaker flare late Monday.

"We expect geomagnetic storm levels in the G2 (moderate) and G3 (strong) range," said Bill Murtagh, space weather forecaster for the National Oceanic and Atmospheric Administration.

"G2-G3 geomagnetic storms can cause some problems for the (power) grid but are typically very manageable," Murtagh said in an e-mail Thursday morning. "We may also see some anomalies with satellites so satellite operators around the world have been notified. And problems with the accuracy of GPS have been observed with this level of storming."

Forecasters with NOAA's Space Weather Prediction Center in Boulder, Colo., said the flare "caused impacts to high-frequency radio communications on Earth" Wednesday afternoon.

Intense flares such as the one that erupted Wednesday are often associated with coronal mass ejections, or "CME"s. A coronal mass ejection contains billions of tons of energetic hydrogen and helium ions as well as magnetic fields ejected from the sun's surface.

Though this CME will hit the Earth, this CME isn't big enough or impressive enough to cause a more disruptive geomagnetic storm. But "any additional eruptions in the next few days will likely produce more disturbances in our geomagnetic field," Murtagh added.

It was "fairly rare" for the two CMEs (Monday evening and midday Wednesday) to come so close in succession, said Thomas Berger, the director of the Space Weather Prediction Center

SPACE CENTRAL

At the Space Weather Prediction Center in Colorado, phones ring constantly, as scientists consult with their colleagues around the world, and with their Defense Department counterparts in Nebraska, who monitor the effects on spy satellites and other classified equipment.

Screens display images of the sun in a variety of formats, from the familiar orange-yellow we're used to seeing to otherwise invisible radiation steaming toward us. The Earth's magnetic field protects us from the worst of the impacts, but the particles also affect the field, and thus our electronics.

Forecaster Chris Smith takes a call from a Civil Air Patrol group in the Midwest wondering whether the flare will affect their planned weather balloon launch.

"You'll still be within the protection of the Earth's atmosphere, so you should be OK," Smith advises. "But if you can hold off a day, that's not a bad idea."

Depending on how strongly it hits the earth, the flare's impacts could interfere with some radio signals and slightly alter GPS readings. "Folks driving down the road wouldn't notice much difference," said Murtagh.

NIGHT LIGHTS

One nice side effect of the solar storm is an expansion of the photogenic aurora borealis, or Northern Lights, across Canada and the northern U.S.

People in northern New England, the far northern Plains, and the Pacific Northwest should have the best views of the aurora. The best views should be Friday night, but some auroras could be visible Thursday night.

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.

Contributing: Trevor Hughes, Elizabeth Weise; and Associated Press