This story was updated at 1:28 p.m. EST.
A wave of charged particles from an intense solar storm is pummeling the Earth right now, which may trigger stunning aurora displays and cause minor disruptions to satellites over the next two days, NASA scientists say.
The storm began when a powerful solar flare erupted on the sun yesterday (Jan. 23), blasting a stream of charged particles toward Earth. This electromagnetic burst, called a coronal mass ejection (CME), hit Earth at about 9:31 a.m. EST (1430 GMT), according to scientists at the Space Weather Center at NASA's Goddard Space Flight Center in Greenbelt, Md.
"It's a minor to moderate storm," Yihua Zheng, a lead researcher at the Space Weather Center, told SPACE.com. "Probably in the next 10 hours or so, people at high latitudes can see auroras. This could maybe cause communication errors at the polar caps, but the magnetic activities are probably not too strong."
The northern lights displays will be especially visible for people in northern latitudes where it is currently night.
"For parts of Europe already, and further points to the east, we should expect to see strong magnetic storm conditions," Harlan Spence, an astrophysicist at the University of New Hampshire, director of its Institute for the Study of Earth, Oceans, and Space, told SPACE.com. "There's a very good chance tonight that we'll be seeing some very strong auroral displays. Typically auroras occur at relatively high latitudes, but for events like this, you could get auroras down at mid to low latitudes."
When a coronal mass ejection hits Earth, it can trigger potentially harmful geomagnetic storms as the charged particles and the fields within it interact with the planet's magnetic field lines. This can amp up normal displays of Earth's auroras (also known as the northern and southern lights), but a strong CME aimed directly at Earth can also cause disruptions to satellites in orbit, as well as power grids and communications infrastructures on the ground.
Yesterday's solar flare set off an extremely fast-moving CME, Zheng said, and the associated radiation storm was the strongest since 2005. But the ejected cloud of plasma and charged particles was not directly aimed at Earth, and is hitting the planet at an angle instead. This glancing blow will likely lessen any impacts on Earth, she added. [Photos: Huge Solar Flare Sparks Major Radiation Storm]
"Earth's magnetic field served as a shield, and pretty much shielded the radiation so that it doesn't penetrate that deep," Zheng said. "It's like a car collision: head-on or off to the side. A CME is like that too. For this one, if it was a direct hit, Earth would receive a much stronger impact. This one was on an angle — toward higher latitudes and a little off the ecliptic — otherwise it would be a much stronger impact."
Still, the storm does rank as the biggest space radiation event in about seven years, Spence said.
"It's not as big as some of the big, historic storms, but the chance for re-intensification is still possible because this active spot on the sun that created the initial havoc could go off again," he explained.
Several NASA satellites, including the Solar Dynamics Observatory, the Solar Heliospheric Observatory (SOHO), and the Stereo spacecraft observed the massive sun storm. Data from these spacecraft were combined to help scientists create models to calculate when and where the CME was going to hit Earth.
"A CME is kind of like a space hurricane," Zheng said. "You have to predict how it will form and evolve. From the models, we can see which spacecraft will be in its path, and what will be impacted."
At the Space Weather Center, scientists were able to pinpoint the arrival of the CME more accurately than ever before.
"We predicted it would arrive at 9:18 a.m. and in reality, it arrived at 9:31 a.m., so ours has a 13-minute error," Zheng said. "Usually for this kind of model, the average error is seven hours, so this is the best case."
Yesterday's solar flare was rated an M9-class eruption, which placed it teetering on the edge of being an X-class flare, the most powerful type of solar storm. M-class sun storms are powerful but mid-range, while C-class flares are weaker.
The flare erupted from sunspot 1402, a region near the meridian of the sun that has been active for a while now, Zheng said. The powerful solar storm could be signaling that the sun is waking up after an extended period of relative dormancy.
The sun's activity waxes and wanes on an 11-year cycle. The star is currently in the midst of Solar Cycle 24, and activity is expected to continue ramping up toward the solar maximum in 2013.
Editor's note: If you snap an amazing photo of the auroras sparked by the solar storm, or other skywatching image, and would like to share it for a possible story or gallery, please contact managing editor Tariq Malik at firstname.lastname@example.org.