Satellite operators and power companies are keeping a close eye on the incoming cloud, which could distort the Earth's magnetic field and disrupt radio
communications, especially at higher latitudes.
"Our simulations show potential to pack a good punch to Earth's near-space environment," said Antti Pulkkinen of the Space Weather Laboratory at Nasa's Goddard Space Flight Center in suburban Greenbelt, Md But "we're not looking at an extreme event here."
The front edge of the burst should arrive Sunday morning, said Joseph Kunches, a spokesman for the Space Weather Prediction Center, part of the National Oceanic and Atmospheric Administration in Boulder, Colo.
"At first glance, it was, 'Oh my God, it's at the center of the (sun's) disk, it ought to go right to the Earth,'" Kunches said.
But upon further review and "head-scratching" Thursday, NOAA's space weather team calculated that most of the plasma blob should pass harmlessly over the top of our planet.
"It's more of a glancing blow," Pulkkinen said.
At their most intense, solar discharges, known as "coronal mass ejections," can disrupt satellites, radio communications and the power grid, and force airlines to reroute transcontinental flights that pass near the North Pole. Solar activity can also generate dancing auroras, the northern and southern lights.
Spit out by the sun Thursday morning, the huge blob of charged gas spotted by Nasa satellites is speeding toward Earth at more than 2 million mph.
The most damaging solar discharges, which are very rare, can zoom at speeds more than twice that fast.
The ejection appears to be the most threatening since the sun spit out three large blobs in quick succession last August. Such discharges shoot out of sunspots, which are dark areas on the sun's surface where tangled magnetic fields sometimes discharge massive spurts of energy.
Solar activity ramps up and down on a roughly 11-year cycle. Over the past year, the number of solar flares has jumped
up as the sun approaches its predicted maximum activity in 2013.
While the Earth appears to have dodged this particular solar bullet, the roiling sunspot could generate more activity over the coming week before it rotates out of the view of the Earth.
"We are keeping a close eye on the event," Pulkkinen said.
Besides sparking pretty auroras, heightened solar activity has a more tangible benefit: It cleans up space junk.
As the sun acts up, the Earth's atmosphere expands, increasing friction on dead satellites, rocket parts and other trash in low Earth orbit, pulling them down.
The amount of debris in Earth orbit "actually decreased during 2011 as solar activity increased toward an anticipated maximum," Nasa's chief space junk watcher, Nicholas Johnson, wrote in the January issue of the agency's Orbital Debris Quarterly Newsletter.