WASHINGTON - A wave of charged plasma particles from a huge solar eruption has glanced off the Earth's northern pole, lighting up auroras and disrupting some radio communications, a Nasa scientist said.
But the Earth appears to have escaped a widespread geomagnetic storm, with the effects confined to the northern latitudes, possibly reaching down into Norway and Canada.
"There can be sporadic outages based on particular small-scale events," said Dean Persnell, project scientist at Nasa's Solar Dynamics Observatory at Goddard Space Flight Center.
He said the official forecast is "for generally quiet conditions today, perhaps some minor storming tomorrow, but nothing extraordinary."
The event began Tuesday (at 0156 GMT) with a spectacular solar eruption in a sunspot the size of Jupiter that produced a Class X flash - the most powerful of all solar events.
The eruption blasted a torrent of charged plasma particles called a coronal mass ejection (CME) toward Earth at about 900 kilometres per second, the Solar Dynamics Observatory reported.
A direct hit from a CME could trigger a huge geomagnetic storm as incoming particles bounce off the Earth's geomagnetic field, blacking out radio communications, interfering with GPS navigational systems, in theory even causing power outages.
The China Meteorological Administration reported that the solar flare caused "sudden ionospheric disturbances" in the atmosphere above China and jammed shortwave radio communications in the southern part of the country.
Anticipating the worst, the US National Weather Service's Space Weather Prediction Service warned it was "the calm before the storm."
"Three CMEs are enroute, all a part of the Radio Blackout events on February 13, 14, and 15 (UTC). The last of the three seems to be the fastest and may catch both of the forerunners about mid to late ... February 17."
But Persnell said the spiralling beam of solar particles from Tuesday's eruption was passing behind the Earth without making a direct hit.
"In this case, it appears it will curve around and not hit us," he said.
He said satellite data "shows that the CME is quieting down and so there is not a whole lot left to it. So it's moved well behind us by now," he said.
But he said solar activity is on the upswing, and more CMEs will follow.
"We are seeing more and more sunspots as what we call solar cycle 24 is turning on," he said. "At the peak we might see several of these CMEs a day coming off the sun."
"But they have only a five to ten per cent chance of hitting us. We have to be in exactly the right place for that piece of spiral to come hit us. We'll see many more coming off the sun than we have hitting us here on Earth."
The British Geological Survey (BGS) said, meanwhile, that the solar storm would result in spectacular Northern Lights displays starting on Thursday.
One CME reached Earth on February 14, "sparking Valentine's Day displays of the Northern Lights (aurora borealis) further south than usual."
The office published geomagnetic records dating back to the Victorian era which it hopes will help in planning for future storms.
"Life increasingly depends on technologies that didn't exist when the magnetic recordings began," said Alan Thomson, BGS head of geomagnetism.
"Studying the records will tell us what we have to plan and prepare for to make sure systems can resist solar storms," he said.
A 2009 report by a panel of scientists assembled by Nasa said that a sustained and powerful solar flare outbreak could overwhelm high-voltage transformers with electrical currents and short-circuit energy grids.
The report, titled Severe Space Weather Events - Understanding Societal and Economic Impacts warned that such a catastrophic event could cost the United States alone up to two trillion dollars in repairs in the first year - and it could take up to 10 years to fully recover.