Severe Level 4 Magnetic Storm - March 17, 2015

The most powerful solar storm in years is rattling Earth's magnetic field today, bringing the potential to disrupt satellite communications and power grids on the ground. But with the luck of the Irish, the biggest effect might be only a great green show of northern lights.

On Sunday, two giant clouds of charged particles called coronal mass ejections, or CMEs, flew off the sun. Along their 93-million-mile journey to Earth, these solar tsunamis merged into one huge storm that slammed into Earth's bubble-like magnetic field at 12:30 a.m. EDT (0430 UT) this morning. The storm level has been intensifying ever since. Watch the aurora borealis live during the St. Patrick's Day solar storm.

The solar blast ranks as a G4, or severe, storm on the National Oceanic and Atmospheric Administration's cosmic Richter scale of geomagnetic storms, and it's the most intense to hit the Earth since the fall of 2013.

Solar storms can cause fluctuations in electric fields that have disrupted satellites and power supplies in the past. In March 1989, for instance, an intense geomagnetic storm shut down the entire Quebec power grid, leaving millions in the province without power for 12 hours.

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The planet's ionosphere receives the worst of a solar blast and becomes more dense during peak times of intense storms. That can put a significant drag on low-Earth-orbiting satellites that travel through the upper ionosphere. Astronauts aboard theInternational Space Station are not expected to be in any danger, however. And there has been no word yet if satellite operators have had to make any orbital corrections today.

While television signals should not be affected, the storm could be severe enough to disruptGlobal Positioning System reception, which could affect GPS and smartphone users. There may be fluctuations in accuracy, and systems may respond more slowly than usual.

Ham radio operators might see some disruptions in their signals as well, since they bounce their signals off the ionosphere to transmit them long distance.

The storm is expected to continue for another 24 to 48 hours. NASA andNOAA are monitoring the situation.

Skies May Glow Green Tonight

Geomagnetic storms often bring the northern lights to lower latitudes than auroras are usually seen. Before dawn this morning, sky-watchers from Alaska to Washington, Minnesota, Wisconsin, and the Dakotas reported seeing the northern lights.

With nightfall now under way in Europe, many more may witness the colorful effects of this storm in the coming hours. If the solar storm remains intense into the nighttime hours for North America, sky-watchers in Canada and northern and midlatitude U.S. states could soon see beautiful green auroras.

A severe geomagnetic storm, first observed at 09:58 a.m. EDT, should spark colorful auroras before waning toward the end of the day. This model depicts where the light shows should be visible.

 
PHOTOGRAPH COURTESY NOAA

The northern lights can be seen after nightfall tonight, but the best shows will most likely appear closer to local midnight, when skies are darkest.

Weather permitting, brighter and more intense aurora displays may also be visible across northern Europe and northerly parts of Canada.

Observers in more southerly regions of North America may also luck out if the storm intensity continues into tonight. People as far south as New Mexico and Oklahoma may see ghostly green glows close to the northern horizon.