Northern Lights Could Be Visible In U.S. On Christmas: When, Where To Watch

ACROSS AMERICA — A solar storm could bring a northern lights display to some parts of the upper U.S. on Thursday, according to the Space Weather Prediction Center, which issued a geomagnetic storm watch.

The solar flare heading toward Earth is called a coronal mass ejection, or CME — a huge expulsion of plasma from the sun’s outer layer, called the corona.

Where aurora borealis displays can be seen is difficult to predict, but a map on the Geophysical Institute at the University of Alaska-Fairbanks website shows the northern lights could be visible from Great Falls, Montana, to upper Maine.

Forecasters from the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center said the faint solar storm cloud left the sun Monday, propelled by an M1.9-class solar flare.

Experts expect a “glancing blow to Earth’s magnetic field … possibly sparking a G1-class geomagnetic storm,” then added:

“Christmas Lights, anyone?”

Solar storms that approach Earth are graded by severity. A G1 storm is relatively minor, but it could cause some minor instability to power grids and satellite communications.

The science behind the jaw-droppingly beautiful aurora borealis is a bit complicated. Basically, the northern lights become visible to the human eyes when electrons from solar storms collide with the upper reaches of the Earth’s atmosphere.

In normal circumstances, the Earth’s magnetic field guides the electrons in such a way that the aurora forms two ovals approximately centered at the magnetic poles. But during geomagnetic storms, the ovals expand away from the poles and give some lucky people in the United States a sky show they’ll never forget.

Most often, the auroras appear as tall rays that look like a colorful curtain made of folds of cloth, according to the Space Weather Prediction Center.

“During the evening, these rays form arcs that stretch from horizon to horizon,” the agency said on a website. “Late in the evening, near midnight, the arcs often begin to twist and sway, just as if a wind were blowing on the curtains of light. At some point, the arcs may expand to fill the whole sky, moving rapidly and becoming very bright. This is the peak of what is called an auroral substorm.”