The sky over an unusually wide swath of the northern hemisphere lit up with a brilliant display of color overnight into Monday morning, dazzling people across North America and Europe.
The display was potentially visible as far south as Iowa in the United States, as well as in parts of southern England, scientists said.
The phenomenon, known as the aurora borealis or northern lights, occurs when particles emitted by the sun collide with particles that are already trapped around Earth’s magnetic field, and can often be seen from parts of Iceland, Canada and Alaska.
But on Friday, the sun let off a large burst of energy, said Robert Steenburgh, a space scientist with the Space Weather Prediction Center at the National Oceanic and Atmospheric Administration. (These bursts are also known as coronal mass ejections.)
“The sun spit off a big blob of plasma,” Mr. Steenburgh said. The burst of energy, which has its own magnetic field, had been moving through space and reached Earth’s magnetic field on Sunday, when the two collided to create a geomagnetic storm, he said. “It got our magnetosphere pretty revved up.”
When this happens, the aurora can be seen closer to the Equator, Mr. Steenburgh said. Such events are not that uncommon, with about 100 occurring every 11 years, he said, adding that the storm can also disturb high frequency radio used at sea and by airlines.
Anyone who did not see the light show overnight might have missed their moment, as geomagnetic and storm activity is expected to ease on Monday, he said.
“There is still a chance we have some lingering effects, but definitely not of the magnitude you saw last night,” Mr. Steenburgh said.
Viewing of the phenomenon can also be less optimal as summer approaches, he added. “You’re going to have longer days, so nighttime opportunities will be fewer to catch these things,” he said.
For those unaccustomed to seeing the night sky illuminated by streaks of green or red, an aurora borealis — in folk tales, the northern lights have been associated with spirits and divine forces — can inspire awe, or even fear.
In 1872, an article in The New York Times described a sky glowing so intensely that “many persons supposed a great fire was raging back of Brooklyn.” In 1941, hundreds of onlookers gathered on the boardwalk of Rockaway Beach, N.Y., to view the phenomenon, and in 1929, many readers of The Times called the paper to report the dazzling sight.
On Sunday evening, forecasters in the United States said the geomagnetic storm was likely to cast an aurora that could be seen from some northern states like Maine and Michigan. Britain’s national weather service, the Met Office, predicted that people in Scotland and northern England would be able to see the lights, with another chance to view them on Monday night into Tuesday.
On Sunday, the storm created a spectacular show of light.
Forecasters with the National Weather Service office in Riverton, Wyo., shared images of a sky painted with deep purples and bright greens. The northern lights could also be seen over Maine and parts of Wisconsin, as well as in Toronto, in Canada.
In Europe, the northern lights were seen over southern England, where streaks of magenta and yellow illuminated the skies above Stonehenge.
Christine Hauser contributed reporting.
