A series of eruptions on the sun delivered a rare and colorful display of the northern lights to Marylanders and sky watchers across much of the United States late Sunday. Those who missed the first show might be able to catch an encore this week.
Norm Lewis, WMAR-TV's weatherman, got a good look at Sunday's display of the aurora borealis from his backyard observatory in Mt. Airy.
"I've seen it before out here, but last night was unbelievable," he said. "Most of it was green, with some red mixed in. It started out ... looking like a long cloud. Then it started developing these vertical spires, so it came down in sheets and got very pronounced."
Similar descriptions and photos surfaced from California to Virginia, and as far south as North Carolina and El Paso, Texas.
Kurt Roelle, a member of the Westminster Astronomical Society, was sorting trash and recyclables at his New Windsor home about 7:30 p.m. Sunday when he noticed the aurora, low in the northern sky.
"What was real prominent was some of these green spikes, and it was changing very rapidly," he said. "They would form, get brighter, broaden and lengthen and then disappear."
The events were triggered by the first of a series of six powerful solar eruptions that began Wednesday and continued into the weekend.
With the last of those blasts still en route, "there's a good chance of seeing auroras again ... for the next two or three nights," said Larry Combs, a space weather forecaster at the federal government's Space Environment Center, in Boulder, Colo.
The weather should cooperate. The forecast calls for cold, clear skies through tomorrow night.
The solar flares, along with blasts of matter called coronal mass ejections, emerged from an active solar region near a large cluster of sunspots labeled 696. Each one hurled magnetic energy and billions of tons of electrically charged atomic particles toward the Earth at millions of miles per hour.
As such blast fronts reach the Earth, they rattle the planet's magnetic field. That causes geomagnetic storms that can trigger electrical surges in long-distance transmission lines, as well as disruptions of high-frequency radio and navigation systems. High-speed solar particles also can trigger glitches and failures in communications satellites in high Earth orbits.
In addition, geomagnetic storms send atomic particles smashing into the upper reaches of the atmosphere around the north and south magnetic poles. The impacts excite nitrogen atoms in the air, which glow red as they simmer down. Oxygen atoms closer to the surface glow green, and the combinations of colors sometimes add to the aurora's night palette.
Auroral displays are common in far northern latitudes. But unusually strong solar storms do push them farther south.
Alerted to Sunday's aurora by a telephone call, David Dunham, a spacecraft orbit designer at the Johns Hopkins University Applied Physics Lab, stepped onto his deck in Greenbelt about 10:30 p.m.
"I saw a green glow extending about 20 degrees high in the north," he said. "When I looked carefully I could see there was a rayed structure to it, and it was changing."
As Dunham watched, the display became larger and stronger, some of it rising well over halfway up the sky before fading away after midnight. "This was the first one I've ever seen from home," he said.
The last time Marylanders got a good look at the northern lights was on Oct. 29 and 30 last year, when the evening skies turned red and pink in the wake of some of the largest solar eruptions ever recorded.
Last week's flares and coronal mass ejections were smaller than that, Combs said. But their effects upon the Earth's magnetic field were relatively strong.
"It's hitting severe to extreme levels in the geomagnetic storm area," he said. "We have had some reports of minor induced currents within the [electric] power systems" in northern states. There were no immediate reports of damage to satellites, but "the airlines have been interested in this," he added.
Geomagnetic events can disrupt airliners' high-frequency communications. And higher radiation levels at far northern latitudes during solar storms can prompt airlines to alter their routes to protect passengers and crews.
For a photo gallery of Sunday's aurora, go to www.spaceweather.com