The fabled northern lights were expected to make an appearance in New England this weekend, thanks to a massive eruption on the surface of the sun.
Solar scientists say residents had a better than 50 percent chance of glimpsing the northern lights, or aurora borealis, beginning Saturday night, as particles ejected from the sun earlier this week hurtle toward Earth at more than 2 million miles per hour.
The northern lights are produced when charged particles from the sun interact with atoms in Earth’s upper atmosphere. The awe-inspiring displays — shimmering, translucent green, purple, and red “curtains” that seem to billow across the night sky — are common in extreme northern latitudes, where a constant stream of such particles arrives on the so-called “solar wind.” But in New England, and particularly in densely populated areas, sightings are unusual, generally spotted only when eruptions on the sun push the particles farther south and produce a geomagnetic storm.
“The sun constantly has particles streaming away from it — the solar wind — and that can cause aurora quite frequently in the north,” said C. Alex Young, the associate director for science at NASA’s Heliophysics Science Division. “These coronal mass ejections are like a wave riding on top of the wind. They strengthen the aurorae and can cause a geomagnetic storm.”
While computer-model predictions are imprecise and can differ by as many as seven hours, Young and other scientists said the lights were expected to reach their peak Saturday night. However, depending on the intensity of the storm, the lights could continue into Sunday night and be visible on the northern horizon. The lights were expected to be most easily visible from central and northern New England, scientists said.
Viewing conditions Saturday night were expected to be partially cloudy, according to National Weather Service meteorologist Frank Nocera. But on Sunday night, he said, “the sky should be pretty clear. We’ll have a better shot at good viewing conditions.”
Scientists say that while the event was unlikely to cause serious power grid or travel disruptions, it could temporarily throw off the accuracy of some GPS devices or cause other minor electrical failures.
Forecasters at the National Oceanic and Atmospheric Administration first noticed the coronal mass ejection Thursday night; particles in such ejections can take as few as 17 hours or as many as 100 to traverse the vast distance between the sun and Earth, depending on their speed. NOAA uses a fleet of satellites to constantly measure the sun’s activity from different angles and on different spectrums.
“As soon as the flare goes off, it triggers alarms. We have bells, whistles, and even a voice saying, ‘solar X-ray flare in process,’ ” said Bill Murtagh, the program coordinator at NOAA’s Space Weather Prediction Center, describing the scene at the group’s Colorado headquarters. “It’s always an exciting day. It’s like a nor’easter for us.”
An unusual lull in the sun’s activity over the past several years has scientists particularly excited about this weekend’s event, Murtagh said. The sun, which goes through a cycle of activity approximately 11 years long, should currently be in its most active state, the solar maximum. But a dearth of activity lately means this could be the least active solar maximum in more than 100 years, Murtagh said.
“I’ve been in the business for 20 years, but we have a lot of new forecasters who haven’t seen much activity since they started,” Murtagh said. For them, he said, it’s like seeing snow for the first time.
This particular ejection was not particularly huge, ranking just a G1 on NOAA’s scale, which goes from G1 to G5. However, the particles are aimed squarely at Earth, Murtagh said.
The strength of the aurorae partially depends on how fast the “blob” of plasma and charged particles is traveling when it impacts Earth’s atmosphere, scientists said. But a more important factor is the magnetic orientation of the blob: A south-oriented ejection will cause stronger interactions and more aurorae when it hits Earth’s north-oriented magnetic field.
“We know it’s coming, we know it’s good size, and we can tell how fast and big it is,” Young said. “But we won’t know about the magnetic field until about 30 minutes before it gets to us.”
The aurorae have long fascinated cultures around the world, which often interpreted their appearance as an omen of war or famine, Murtagh said. But modern Americans usually miss the show, since they live too far south, sleep through the infrequent geomagnetic storms, or are unable to see them because of light pollution or cloud cover.
“They’re inspiring to witness,” Murtagh said. “They’ve always had a mythical place in human history.”
Murtagh, who is Irish, has assigned his own mythology to this storm.
“The prevalent color of aurorae is green,” he said, “so maybe we’ll get some nice green aurora to kick off St. Patrick’s Day.”