The fabled northern lights may be making a rare local appearance this weekend, thanks to a massive eruption on the surface of the sun.
Solar scientists say New England residents have a better than 50 percent chance of glimpsing the northern lights, or aurorae, starting tonight, as particles ejected from the sun earlier this week hurtle towards 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 arrive 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 agree the lights could be visible in the northern sky as early as sunset today. They will likely reach their peak in the early morning hours of Sunday, and may continue into Sunday night. The lights could appear as far south as the mid-Atlantic states, though they will almost certainly be easier to see from central and northern New England, scientists said.
Viewing conditions will be mixed, according National Weather Service meteorologist Frank Nocera.
“Tonight we’re going to have some clouds on the southern horizon, and that may be an issue, Nocera said. “Tomorrow night, the sky should be pretty clear. We’ll have a better shot at good viewing conditions.’’
Scientists say that while the event is unlikely to cause serious power grid or travel disruptions, it could 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. 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 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.’’