Scientists identify mysterious light phenomenon in the sky – and name it Steve

Academic paper suggests fluorescent phenomenon to be known as Strong Thermal Emission Velocity Enhancement

The spectacle consists of a strip of ionised gas which is as hot as the Earth's core (National Geographic/Notanee Bourassa)

For years, skygazers in Canada have been training their camera lenses on a wispy strand of purple light running across the country from east to west, sometimes flanked by neon green fingers that appear to wave.

It looks like a piece of the aurora borealis, or northern lights: blushes of pink or green that illuminate the night sky at high latitudes, caused by solar particles interacting with the Earth’s magnetic field.

But this strip of light is different. It has always appeared further south, beyond the bounds of normal aurora sightings.

Amateur aurora watchers have taken hundreds of photographs of this adjacent phenomenon, often drawing out its fluorescent colours with long exposures or photo editing. They called it Steve, as a sort of placeholder until a more formal name could be found.

Now a research paper has shed light on what Steve actually is and scientists have proposed a moniker: Strong Thermal Emission Velocity Enhancement.

So, it’s still Steve. But as a bacronym – a retroactive acronym.

The paper was published Wednesday in Science Advances, a peer-reviewed journal from the American Association for the Advancement of Science. It suggests that Steve has a lot in common with a phenomenon called a “sub-auroral ion drift” or SAID, in which ions flow very quickly from east to west, closer to the equator than the aurora borealis.

Like the northern lights, SAID results from interactions between charged solar particles and the Earth’s magnetosphere.

“It’s something that we know that’s actually been studied for 40 years,” said Elizabeth A MacDonald, a space physicist at Nasa’s Goddard Space Flight Center who led the paper’s research team. “But they have never been seen to have this optical component.”

In other words, SAID usually looks nothing like Steve, with its long purplish streak and green fingers. That leaves many questions unanswered and scientists are still working on those.

In 2014, Ms MacDonald founded a platform called Aurorasaurus to share images of the northern lights and, more recently, Steve. She works with contributors who are not formally trained scientists, like Hannahbella Nel, a British photographer who travelled to Canada and captured a stunning display of Steve in May.

“Last month, Aurorasurus put out a call for photographs of Steve for a research paper. I was happy to submit mine,” Ms Nel said in an email on Wednesday. “I found it exciting, as I wanted to know more about this beautiful ribbon of light I had captured with my photographs.”

Ms Nel is also a member of a Facebook group called the Alberta Aurora Chasers. For years, its members have gathered on Canadian prairies, far from the city lights, to catch glimpses of the aurora.

On those trips, they began to notice Steve and Chris Ratzlaff, the group’s administrator, gave the strip of light its name. He was inspired by a scene from the 2006 animated movie Over the Hedge, in which a group of animals encounter a tall hedge and not knowing what it is, decide to call it “Steve”.

When Ms MacDonald visited the University of Calgary to give a talk in 2016, Mr Ratzlaff and other members of his Facebook group attended. She met them at a pub, along with Eric Donovan, a professor of physics and astronomy at the university. As they pored over photographs of Steve, collaboration began to take shape.

Ms MacDonald and Mr Donovan worked with data from Swarm, a constellation of satellites run by the European Space Agency and learned that Steve is a strip of ionised gas as hot as the Earth’s core and moving through the air at about 4 miles per second.

Further research revealed that Steve was similar to a sub-auroral ion drift – something Mr Ratzlaff, who was named as a co-author on the Wednesday report, said he was not familiar with until this project began.

“SAIDs don’t really have any visual features, so the relationship between them and something as visually stunning as Steve is super fascinating,” he said, adding that his group will keep working with Ms MacDonald, Mr Donovan and others to understand the relationship between the two phenomena.

That collaboration between formally trained scientists and dedicated enthusiasts is what makes this project unique, Ms MacDonald said. “I think of it as a disruptive innovation,” she added. “Something unexpected that changes the way you look at things.”

The New York Times