These magnificent purple and green lights aren’t auroras – they’re Steve
(CNN) — Not all science is carried out by folks in white lab coats under the fluorescent lights of academic buildings. Occasionally, the trajectory of the scientific record is forever altered inside a pub over a pint of beer.
Such is the case for the sweeping purple and green lights that can hover over the horizon in the Northern Hemisphere. The phenomenon looks like an aurora but is in fact something entirely different.
It’s called Steve.
The rare light spectacle has caused a bit of buzz this year as the sun is entering its most active period, ramping up the number of dazzling natural phenomena that appear in the night sky — and leading to new reports of people spotting Steve in areas it does not typically appear, such as parts of the United Kingdom.
But about eight years ago, when Elizabeth MacDonald, a space physicist at NASA’s Goddard Space Flight Center, was in Calgary, Alberta, for a seminar, she had never seen the phenomenon in person. And it did not yet have a name.
In fact, few scientists actively studying auroras and other night-sky phenomenon had witnessed a Steve, which appears closer to the equator than auroras and is characterized by a purple-pink arch accompanied by green, vertical stripes.
After MacDonald gave a talk at a nearby university, she met up with some citizen scientists — mostly photographers who spend nights hoping to capture the next stunning image of colors dancing in the Canadian sky — at Kilkenny Irish Pub.
“I had already been reaching out to the local Alberta aurora chasers (in) a Facebook group, which was pretty small at the time,” MacDonald said, “but very keen to share their observations and to interact with NASA.”
The photographers came with their photos in hand, anxious to show the mysterious light show they had captured.
Naming the spectacle
At the time, “we didn’t exactly know what it was,” MacDonald said of the phenomenon featured in the images.
Neil Zeller, a citizen scientist or photography subject matter expert — as the aurora-chasing photographers are sometimes called — was at that meeting.
“I started spotting what we used to call a proton arc in 2015,” Zeller said. “It had been photographed in the past, but misidentified, and so when I attended that meeting at the Kilkenny Pub … we’d started a bit of an argument about (whether) I’d seen a proton arc.”
Dr. Eric Donovan, a professor at the University of Calgary who was at the pub with MacDonald that day, assured Zeller he had not have seen a proton arc, which according to a paper Donovan later coauthored is “subvisual, broad, and diffuse,” while a Steve is “visually bright, narrow, and structured.”
“And the conclusion of that evening was, well, we don’t know what this is,” Zeller said. “But can we stop calling it a proton arc?”
It was shortly after that pub meeting that another aurora chaser, Chris Ratzlaff, suggested a name for the mysterious lights on the group’s Facebook page.
Members of the group were working to understand the phenomenon better, but “I propose we call it Steve until then,” Ratzlaff wrote in a February 2016 Facebook post.
The name was borrowed from “Over the Hedge,” the 2006 DreamWorks animated film in which a group of animals are frightened by a towering leafy bush and decide to refer to it as Steve. (“I’m a lot less scared of Steve,” a porcupine declares.)
The name stuck. Even after the phenomenon could be better explained. Even after explanations for Steve began to take shape in scientific papers.
Scientists later developed an acronym to go with the name: Strong Thermal Emission Velocity Enhancement.
And that meeting in a small Canadian pub was a turning point.
“That was the in-person meeting that was one of the pieces that gave it more momentum to eventually collect more and more observations in a more and more rigorous way to where we could correlate that with our satellite,” MacDonald said.
What is Steve?
Eventually, MacDonald said a satellite directly observed a Steve, collecting crucial data and leading to a 2018 study that suggested the lights are a visual manifestation of something called subauroral ion drift, or SAID.
SAID refers to a narrow flow of charged particles in Earth’s upper atmosphere. Researchers already knew that SAID existed, MacDonald said, but they did not know that it might occasionally be visible.
Steve is visually different from auroras, which are caused by electrically charged particles that glow when they interact with the atmosphere and appear as dancing ribbons of green, blue or red. Steve — if it is caused by SAID — is made up of mostly the same stuff. But it shows up at lower latitudes and appears as a streak of mauve-colored light accompanied by distinctive green bands, often referred to as a picket fence.
Steve can be frustratingly difficult to spot, appearing alongside auroras with little regularity. Sometimes, spotting Steve is a matter of luck, noted Donna Lach, a photographer based in Canada’s Manitoba province.
Lach has seen and photographed Steve roughly two dozen times, a rare achievement in the world of sky photography. She said she uses her family farm on a remote plot of land in southern Manitoba, where there’s little to no light pollution.
She always checks the space weather before heading out. She’s looking for conditions to be at least a Kp3 — an index of space weather that ranges from Kp0 to Kp9, with higher numbers indicating more activity.
It appears, Lach said, that the phenomenon starts with the SAR Arc — a stable auroral red arc — that shows up near the auroral oval.
“It can eventually migrate south … toward the equator side of aurora and form a Steve,” Lach said.
A Steve will always appear alongside an aurora, Lach and Zeller said, but not all auroras include a Steve.
Where and how to see Steve
Earth is entering a period of enhanced solar activity, or solar maximum, which occurs every 11 years or so, MacDonald said.
During this time, spectators can expect more visible light shows in the sky and — potentially — the chance to witness a Steve at low latitudes. Light phenomena have been spotted as far south as Wyoming and Utah, she said.
“There have been recent storms that have been visible in the US — just a little bit — down to even, like, Death Valley,” MacDonald said. “And recently, the one in November … was visible at its southernmost point over Turkey and Greece and Slovakia, and even in China, which is very rare.”
Steve is best seen through the lens of a camera, however.
To the naked eye, it can appear as nothing more than what looks like a faint contrail from an airplane streaking across the sky, Zeller and Lach noted, and can be easy to overlook.
Cameras are much more sensitive to light, picking up Steve’s vibrant colors through their lenses.
Even a phone camera can work, MacDonald added.
“This is the first solar maximum, I would say, that most people’s cell phones can take a good picture of aurora,” she said.
The Steve phenomenon is most likely to be captured around the equinoxes in the spring and fall, according to Zeller and Lach. (This year’s fall equinox occurred on September 23.)
“I don’t think it’s Steve that occurs more during the equinox, but larger storms of aurora are well-known to occur more near the equinoxes,” MacDonald noted. And because Steve tends to appear alongside aurora, the phenomenon could be more likely to be observed in March or September.
Zeller and Lach said they typically see Steve between evening and midnight.
“It’s not an all-night thing,” Zeller said. “The longest duration Steve I’ve seen has been an hour from start to finish.”
Zeller added that he waits for an auroral storm to start to diminish before turning his camera eastward — from his vantage point in Canada — or straight up, then “you start seeing this purple river.”
That’s Steve.
How to become a citizen scientist
MacDonald encourages anyone who is interested in photographing auroras — or a Steve — to get involved with online communities. Aurorasaurus, a website that connects photographers with scientists, is a project she said she cares deeply about, noting its crucial role in helping scientists to formally identify Steve.
The photos contributed by members of the public constantly help scientists improve their understanding of these light shows, she said.
“Scientists are not as good of aurora chasers as the passionate public,” she said. “We don’t stay up all night, nor are we photographers.”