The Discovery of Steve: An Aurora By Any Other Name
Estimated read time: 4-5 minutes
GREEN BELT, Md. — 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 over an informal chat.
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.
About eight years ago, when Elizabeth MacDonald, a space physicist at NASA’s Goddard Space Flight Center, was in Calgary, Canada, 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.
Naming the spectacle
At the time, “we didn’t exactly know what it was,” MacDonald said of the phenomenon featured in the images.
“I started spotting what we used to call a proton arc in 2015,” photographer Neil 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.”
Eric Donovan, a professor at the University of Calgary who was at a pub with MacDonald that day, assured Zeller he had not 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.
What is Steve?
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. 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.
Photographer Donna 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.
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.
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 Sept. 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.