It spans the sky like a mega-size wad of chewing gum stretched taut. It glows from within, pulses gently and sometimes releases tentacles of dripping, green ectoplasm.
It’s Steve, a mysterious space-weather emanation that’s expected to peak around the spring equinox on March 20.
As far as anybody knows, Steve has been doing its groovy dance in the heavens forever. But it wasn’t until a group of Canadian photographers called the Alberta Aurora Chasers brought it to light in 2016 that it began to receive formal recognition. As is typical with many advances in science, this happened at a bar.
The chasers were drinking with Eric Donovan, a professor of physics and astronomy at the University of Calgary, and Liz MacDonald, a space-weather scientist with NASA Goddard, when one of them whipped out a photo of a supposed proton arc.
“I said, ‘I don’t know what that is, but it’s not a proton anything,’ ” Donovan recalls. The group decided to call the thing “Steve,” a tribute to the children’s animation film “Over the Hedge,” in which a band of talking animals runs across a trimmed bush and, not knowing what it is, calls it “Steve.”
“I’d been watching that movie with my kids over the week prior, so it was in my mind,” says Chris Ratzlaff, a Calgary-area chaser who suggested the name.
He adds: “I’m the kind of person who as soon as someone says, ‘Hey, let’s name this planet,’ I’ll call it ‘Bob.’ Just, yeah — I can’t really explain it better than that.”
The name stuck, though researchers now know it by the more-official sounding STEVE, short for Strong Thermal Emission Velocity Enhancement. Those who run across one on a cold, lonesome night walk away with a lasting impression.
“Like watching the auroras dance, watching Steve pulse and move across the night sky is like magic and mesmerizing,” says Mitch Popilchak of the Alberta Aurora Chasers. He snared this shot of Steve in 2017 in Pincher Creek, Alberta:
Renaud Cheyrou, another Alberta chaser, encountered it the same year during a crackling G2 geomagnetic storm over the Canadian Rockies. “It was incredible,” he says. “I’ve heard about it and never seen it before that night, and I will remember this for a long time!”
Bagging a Steve can be a badge of honor for space-weather enthusiasts.
“I can’t speak for places outside of Alberta, but I suppose there’s a certain amount of bragging rights for capturing a powerful Steve display in a beautiful setting,” says Clark Monson, who witnessed Steve near Mount Robson, British Columbia:
“Steve was a very pale purple, but the camera picked up the color really well,” Monson says. The “picket fence” — the term for the green tendrils that sometimes, for unknown reasons, dangle off Steve — moved “slowly across the sky and pulsed quickly upward from bottom to top as they moved.”
The science on Steve is relatively new, but here’s what’s known: Steve tends to appear several hundred miles south (or north, in the Southern Hemisphere) of the typical aurora zone. It has been spotted in higher-latitude locations such as Canada, New York, Michigan, Montana, Scotland and Tasmania, and resembles a purplish airplane contrail flowing hundreds or thousands of miles across the celestial dome.
Steve can last for minutes or upward of an hour, and during that time manifests queer optics. “Light at essentially all wavelengths in the optical band is enhanced where Steve is,” Donovan says.
While Steve often accompanies auroras, it is not one. Some scientists believe Steve is the result of narrow, extremely fast-moving rivers of ions colliding with neutrally charged particles in the atmosphere.
“But can we give enough energy to the neutral particles to get them to give off light?” Donovan asks. “That’s a question I do not have an answer to; it’s the number-one question we have to explore now.”
Sightings of Steve surge in the weeks around the fall and spring equinoxes. That could be because more sky-watchers are active on these warmer, longer nights — not everybody has the grit required to survive high-north winters. But NASA’s MacDonald thinks Steve is “definitely” more prone to exposing its lavender belly during these periods, citing evidence she has collected from watchers on her citizen-science site, Aurorasaurus.
“But I do not think we know all of the complex reasons why this occurs,” she says. “Specifically, it’s not just the reasons why the aurora also has seasonal peaks.”
MacDonald believes time will reveal valuable secrets about Steve.
“It is extremely rare to connect a specific auroral feature to its drivers far away in space in the magnetosphere, and Steve presents unusual opportunities to do so,” she says. “In six more months, there will be quite a bit more new results on this, I believe.”
Those wishing to catch a Steve in the wild need nothing more than a good app for predicting aurora outbreaks and a camera (ideally with a tripod) capable of taking long exposures, as Steve can be quite faint. Look for a lilac emanation running from west to east that resembles a narrow beam or arc; some chasers say it often occurs several beats after the more-grandiose auroras subside.
Or, if you happen to be in the Canadian countryside, you can just follow murmurings in the darkened hills and froggy ponds favored by aurora hunters.
“If you’re in a group of [chasers], you’ll hear either a shout or someone will lean over and go, ‘Is that Steve?’ ” Ratzlaff says. “It’s kind of like catching a rare bird.”
John Metcalfe is a freelance writer based in California. He previously worked as a journalist for CityLab, covering climate change and the science of cities.