Citizen scientists help reveal new features of the mysterious aurora-like phenomenon called STEVE

Originally published on December 12, 2020.

Neil Zeller had no idea when he first photographed the unusual aurora-like phenomenon now known as STEVE half a decade ago, that one day he'd become a co-author on a scientific paper about it.

"We look at them, we just say, 'wow, this is incredible,'" said Zeller. "And then when science looks at it, they say, 'wow, what is that?'"

To the naked eye STEVE, which accompanies the regular aurora borealis, or Northern Lights, can be mistaken for an aircraft contrail in the sky. But when captured by a much more sensitive camera, it's revealed to be a distinct phenomenon — a thin mauve arc of light across the sky that's "almost flowing like a river," according to Zeller.

Zeller and his fellow aurora-chasers are, in fact, the reason that this phenomenon is known to the scientific world. More recently Zeller and other aurora-chasers have contributed to research about STEVE's "green picket fence" features that often accompany mauve streak overhead.

"We call them picket fences because they're parallel to each other, but they're kind of flowing and motioning in the sky," Zeller told Quirks & Quarks producer Sonya Buyting.

STEVE's name was originally from one of the aurora chasers, who was inspired by the children's movie, Over the Hedge, in which hibernating animals woke up to find a hedge they'd never seen before, and decided to name it "Steve" to make it less scary. 

Fast hot flow of ions

"Steve" only came to the attention of researchers in January of 2016, when members of the Alberta Aurora Chasers' Facebook group met with aurora scientists at a pub one night, after a public talk at the University of Calgary. 

Zeller was sitting with Eric Donovan from the University of Calgary and Elizabeth MacDonald from NASA. MacDonald had given a lecture about the Northern Lights and her citizen science project called Aurorosaurus.

Zeller told them about a photo he'd taken of the phenomenon that would later become known as STEVE, which other photographers had incorrectly identified it as a proton arc, which Donovan took to mean proton aurora.

Donovan told him that he didn't know what the mauve streak was, but he knew it wasn't a proton aurora because it would not have been visible to the naked eye. Proton auroras are similar to typical electron-driven aurora borealis, except they're driven by positively charged protons crashing into Earth's atmosphere.

As it turned out "Steve" was, in fact, unknown to science. Donovan immediately decided to investigate. 

Donovan operates the world's most extensive network of ground-based instruments, situated from coast to coast, for taking optical measurements of the aurora. So he suspected he had the scientific images in which he could look for signs of what he suspected the phenomenon might look like in his data.

"We could then use that information, together with observations by satellites that measure in situ what's going on with electric currents and precipitating particles and so on. And we could use all of that mechanism to explore what STEVE is," said Donovan.

A few months later, they caught their break in Lucky Lake, Saskatchewan. 

One of the instruments in his network picked up a signature he thought could be "Steve." 

Donovan went onto Facebook, to the Alberta Aurora Chasers group, to ask if anyone had observed or taken images of "Steve" the night before. 

I'm in it for the beauty of it, but to be cited and being a part of these studies is just fantastic.- Neil Zeller, Aurora chaser and professional photographer

Within minutes, a woman in Alberta sent him a couple of high resolution photos. And then within an hour of getting those photos, a colleague told him one of the SWARM satellites that takes measurements of the aurora passed directly by "Steve."

"We could see very clearly that "Steve" was a very, very fast westward moving jet of ions going like seven kilometres per second, so super fast. And the temperature in that region was super high," described Donovan.

With these new scientific findings, "Steve" was re-designated STEVE by researchers, as a "backcronym" for Sudden Thermal Emission Velocity Enhancement.

Mapping out features in the green picket fence

Five years after that first meeting spawned investigation of STEVE, the latest research, which attempts to explain the green picket fence phenomenon associated with STEVE, has now been published in the journal AGU Advances.

NASA's Elizabeth MacDonald was one of the scientists who contributed, along with several citizen scientist aurora chasers, like Zeller. 

The study looked particularly at tiny green streaks at the bottom of the picket fence which, MacDonald said, could be moving points of light. She said citizen scientists were major contributors to the research.

Michael Hunnekuhl, an aurora enthusiast from Germany, did a lot of the analysis to map out the tiny green streaks using photos from other aurora chasers like Zeller, she said.

"He was able to look at where those photographs were taken and the exact geometry of the people from their different viewpoints on the ground, and the timing, and work all of that out in order to calculate the altitude of those tiny little streaks," said MacDonald.

She said it appears as though the green picket fences and the tiny little green streaks at the bottom of them are caused by turbulence at the edge of the flow of hot ions that creates the mauve streak that is STEVE's primary feature.

"We understand a lot of the properties that could be causing that, but to put it all together and actually model what we now see, is the next challenge."

But for citizen scientists like Zeller, he said he's just glad he was there that day. 

"I'm in it for the beauty of it, but to be cited and being a part of these studies is just fantastic," he said.

Produced and written by Sonya Buyting.