03/16/2018

A New Clue To The Pinkish Streak Named Steve

6:28 minutes

a timelapse of steve in the sky
An early evening appearance by Steve over Helena Lake Ranch, BC, Canada. Steve was visible for about an hour before disappearing into the night sky. Credit: Andy Witteman, @CNLastro

How do you solve a puzzle like Steve? That was the name given to a mysterious southerly pink streak in the aurora borealis, after aurora enthusiasts using the citizen science platform Aurorasaurus began to notice the streak appearing again and again in the images they were sharing.

Steve has transformed from a tongue-in-cheek reference to the 2006 movie Over the Hedge into an actual acronym: Strong Thermal Emission Velocity Enhancement. And, thanks to a fortuitous alignment of a citizen Steve sighting with a satellite flyover in 2016, new research published this week in Science Advances could point to what exactly Steve is—the visual component of a high-energy river of particles in the atmosphere.

[Find out how Stephen Hawking got sucked into black holes.]

Elizabeth MacDonald, study author, Aurorasaurus founder, and NASA plasma physicist, explains why Steve is different from standard aurora sightings, and discusses the continued role for citizen scientists in helping us understand Steve.


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Segment Guests

Liz MacDonald

Liz MacDonald is the founder of Aurorasaurus. She’s a space plasma physicist at NASA in Greenbelt, Maryland.

Segment Transcript

FLORA LICHTMAN: You might have met Steve. Steve is kind of a loner yet extremely popular and very weird. Steve does not come out in winter.

Steve is pinkish mauve and manifests as a streak in the sky. Steve is a phenomenon in the aurora– the Northern Lights that citizens, scientists, and aurora enthusiasts have been looking at for the past couple of years. And Steve has attracted a lot of attention because it just doesn’t look like the rest of the aurora, and it’s often much further south than typical aurora colors.

But new research– a collaboration between citizen observers and professional scientists– has an answer for what might be causing Steve. It’s published in the journal Science Advances This Week. I’ll let my next guest explain what they learned and explain why Steve is named Steve. Liz McDonald is founder of the citizen science project Aurorasaurus and a space physicist at NASA’s Goddard Space Flight Center. Welcome back, Liz.

LIZ MACDONALD: Hi, thank you.

FLORA LICHTMAN: Why is Steve named Steve?

LIZ MACDONALD: So first, for those of you who don’t know, the citizen scientists and amateur photographers were photographing the night sky. They saw this different thing. It used to be called a proton arc.

But in talking to the scientists from NASA and the University of Calgary, we didn’t think that was an appropriate name. So they said, OK, we’ll give it a new name and keep taking observations. And so the name is inspired by the movie Over the Hedge, and it was named by Chris Ratzlaff, who’s the administrator of the Alberta Aurora Chasers, a Facebook group.

FLORA LICHTMAN: So Steve was named by the people but sounds like you’re sticking with it.

LIZ MACDONALD: Yeah, so the paper shows a result where all the stars– actually, the Steve and the ESSA satellites swarm– aligned and really allowed us to understand more about the true meaning of Steve. And so what we found was that Steve is associated with a really strong flow of particles in the upper atmosphere. And that is associated with heating of the plasma and also that somehow causes the glow of Steve, which is different. And so we’re keeping the name.

When we see it from satellites, we do know what it is. It’s a subauroral ion drift. And that’s something that has been studied for a long time but never known to have this visible component. So that’s what’s new and really exciting.

And the name we’ve given it a backronym to be Strong, Thermal, Emission, Velocity, Enhancement, corresponding to what you see in the upper atmosphere. Corresponding to what’s causing Steve.

FLORA LICHTMAN: I’m Flora Lichtman, and this is Science Friday. From PRI Public Radio International. OK, so river of ions. What I’m trying to imagine what it is exactly. Can you just sort of break it down for me even further?

LIZ MACDONALD: Yeah, it’s a little hard to explain because the aurora is happening farther to the north, and then there’s a gap, and then there’s this narrow ribbon of light. And the aurora is driven by processes that happen hundreds of thousands of miles out in the near-Earth space environment– the magnetosphere. But at lower latitudes, Steve is corresponding to something happening still out in the magnetosphere but closer in in the inner magnetosphere. So that’s where the subauroral ion drift is getting set up. And it’s driven by the same phenomena that’s driving and enhancing the aurora.

FLORA LICHTMAN: But so is this just particles from the sun? When you say subauroral drift, are we talking about charged particles from the sun that are hitting particles in the magnetosphere?

LIZ MACDONALD: Yeah, so that’s what normally drives the Aurora. And those particles come in, and they bounce off the upper atmosphere and release light. And in this case, it’s actually a different mechanism in the upper atmosphere that we think is producing the light. It’s that the drift is so strong that the plasma– the charged particles– move, and they heat up the neutral particles in the very upper level of our atmosphere. And so that’s a different mechanism causing the light.

FLORA LICHTMAN: Why is Steve pinky-purple?

LIZ MACDONALD: That also we don’t fully know, and it is related to that drift. We think that at these latitudes, the chemistry of the upper atmosphere is getting changed by this strong drift. And so you have some really exotic wavelengths of light being excited that are different than the wavelengths that are excited in the normal aurora because of the different process.

FLORA LICHTMAN: It’s amazing to me that we didn’t know Steve existed until now.

LIZ MACDONALD: Yeah, this region is not very well studied. And so there are still some mysteries out there. And so it’s really exciting that citizen scientists, with their photographs, have captured these new aspects. So mostly Steve is purple, but you also get a little bit of green light that pops up and moves around. And that is some really exotic plasma physics that we don’t even understand yet.

FLORA LICHTMAN: Where can I see Steve?

LIZ MACDONALD: So you can see Steve. It’s been reported all over Alberta and most of Canada, also Scotland, Tasmania. I just found out today New Zealand and slightly less exotic places like Michigan and Montana.

FLORA LICHTMAN: Are there other Steves out there?

LIZ MACDONALD: There could be some more mysteries in the night sky. Our citizen science project is happy to collect observations from people and work with people for deeper understanding of what they may be. And really by working together– it’s not just one observation. It’s several observations of Steve. And so we can better characterize these new characteristics.

FLORA LICHTMAN: And where should people go if they want to get involved with Aurorasaurus?

LIZ MACDONALD: It’s Aurora Saurus, like a dinosaur, dot org.

FLORA LICHTMAN: That’s great. Thank you so much. Liz MacDonald, founder of Aurorasaurus and a space physicist at NASA’s Goddard Space Flight Center. Thanks for coming on the show.

LIZ MACDONALD: Thank you.

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