Scientists stumped by 'STEVE', a mysterious ribbon of light in the sky

The first serious scientific study of STEVE, the ribbons of white and purple light in northern skies, reveals they’re not auroras—they’re something new and unexplained.

Those of us who follow science news had a good chuckle when news broke a while back about a mysterious sky phenomenon appearing in auroral and sub-auroral regions dubbed 'Steve'. Well, Steve is actually STEVE, standing for Strong Thermal Emission Velocity Enhancement, and it’s no joke. What it is, on the other hand, is unknown.


Appearing in the dark sky as a mostly vertical ribbon of vibrant whites and purples with shimmering offshoots of green, STEVE has been photographed and video-recorded for decades. The scientific community, prompted by the citizen scientists who’ve been capturing images of it, is just now catching up.


(NASA/Goddard)

The initial assumption was that STEVE was some flavor of aurora borealis, but a new study published in Geophysical Research Letters—the first serious examination of STEVE—finds that it’s not. Bea Gallardo-Lacourt, lead scientist of the new study, says, “Our main conclusion is that STEVE is not an aurora. So right now, we know very little about it. And that’s the cool thing, because this has been known by photographers for decades. But for the scientists, it’s completely unknown.” She and her colleagues refer to the phenomenon as a 'sky glow'.


May 17, 2016. (Photo: Rocky Raybell)

Why it’s not an aurora

Auroras are caused by energetic particle precipitation, which is, as the name implies, a raining-down of high-energy electrons, protons, neutrons, and ions shot toward the earth from the sun. Earth’s magnetic field draws these particles towards our north and south poles.

When these highly charged particles hit Earth’s atmosphere, they collide with atoms and molecules of oxygen, nitrogen, and other elements to produce both the aurora borealis (North Pole) and aurora australis (South Pole). When particles interact with oxygen, yellow and blue light is produced. Nitrogen encounters result in red, violet, and sometimes blue lights, depending on the type of collision that occurs. According to NASA, atomic nitrogen causes blue lights while molecular nitrogen tips beams to purple.

The standout finding of the new research is that STEVE displays don’t involve particle precipitation, meaning, as the study says, that “its skyglow could be generated by a new and fundamentally different mechanism in the ionosphere.”

How we know STEVE is different

The study is based on the data for a single STEVE event on March 28, 2008 as tracked at the time by Canadian ground-based Themis All-Sky Imagers (ASIs) in Kapuskasing, Ontario and Sanikiluaq in Nunavut, as well as energetic particle detectors on an NOAA Polar Orbiting Environmental Satellite, POES‐17, that crossed over STEVE.


(Credit: Big Think/Google Maps)

At the top of the images below, taken a short while apart, we see what was being picked up in Nunavut as STEVE was being observed in Ontario, which appears at the bottom. In the third image, we see the track of the POES-17 as it crosses both STEVE—as signified by the small black star symbol—and the auroral activity over Sanikiluaq.


(Credit: B. Gallardo‐Lacourt /J. Liang /Y. Nishimura /E. Donovan)

It was the POES-17 that provided the critical information: “In the POES‐17 data, we did not observe protons and high‐energy electron precipitation. For low‐energy electrons (50 eV to 1 keV), we observed an increase in the flux. However, the integrated electron energy flux at that time was too low to be responsible for any optical structure and therefore not associated with STEVE. We assert that this observed STEVE event is not directly produced by particle precipitation at 800 km altitude." [800 km is the height of POES-17.]

So what could be causing STEVEs?

The authors of the study cite three possibilities. First, they say they can’t rule out that protons of lesser energy than they measured could have something to do with the ribbons of light. It could also be that STEVE is produced by some ionospheric process higher up, “similar to weak stable auroral red (SAR) arcs in the sub-auroral region.” The third possibility? Some process that’s completely unknown to science right now.

STEVE in Prince George, British Columbia, Canada (Photo: Ryan Sault)

Develop mindfulness to boost your creative intelligence

Sharon Salzberg, world-renowned mindfulness leader, teaches meditation at Big Think Edge.

Image: Big Think
Big Think Edge
  • Try meditation for the first time with this guided lesson or, if you already practice, enjoy being guided by a world-renowned meditation expert.
  • Sharon Salzberg teaches mindfulness meditation for Big Think Edge.
  • Subscribe to Big Think Edge before we launch on March 30 to get 20% off monthly and annual memberships.
Keep reading Show less

For a long time, the West shaped the world. That time is over.

The 21st century is experiencing an Asianization of politics, business, and culture.

Videos
  • Our theories about the world, even about history or the geopolitics of the present, tend to be shaped by Anglo perspectives of the Western industrial democracies, particularly those in the United States and the United Kingdom.
  • The West, however, is not united. Canada, for instance, acts in many ways that are not in line with American or British policies, particularly in regard to populism. Even if it were united, though, it would not represent most of the world's population.
  • European ideas, such as parliamentary democracy and civil service, spread across the world in the 19th century. In the 20th century, American values such as entrepreneurialism went global. In the 21st century, however, what we're seeing now is an Asianization — an Asian confidence that they can determine their own political systems, their own models, and adapt to their own circumstances.
Keep reading Show less

Vikings unwittingly made their swords stronger by trying to imbue them with spirits

They didn't know it, but the rituals of Iron Age Scandinavians turned their iron into steel.

Shutterstock
Culture & Religion
  • Iron Age Scandinavians only had access to poor quality iron, which put them at a tactical disadvantage against their neighbors.
  • To strengthen their swords, smiths used the bones of their dead ancestors and animals, hoping to transfer the spirit into their blades.
  • They couldn't have known that in so doing, they actually were forging a rudimentary form of steel.
Keep reading Show less

Why the ocean you know and love won’t exist in 50 years

Can sensitive coral reefs survive another human generation?

Videos
  • Coral reefs may not be able to survive another human decade because of the environmental stress we have placed on them, says author David Wallace-Wells. He posits that without meaningful changes to policies, the trend of them dying out, even in light of recent advances, will continue.
  • The World Wildlife Fund says that 60 percent of all vertebrate mammals have died since just 1970. On top of this, recent studies suggest that insect populations may have fallen by as much as 75 percent over the last few decades.
  • If it were not for our oceans, the planet would probably be already several degrees warmer than it is today due to the emissions we've expelled into the atmosphere.
Keep reading Show less