If you happen to see a vertical ribbon of dancing, flickering purple light playing across the sky of the Northern Hemisphere, fear not. It's just Steve.
That's right — Steve. The hilarious placeholder name comes from the Alberta Aurora Chasers, a group of aurora enthusiasts who discovered the atmospheric phenomena in 2016. Unlike your standard aurora displays, which look like gently wafting curtains, Steve is more of a narrow arc of light.
The members settled on the unusual name in honor of the 2006 animated film "Over the Hedge," in which some woodland creatures name an unknown object "Steve" to make it appear less frightening.
Steve may appear similar to other auroras because it lights up the night sky when the sun's charged particles interact with Earth's magnetic fields. But Steve is definitely in a class of his own — especially with the spectacular show of dancing purple lights.
How is Steve different?
Well first and foremost, Steve actually isn't an aurora. Although researchers speculated for years that Steve was like other auroras due to its location and movements, a 2018 study negates that idea. When Steve appeared in March 2018, NOAA's Polar Orbiting Environmental Satellite 17 measured for charged particles in the sky around Steve. No charged particles were detected. Therefore, the process for creating Steve isn't the same for auroras.
"Our results verify that this STEVE event is clearly distinct from the aurora since it is characterized by the absence of particle precipitation," said the study's author Bea Gallardo-Lacourt. "Interestingly, its skyglow could be generated by a new and fundamentally different mechanism in the ionosphere."
So, what do we know for sure about Steve?
Steve travels along the sub auroral zone (lower latitudes closer to the equator) while other auroras are found at higher latitudes — thus giving it its unique purple hues. "Steve might be the only visual clue that exists to show a chemical or physical connection between the higher latitude auroral zone and lower latitude sub auroral zone," said NASA's Liz MacDonald.
On average, Steve can be seen about 20 km vertically (north-south direction) and 2,100 km horizontally (east-west direction), according to another study conducted in 2019 by Gallardo-Lacourt and her team. They also discovered Steve only lasts about an hour and usually only occurs after substorms — a disturbance in the magnetosphere when energy from Earth's "tail" enters the ionosphere.
The purple lights are made up of "a fast moving stream of extremely hot particles called a sub auroral ion drift, or SAID." "People have studied a lot of SAIDs, but we never knew it had a visible light. Now our cameras are sensitive enough to pick it up and people's eyes and intellect were critical in noticing its importance," said NASA's Eric Donovan.
To investigate the phenomena, Donovan combed over data captured by a trio of ESA satellites called Swarm. Located in two different polar orbits, the three satellites are constantly recording measurements of the strength, direction and variations of the Earth's magnetic field. To Donovan's delight, one of the satellites recently passed through a visit by Steve and captured its unique characteristics.
"The temperature 300 km above Earth’s surface jumped by 3000°C and the data revealed a 25 km-wide (15.5-mile) ribbon of gas flowing westwards at about 6 km/s compared to a speed of about 10 m/s either side of the ribbon," he said in an ESA press statement.
As you can see in the photos below, Steve isn't at all frightening; it's just plain beautiful.
Steve was spotted on Sept. 7, 2017 over Owen Sound, Ontario, Canada. (Photo: Northern Lights Graffiti/Flickr)
The photographer notes Steve began as a fountain of white light in the west and stretched across the sky meeting a band of light from the east directly above at about 90 degrees, drifting south. (Photo: Rocky Raybell/Flickr)
While Steve is mostly purple, it also produces some green lights. (Photo: james_stone76/Shutterstock)
NASA is asking for help with Steve. If you think you've spotted Steve, you can submit your photos and video to aurorasaurus.org or download the app. NASA also has tips on how you can know if you've seen Steve.
Editor's note: This article has been updated since it was originally published in April 2017.