An unusual celestial phenomenon called STEVE has been scrutinized by researchers. Originally thought to be a type of aurora, scientists have confirmed that the thin ribbons of purple and white light appearing in the night sky are an entirely separate phenomenon.
Amateur photographers have been capturing STEVE for decades but it only in the past few years that serious scientific analysis has been made. Astronomers compared images of STEVE with typical aurora images and realized there was a significant difference.
STEVE is a new phenomenon
Auroras occur when charged rain showers fall down into Earth’s upper atmosphere. “Our main conclusion is that STEVE is not an Aurora,” said Bea Gallardo-Lacourt, a space physicist at the University of Calgary in Canada and lead author of the new study.
“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.”
For the moment, scientists have dubbed STEVE a ‘skyglow’ that is distinct from an aurora. STEVE will now be subject to more rigorous scientific investigation to better understand the upper atmosphere and the processes generating this light in the sky.
“This is really interesting because we haven’t figured it out and when you get a new problem, it’s always exciting,” said Joe Borovsky, a space physicist at the Space Science Institute in Los Alamos, New Mexico who was not connected to the new study. “It’s like you think you know everything and it turns out you don’t.”
Amateur aurora chasers first documented STEVE
STEVE was first brought to the world's attention via a Facebook group called the Alberta Aurora Chasers. They had noticed bright, thin streams of white and purple light running East to West in the Canadian night sky when they photographed the aurora.
The group noticed that unlike the auroras which are visible every night of the year if weather conditions permit, STEVE was only visible occasionally. The aurora devotees called the ribbons of light “Steve” in reference to the 2006 film Over the Hedge.
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In 2016, when researchers presented information about the unusual sky event, another scientist suggested changing Steve to STEVE, an acronym for Strong Thermal Emission Velocity Enhancement. Several scientific papers have been published on STEVE, the first of which found a stream of fast-moving ions and super-hot electrons passing through the ionosphere right where STEVE was observed.
The researchers guessed that these particles are in some way connected to STEVE but could not confirm how they could produce the spectacular visuals. This new study has confirmed STEVE is not an Aurora and the next phase of research will be dedicated to determining what causes STEVE and why.
The American Geophysical Union (AGU)’s Geophysical Research Letters published the new study.