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Meet ‘STEVE’: The Purple Sky Glow That’s A Completely New, Unknown Phenomenon

Aug 22, 2018 11:16 PM EDT
Unlike the photographed aurora, STEVE consists of purple and white lights that appear much more rarely. Much about it is a mystery, even to scientists who are well-versed in atmospheric processes.
(Photo : Noel Bauza | Pixabay)

The strange dancing purple glow dubbed STEVE has mesmerized sky watching enthusiasts for decades. Scientists don't know what this mysterious phenomenon is.

It's not, as it turns out, an aurora as previously believed. An aurora is the effect of electrically charged particles that collide in the Earth's atmosphere.

Instead, STEVE is an entirely new celestial phenomenon that's still largely a mystery in and beyond the scientific community, according to a report from the American Geophysical Union.

Not An Aurora

In a new study published in the journal Geophysical Research Letters, researchers analyzed a STEVE event that occurred in March 2008 in an attempt to figure out the phenomenon's nature. The team didn't quite find out what it is, but they did realize that it doesn't share the same atmospheric process with aurora events.

"Our main conclusion is that STEVE is not an aurora," Bea Gallardo-Lacourt, study lead author and a space physicist at the University of Calgary, says in a statement. "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."

The researchers detected no charged particles dropping to the ionosphere during the STEVE event that they observed, suggesting that the phenomenon is produced by a different mechanism than an aurora. For now, the scientists are referring to STEVE as a "skyglow."

This skyglow appears to consist of hot gas that is about 3,000 degrees Celsius (5,430 degrees Fahrenheit), Motherboard reports.

History, Future Of STEVE

Amateur auroral photographers were the first ones to really bring attention to STEVE, specifically the members of a Facebook group called the Alberta Aurora Chasers. STEVE, vibrant streams of purple and white light, reportedly showed up in the Canadian sky going from east to west.

The name "Steve" was adopted from the film Over the Hedge, but when researchers presented the unusual phenomenon at a scientific conference in 2016, another scientist suggested to change it to the backronym STEVE for Strong Thermal Emission Velocity Enhancement.

Unlike aurora, which can be seen anytime there is a clear evening sky, STEVE is only visible a few times every year. The latter also gets much closer to the equator.

The photographers initially believed that excited protons were causing the striking phenomenon, but if this were the case, it would have to be photographed using special equipment.

Now that they know what STEVE isn't, scientists are excited at the prospect of studying something entirely new to the community.

"Probably the most important question to answer now is: if STEVE is not produced by precipitating particles (like aurora), how is the structure being created?" Gallardo-Lacourt tells Motherboard in an email. "To answer this we need simulations (modeling the physics involved) that could help us understand all the dynamics that are playing a role."

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