A strange yet pretty natural phenomenon appeared on Canadian sky. At first it might appear just like an arc of lights floating on the sky just like aurora, however there was a particularly big difference between it and conventional aurora.
While conventional aurora usually appears as green or bluish lights on the sky, the color of this strange light phenomenon was purple. The strange phenomenon has been given name STEVE, the acronym of Strong Thermal Emission Velocity Enhancement.
The discovery of this natural phenomenon was actually started from a Facebook group. A group of aurora watchers who are the members of Facebook group Alberta Aurora Catchers habitually take pictures of aurora lightshow in the sky and upload the results to the Facebook group’s page.
In one 2018 winter night, some members noticed a strange form of lights in the sky. They were not sure about what kind of phenomenon it was and thought that albeit showing different colors from ordinary aurora this was another kind of aurora
What is it actually and how special is this light show? We will talk about the purple aurora in this article.
Purple Not Proton
At first, they thought that this natural phenomenon was another kind of another sky phenomenon called ‘proton aurora’. Because of that, they first named it as ‘proton arc’, based on the shape of this purple aurora.
However, they spotted some differences between what so-called proton aurora and this purple aurora. Mainly is because proton aurora invisible to naked eyes. Proton aurora is actually a kind of northern lights that happens when protons, instead of electrons, are colliding with gases in Earth’s atmosphere, thus the name.
Eric Donovan, a professor at University of Calgary who first stated that it was not an ordinary proton aurora in 2017. “They pulled up this beautiful photograph of this thing. And I’m like, ‘I don’t know what that is, but it’s not the proton aurora,” said Donovan to New York Times in 2017.
He and his team started a study to learn more about it after he spotted the difference. Using data from European Space Agency, some photographs, and GPS coordinates, he learned that both phenomena were clearly different.
Over The Hedge
Knowing that the sky phenomenon was clearly different from any other kinds of light phenomenon in the sky that they have ever watched, they thought that they need to give it a name. One of Alberta Aurora Chasers member, Chris Ratzlaff, suggested the name STEVE in 2017 because of there were not sufficient data explaining the phenomenon.
This naming itself was based on a character in 2006 animated comedy movie ‘Over The Hedge’, depicting something completely unknown. The name however, was pretty much suitable for the phenomenon since it is the acronym of a nice explanation about what it was.
‘STEVE’ also describes the mysteriousness of the animated character it was named after. For your information, in that movie, the animal characters gave the name ‘Steve’ to a row of shrubs that was confronting them without any clear picture about what it actually was.
But what is actually the purple sky phenomenon called STEVE? Is this just another aurora that appears in different color, or is it a rare sky phenomenon that occurs because of global warming and climate change that happens in our age? Apparently, Donovan and his team might have found the answer for it.
The mystery being kept hidden by STEVE was solved by Donovan and his colleagues after a year of study. In his paper, Donovan described that STEVE was a kind of sub-auroral ion drift or SAID. It was actually a phenomenon when ionic gas travels quickly across the horizon.
Purple Arc
STEVE, in its appearance showed an incredible lightshow similar to aurora borealis or the northern lights. However, it is slightly thinner, comes in different color, and appears further south than ordinary northern lights.
Different from aurora borealis that appears to be like layers of lights dancing in the sky, STEVE shows itself in a shape of a single thin purple arc stretching from east to west. Thus, although it usually appears along the northern lights, people can still easily distinguish it.
If it is to be described, based on the data collected by scientists, the phenomenon was actually a wide ribbon of hot gasses in the altitude of about 450 kilometers above earth’s surface. Being charged by solar particles, it interacts in almost similar way to aurora borealis toward earth’s magnetic field.
The hot gasses flow in the speed of 6 kilometers per second and created a 25 kilometers wide area of effect along its trail. Although it may appear soothing and tranquil, but actually the trail of gas is very hot. The temperature caused by the movement of ionized gas can reach up to 3000 degrees Celsius.
Not Much Attention
Steve is not a new thing for us, actually, but most of the time, we don’t pay enough attention to this phenomenon and just ignore the presence. Nobody had ever gotten into that much details about STEVE before it became a viral content in the internet.
The reason was that such phenomenon has never shown its existence as obvious as it was in recent years, which become new mystery for the scientists. “SAIDs don’t really have any visual features, so the relationship between them and something as visually stunning as Steve is super fascinating,” said Ratzlaff, the name giver.
However, for NASA, the presence of this celestial lightshow has been recognized for almost a half century. “It’s something that we know that’s actually been studied for 40 years,” said Elizabeth A. MacDonald, NASA’s Goddard Space Flight Center space physicist.
But recent lively appearance in northern part of the world has drawn huge attention to STEVE and NASA decided to work together with Alberta Aurora Chasers and other aurora watcher groups to know it better. They collect the works of amateurs all over the world about sky phenomena in a server called Aurorasaurus which is then to be assessed by MacDonald and teams.
The idea of crowdsourcing is actually a great help for the scientists to collect necessary data and evidences to learn about STEVE. “I think of it as a disruptive innovation. Something unexpected that changes the way you look at things,” said MacDonald.
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