The STEVE Aurora, a unique sky phenomenon seen in western Canada for years, finally has been explained in a paper published Wednesday in the journal Science Advances.
STEVE, short for Strong Thermal Emission Velocity Enhancement, looks like a ribbon of purple light with green accents and it happened in latitudes lower than regular auroras, website Space.com reported.
The distinctive aurora has given scientists a new look at the interactions of Earth's magnetic field and upper atmosphere.
"It's exciting because this might be a kind of aurora that more people can see than any other kind, because when it shows up, it shows up over more populated areas that are further to the south," said Elizabeth MacDonald, a researcher at NASA's Goddard Space Flight Center in Maryland and lead author of the new paper, per Space.com.
"It's an aspect related to [auroras] that's further south than we ever had recognized … It tells us that the processes creating the aurora are penetrating all the way into the inner magnetosphere, and so that's a new aspect of it."
NASA's Aurorasaurus team at its center in Maryland conferred to determine the identity of this mysterious phenomenon after citizen scientists watched it in the Canadian skies from 2015 to 2016, sharing reports and pictures along the way.
Along with amateur aurora watchers, STEVE was spotted by ground-based cameras from the University of Calgary and University of California, Berkeley, along with the European Space Agency's Swarm satellite.
"This is a light display that we can observe over thousands of kilometers from the ground," MacDonald said in a NASA statement. "It corresponds to something happening way out in space. Gathering more data points on STEVE will help us understand more about its behavior and its influence on space weather."
The Science Advances abstract said that from the Swarm satellite observations, STEVE revealed an unusual level of electron temperature enhancement and density depletion, along with a strong westward ion flow, indicating that a pronounced subauroral ion drift was associated with the aurora.
MacDonald said STEVE can help researchers understand how the chemical and physical processes in Earth's upper atmosphere can sometimes have local noticeable effects in lower parts of Earth's atmosphere and give "good insight on how Earth's system works as a whole."
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