The mysterious aurora known as ‘Steve,’ explained
by Adam Wernick
A composite of images captures “Steve” (Strong Thermal Emission Velocity Enhancement) over Manitoba, Canada. / NASA Goddard Space Flight Center
Thanks to collaboration between citizen scientists and astronomers, a strange phenomenon in the night sky, dubbed “Steve,” has finally been explained.
In 2017, a glowing purple-and-green ribbon across the heavens mystified sky-watchers because it showed up much further south than the famous northern lights, or aurora borealis. These observers decided to call it “Steve,” echoing the woodland creatures in the children’s movie “Over the Hedge.”
For a time, nobody knew what Steve actually was or what caused it. Now there’s a bona fide scientific explanation, according to NASA space scientist Liz MacDonald.
“Steve is a new type of aurora structure that can be seen in the northern or southern sky further south than the usual aurora,” MacDonald explains. “What we now know from the satellite observations is that this structure is associated with a very strong flow of the charged particles in the upper atmosphere that you can actually see when you’re looking at Steve. That signature from the satellite observations — this very narrow, long, purple arc — is actually something that scientists know and have studied for a long time. It’s something called a sub-auroral ion drift.”