Ever since aurora chasers discovered Steve, a mysterious ribbon of purple light in the night sky, scientists have wondered whether it might have a sec

Swarm helps discover Steve's long-lost twin

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2024-06-15 02:00:07

Ever since aurora chasers discovered Steve, a mysterious ribbon of purple light in the night sky, scientists have wondered whether it might have a secret twin. Now, thanks to a photographer’s keen eye, and data from ESA’s Swarm satellites, we may have found it.

Steve was a sensation when scientists stumbled across it a few years ago, thanks to the eagle eyes and excellent photography of the Alberta Aurora Chasers Facebook group.

But its mauve hue and fleeting appearance meant it couldn’t be a feature of the aurora borealis, commonly known as the northern lights, which comes in shades of green, blue and red and can last for hours. So, what could it be?

It turned out that Steve was a fast-moving stream of extremely hot gas called a sub-auroral ion drift. Or, to give Steve its full name, a strong thermal emission velocity enhancement.

Steve makes its appearance at dusk (before midnight) when the fast-moving stream of extremely hot gases move westward. But at dawn (after midnight), we also know that there’s an equivalent stream moving eastward.

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