Meet STEVE, the northern lights in mauve

Citizen scientists captured images of a new type of aurora

This is a new kind of aurora that can appear in the sky during displays of the northern lights. It is a purplish and green band of light known as STEVE.

KRISTA TRINDER

Have you seen STEVE? An aurora is a brilliant light display that can show up at night in Earth’s upper northern and southern latitudes. STEVE is a new and nontraditional type. This aurora can drape the sky with a reddish-purple ribbon and bedazzling green bling.

Auroras form when charged particles interact with Earth’s atmosphere.

Citizen scientists in Canada recently discovered and photographed STEVE. Now the phenomenon has been explained — sort of. To do this, researchers made measurements from ground-based cameras. They also enlisted help from a satellite that passed STEVE when it was in full swing. The streak of color showed up to the south of the main aurora.

Scientists now suspect that STEVE may be a visible version of a typically invisible process that involves drifting charged particles, or ions. These ions move at high speeds through Earth’s upper atmosphere. They form a stream of particles with a strong flow. Researchers described what they observed in Science Advances on March 14.

It’s still not clear how STEVE’s glow arises from this flow, note Elizabeth MacDonald and her colleagues. MacDonald is a physicist at NASA’s Goddard Space Flight Center in Greenbelt, Md. She was a coauthor of the new study.

Its air of mystery hasn’t kept people from giving the phenomenon a scientific name. Citizen scientists had been studying this aurora as part of a project called Aurorasaurus. They named it “Steve” before its association with ion drift was known. MacDonald and colleagues decided to keep the name. They just turned it into an acronym for Strong Thermal Emission Velocity Enhancement.

The rest of us, though, can just call it STEVE.

Physics writer Emily Conover studied physics at the University of Chicago. She loves physics for its ability to reveal the secret rules about how stuff works, from tiny atoms to the vast cosmos.

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