STEVE may be even less like typical auroras than scientists thought 

Image credit: Elfiehall @ Wikipedia

More unexplained goings-on as the solar wind’s charged particles reach Earth’s ionosphere. For the latest photos showing bright green light, see the source article here.
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The purple-and-green, atmospheric light show nicknamed STEVE just got even stranger, says Science News.

STEVE, short for Strong Thermal Emission Velocity Enhancement, is a sky glow that appears south of the northern lights (SN: 3/15/18).

STEVE’s main feature is a mauve band of light formed by a stream of plasma flowing westward through the atmosphere — a different phenomenon from the one that gives rise to auroras (SN: 4/30/19).

But STEVE’s purple arc is often accompanied by a “picket fence” of vertical green stripes.

That fence looks similar enough to the shimmering green curtains seen in the aurora borealis that scientists thought at least this part of STEVE could be a type of aurora.

Recently, studies of the picket fence’s color have cast doubt on its origins.

Auroras form when electrons from the magnetic bubble, or magnetosphere, surrounding Earth cascade into the atmosphere (SN: 2/7/20). Those electrons make nitrogen in the air glow blue and oxygen glow green.

While STEVE’s green picket fence also contains glowing oxygen, a dearth of nitrogen emission hints that the fence is not the same kind of light show as an aurora.

Now, researchers and citizen scientists have identified an even more unusual aspect of STEVE’s picket fence: small green streaks that stick out like feet from the bottom of some of its vertical stripes.

The structure of these horizontal streaks cannot be formed by the electron showers responsible for auroras, researchers report in the December AGU Advances.

Full article here.

via Tallbloke’s Talkshop

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November 13, 2020 at 12:24PM

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