STEVE may be even less like typical auroras than scientists thought 

Posted: November 13, 2020 by oldbrew in atmosphere, Electro-magnetism, solar system dynamics
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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.
– – –
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.

Comments
  1. tom0mason says:

    More settled science of thermal emissions in the atmosphere.

  2. BoyfromTottenham says:

    But will it let me talk around the world (alright – far beyond the horizon then) on VHF ham radio like sunspots sometimes do?

  3. oldbrew says:

    AUGUST 20, 2018

    New kind of aurora is not an aurora at all
    by American Geophysical Union

    The study’s results suggest STEVE is an entirely new phenomenon distinct from typical auroras. The POES-17 satellite detected no charged particles raining down to the ionosphere during the STEVE event, which means it is likely produced by an entirely different mechanism, according to the authors.

    The researchers said STEVE is a new kind of optical phenomenon they call “skyglow.”

    https://phys.org/news/2018-08-kind-aurora.html
    – – –
    AGU study: Based on our results, we assert that STEVE is likely related to an ionospheric process; however, at this point, we are not able to evaluate the magnetospheric contributions responsible for the formation of STEVE.

    https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078509
    – – –
    Identifying the magnetospheric driver of STEVE (2019)

    Abstract: For the first time, we identify the magnetospheric driver of STEVE, east-west-aligned
    narrow emissions in the subauroral region.
    . . .
    Which instabilities are active is a challenging question and will require further investigation with more conjugate observations

    ‘https://arxiv.org/ftp/arxiv/papers/1906/1906.08886.pdf’

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