Mysterious Ribbon of Light Called ‘STEVE’ Is a New Celestial Phenomenon

Rodiano Bonacci
Agosto 22, 2018

While amateur photographers have been documenting the phenomenon for decades, scientists only began to study it back in 2016. The light from STEVE was also showing up closer to the equator than the aurora, which can only be seen at high latitudes. They occur when the planet's magnetosphere has been disturbed by solar wind, forcing electrons and protons in those winds and in magnetospheric plasma into the upper atmosphere.

There, their energy is lost, giving out light in different colors as a result.

STEVE, though, proved to be something different. For a start, sightings are relatively rare: while traditional auroras can typically be seen on a nightly basis, STEVE only showed up a few times per year. When researchers presented data about the unusual lights at a 2016 scientific conference, a fellow space physicist proposed converting the name into the backronym STEVE, which stands for Strong Thermal Emission Velocity Enhancement, and the researchers adopted it. The first scientific study published on STEVE found a stream of fast-moving ions and super-hot electrons passing through the ionosphere right where STEVE was observed.

The photographers first thought the light ribbons were created by excited protons, but protons can only be photographed with special equipment. In the new study, Gallardo-Lacourt and her colleagues analyzed a STEVE event that happened over eastern Canada on March 28, 2008, using images from ground-based cameras that record auroras over North America.

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

"Right now, we know very little about it", Gallardo-Lacourt said.

There is a mystery lighting up the northern hemisphere - thin ribbons of glowing purple and green that have come to be known to photographers and scientists as "Steve".

'But for the scientists, it's completely unknown'.

The team compared images from ground-based cameras with data from the NOAA's Polar Orbiting Environmental Satellite 17 (POES-17), which was overhead at the time and can measure charged particles raining down towards Earth. This means the mechanism that produces Steve must be different from the mechanism that produces auroras.

In fact, rather than an aurora, we should be calling STEVE a "skyglow", the team suggests. Next will come further research into ions and electrons in the ionosphere, to figure out whether they're responsible for the lights or if something higher in the atmosphere is at work.

This paper is open access for 30 days. Please provide your name, the name of your publication, and your phone number. In the new University of Calgary study, Gallardo-Lacourt and her colleagues made a decision to use the data recorded that night to further investigate Steve's mysterious origins.

Bea Gallardo-Lacourt, J. Liang, E. Donovan: Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada; Y. Nishimura: Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, U.S.A., and Department of Electrical and Computer Engineering and Center for Space Physics, Boston University, Boston, Massachusetts, U.S.A.

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