Wednesday, August 22, 2018

Speaking of Science: Steve, we hardly knew ye

Speaking of Science
Talk nerdy to us

Alberta Aurora Chasers capture STEVE, the new-to-science upper atmospheric phenomenon, on the evening of April 10, 2018, in Prince George, British Columbia. (Ryan Sault)

In 2017, a group of Canadian skygazers photographed a bright natural phenomenon in the night sky: a strip of purplish-white green light. One of the aurora chasers named it Steve, a reference to the 2006 animated movie "Over the Hedge." Steve turned out to be a relatively common feature of the northern sky, but, as The Washington Post reported last year, it was new to scientists.

The name STEVE stuck, and astronomers worked it into an acronym, Strong Thermal Emission Velocity Enhancement. STEVE was believed to be an aurora, and a study in March revealed a stream of superhot electrons above the ribbon of light. A study published this week in Geophysical Research Letters, however, indicates it is not what scientists thought.

A STEVE event occurred March 28, 2008. Cameras designed to capture auroras caught the event, and physicists recently probed this data for a particle rain, a telltale sign of auroras. After the sun belches energetic particles our way, the shower of particles that tangos with Earth's atmosphere generates photons, which we see as light.

That particle rain was absent, per the camera records: "We did not observe protons and high‐energy electron precipitation," the authors wrote in the new study.


"Our main conclusion is that STEVE is not an aurora," Bea Gallardo-Lacourt, an author of the study and a physicist at the University of Calgary in Canada, said in a statement. They are now calling STEVE a skyglow, not related to an aurora.

What produces this skyglow? Well, the authors of the new research are not quite sure. "A new and fundamentally different mechanism in the ionosphere" could be making STEVE, they speculated. But it remains unexplained what that mechanism is.


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