Monday, April 24, 2017

Photographers Discover New Pseudo-Aurora, Get to Name the Phenomenon...End Up Calling it "Steve".

A group of "Aurora Chasers" in Canada appear to have stumbled on an extraordinary new astrophysical phenomenon, and—in typical internet fashion—endowed it with an amusingly ordinary name. Don't let the unassuming moniker fool you, though: Steve is a mind-bogglingly powerful event, albeit one that is apparently more common than scientists expected.

The stream of purple light arcing across the image is no ordinary aurora: meet "Steve".
Image Credit: ESA

While the phenomenon has been repeatedly spotted during aurora events, suggesting it's related to solar wind activity, the term "aurora" refers specifically to light generated by the interaction of solar wind particles with the atmosphere. But that's not what's going on here: Members of the group that discovered it originally referred to the bright streak as a "proton aurora", assuming it was similar in origin to the usual shimmering green glow created by electrons interacting with air. However, when protons slam into the atmosphere, they create light that's much too high-energy to be seen with the naked eye. Steve had to be something else.

Steve is also much higher than most aurorae—close to 200 miles above Earth's surface. The edge of the atmosphere, although it's not a hard-and-fast line, is about 60 miles up, although the most powerful of aurorae have been observed to reach as far as 600 miles into space.

Luckily, the phenomenon seems to be relatively common, and researchers at ESA—coordinating with citizen scientists around the world to locate another occurrence—managed to steer a satellite right through a stream, taking data as they did. The results are astounding: the gas appears to be moving at close to 13,000 miles per hour, in a stream roughly 15 miles wide. Temperature measurements suggest that it's at least 5000°F.
What's causing this incredible phenomenon? Scientists are being cagey about details until they publish, but it seems likely that it's a stream of solar wind plasma passing by the earth. The light might be emitted thanks to thermal effects, but synchrotron radiation due to its deflection by Earth's magnetic field is another possibility. 
The recent attention around the phenomenon has aurora chasers all over the world abuzz looking out for it. Since last year, there have been about fifty Steve sightings, but it's unclear whether this is an unusually high number or people are just now noticing it as a distinct phenomenon.
As a scientist and space enthusiast named Stephen, I have to say I'm friggin' thrilled about all this, but also extremely curious—is this really such a common occurrence, and we've just never noticed before? Or might the prevalence have increased in recent years, leading to its discovery? A citizen science project may be in order, sifting through old aurora photos to find earlier incidences of Steve.
Time and data will tell, and we'll keep you posted as we learn more about this awesome new phenomenon. 

Stephen Skolnick

P.S. The name "Steve" appears to have been inspired by this scene from the Dreamworks film "Over the Hedge"

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