Mysterious Aurora-Like Purple Lights Are Solved by Citizen Scientists

Wednesday, 14 March 2018 - 6:48PM
Earth
NASA
Wednesday, 14 March 2018 - 6:48PM
Mysterious Aurora-Like Purple Lights Are Solved by Citizen Scientists
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NASA/Krista Trinder
When a series of purple lights with flourishes of green appeared in the northern hemisphere, professionals and amateurs alike immediately knew two things: it looked sort of like an aurora borealis, but was most certainly not a typical aurora.

For one, these lights appeared much closer to the equator than normal, had a different shape and vastly different color scheme (auroras tend to be heavy with greens, reds, and blues, not purple), and could last anywhere from 20 minutes to a full hour. Their nature remained largely a mystery until some citizen scientists and hobbyists began photographing the purple lights over a period from 2015 to 2016. 

Thanks to these hobbyists, a number of different sightings were brought together. The purple lights were given the funny nickname "Steve" before a new study in Science Advances created the more official-sounding name of "Strong Thermal Emission Velocity Enhancement", or "S.T.E.V.E." for short. And now we have a slightly better idea of what we're looking at. Meet Steve:



Citizen scientists, who are non-professional but valuable contributors to scientific fields, were among the first to document Steve and report their sightings to groups like the Alberta Aurora Chasers on Facebook (where the "Steve" nickname was first created) and the wonderfully named Aurorasaurus database.

But it was coincidence when one citizen, Notanee Bourassa from Regina, Canada, recorded a Steve sighting on the same night that a SWARM satellite from the European Space Agency was flying overhead and caught a view of STEVE from above. By combining all this data together, it became clear that the formation of Steve is very different from the formation of a normal aurora.

While both are caused by the collision of the Sun's charged particles with Earth's magnetic field, Steve travels along different magnetic field lines and is made up of hot particles called "sub auroral ion drifts" (or SAID for short). Since the satellite wasn't taking any photos when it detected the SAIDs, there was no way of knowing these SAIDs and Steve were one and the same until the citizen photos came forward.



According to Liz MacDonald, a scientist at NASA's Goddard Space Flight Center and the leader of the Aurorasauras team, Steve can teach us a lot about our planet and its atmosphere. She said the following in an official statement from NASA:

Opening quote
"Steve can help us understand how the chemical and physical processes in Earth's upper atmosphere can sometimes have local noticeable effects in lower parts of Earth's atmosphere. This provides good insight on how Earth's system works as a whole."
Closing quote


So if you're ever in southern Canada and think you see an aurora borealis, and you think to yourself, "Aurora borealis? At this time of year? At this time of day? In this part of the world?"

Well, it might just be Steve.
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