Citizen Stargazers Help Solve Purple Light Mystery

A group of "citizen scientists" helped solve a mystery surrounding ribbons of strange purple light in the sky that has become known as the aurora "Steve." 

Aurora watchers located primarily in southern Canada captured photos of the ribbons of purple light, nicknamed Steve by the Calgary Aurora Watchers, between 2015 and 2016, according to a NASA press release. The amateur scientists shared their findings with each other online and with a team of real scientists that head a project called Aurorasaurus.

Research published Wednesday in Science Advances indicate that "Steve may be an extraordinary puzzle piece in painting a better picture of how Earth's magnetic fields function and interact with charged particles in space," NASA notes. 

"This is a light display that we can observe over thousands of kilometers from the ground,” said Liz MacDonald, head of Aurorasaurus and a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It corresponds to something happening way out in space. Gathering more data points on STEVE will help us understand more about its behavior and its influence on space weather.”

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The purple color from Steve and the more commonly observed green, blue and red auroras all come from charged particles from the sun that collide with the earth's magnetic field. The researchers determined that Steve differs from typical auroras that grace the polar skies because the fast-moving "hot" particles known as sub auroral ion drift, or SAID, travel through a different magnetic field at lower altitudes. 

"That means the charged particles that create Steve connect to magnetic field lines that are closer to Earth's equator, hence why Steve is often seen in southern Canada," NASA notes. 

Scientists have been studying SAIDs since the early 1970s, but this is the first time they have linked the phenomenon with visual confirmation. 

"People have studied a lot of SAIDs, but we never knew it had a visible light. Now our cameras are sensitive enough to pick it up and people's eyes and intellect were critical in noticing its importance," said Eric Donovan, a co-author of the study. 

The researchers at Auroroasaurus decided to continue to call the aurora Steve in homage to the amateur researchers who initially discovered and documented the phenomenon, but now STEVE stands for Strong Thermal Emission Velocity Enhancement.