There is a light in the night sky over Canada that confuses scientists. It looks like a white-purple ribbon. It is very hot and does not take long. And it's called STEVE.
STEVE: as in, Strong thermal emission speed improvement.
Scientists do not really know what triggers the atmospheric phenomenon that hobby photographers have known for decades in the night sky, but have recently moved into the focus of the researchers.
But in research published this week Geophysical Research Letters they state what it definitely is not. It is not an aurora
An aurora is a phenomenon that illuminates parts of the sky at high latitudes, such as green, blue caused or red. It has to do with electrons and protons from a region of the earth called the magnetosphere.
"Sometimes these charged, energetic particles are able to rain in the upper atmosphere of the Earth, and when they do, they produce those colors we call Aurora," says Bea Gallardo-Lacourt, space physicist at the University of California University of Calgary, who is one of the authors of the study.
So the researchers set out to find out if STEVE is caused by particle precipitation, the main feature of a polar light.
They searched satellite data archives for an instance when a satellite crossed an area with STEVE, and found a good example of a NOAA satellite at an event in eastern Canada in March 2008.
"We have not seen any evidence of these particles," said Gallardo-Lacourt. "That gave us the indication that STEVE may not be produced in the sense that an aurora is produced."
The study concludes that STEVE is "unique". from an aurora and "its sky could be generated by a new and fundamentally different mechanism in the ionosphere."
STEVE has more mysteries. She says it's unclear what STEVE produces, which is in a stream of very fast and hot gas. The scientists want to perform spectroscopic measurements of STEVE that help them to find out the altitude in the atmosphere in which they are formed.
And STEVE appears in lower latitudes than Auroras, Gallardo-Lacourt says, but Auroras and Steve may still have a relationship. She notes that STEVE "is usually associated with a lot of Aurora activity at higher latitudes." One of the questions we are studying is how the activity at higher latitudes of the ionosphere can help create the right conditions for STEVE. "
Gallardo-Lacourt says the scientific community learned of STEVE when a NASA scientist chatted with a group of amateur photographers called Alberta Aurora Chasers in 2016 ,
The Aurora hunters described the phenomenon as a "proton arc" that scientists did not consider accurate. So they asked the Aurora Chaser for another name and they chose Steve.
Before it was an acronym, it was a reference to a scene in Children's Film 2006 Over the Hedge .
Inside, a group of animals stands speechless next to what is for them another awe-inspiring phenomenon – a garden hedge.
"What is this thing?" a creature says. "I'm scared," another mumbled.
"I would be much less afraid if only I knew what it is called."
A squirrel bursts out, "Let's call it Steve." The animals breathe a sigh of relief
"I love the name," says Gallardo-Lacourt. "It shows the connection between citizen scientists and formal scientists."