Citizen Scientists Tracking Northern Lights Help Uncover New STEVE Feature

In 2018, a new aurora-type discovery hit the world. From 2015 to 2016, citizen scientists reported 30 cases of a purple ribbon in the sky, with a green fence structure underneath. Now called STEVE, or Strong Thermal Emission Velocity Enhancement, this phenomenon is still new to scientists, who are struggling to understand all the details. What they do know is that STEVE is not a normal aurora – some believe it may not be an aurora at all – and new discovery about streaking in structure brings scientists together of solving the mystery.

“Often in physics we develop our understanding and then test the extreme cases or test the cases in a different environment,” says Elizabeth MacDonald, space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “STEVE is different from the usual Northern Lights, but it is made of light and it is driven by the auroral system. By finding these tiny little streaks, we may be learning something fundamentally new in the way green auroral light can. be produced. “

These “tiny little streaks” are extraordinarily small dot-shaped elements in STEVE’s green fence. In a new paper for AGU Advances, the researchers share their latest findings on these points. They suggest the streaks could be moving points of light – elongated in footage due to cameras blur. The tip of the streak in one image will line up with the tip of the tail in the next image, contributing to this speculation by scientists. However, there are still a lot of questions to answer – whether the green light is a dot or a line is one more clue to help scientists understand what causes the green light.

“I’m not quite sure yet about anything about this phenomenon,” said Joshua Semeter, a professor at Boston University and the article’s first author. “You have other footage where it looks like there’s a tube-like structure that persists from frame to frame and doesn’t seem to conform to a moving point source, so we’re not. not really sure yet. “

STEVE as a whole is something scientists are still working to label. Scientists tend to classify the optical characteristics of the sky into two categories: the glow of the air and the aurora. When the glow from the air occurs at night, atoms in the atmosphere recombine and release some of their stored energy as light, creating bands of bright colors. By studying the patterns of the glow in the air, scientists can learn more about this area of ​​the atmosphere, the ionosphere. To be classified as an aurora, however, this release of light must be caused by electron bombardment. These characteristics are formed differently but also appear to be different: The glow of the air can occur across the Earth, while the auroras form in a large ring around the magnetic poles of the Earth.

“STEVE in general does not seem to fit well into either of these categories,” Semeter said. “The emissions come from mechanisms that we do not yet fully understand.”

STEVE’s purple emissions are likely the result of ions moving at supersonic speeds. Green emissions appear to be related to eddies, like the ones you might see forming in a river, moving slower than other waters around it. Green features also move slower than structures in purple emissions, and scientists believe they could be caused by turbulence in space particles – a shuffling of charged particles and a magnetic field, called plasma – at these altitudes. .

“We know that kind of turbulence happens. There are people who base their entire careers on studying turbulence in ionospheric plasma formed by very rapid flows.” Semeter said. “The evidence usually comes from radar measurements. We never have an optical signature.” Semeter suggests that when it comes to the onset of STEVE, the fluxes in these cases are so extreme that we can actually see them in the atmosphere.

“This document is the tip of the iceberg in this new area of ​​these tiny little pieces of fence. What we do in physics is try to get rid of it to improve our understanding,” MacDonald said. “This article establishes the altitude range and some of the techniques we can use to identify these features, and then they can be better addressed in other observations.”

To establish the altitude range and identify these characteristics, scientists made extensive use of photos and videos captured by citizen scientists.

“Citizen scientists are the ones who brought the STEVE phenomenon to the attention of scientists. Their photos are generally longer than our traditional scientific observations, ”MacDonald said. “Citizen scientists do not find themselves in the patterns that scientists enter. They do things differently. They are free to move the camera and take the exposure they want. However, to make this new discovery of dots within STEVE, photographers actually took shorter exposure photographs to capture this movement.

To get these photographs, citizen scientists spend hours in the freezing cold, late at night, waiting for the dawn – or hopefully STEVE – to appear. While the data may indicate whether an aurora will appear, the indicators for STEVE have not yet been identified. However, Aurora Hunters appear and still take pictures.

Neil Zeller, photographer and co-author of the article, says he did not originally plan to be a citizen scientist. “It was just for her beauty,” Zeller explained. Zeller has been involved in the discovery of STEVE from the start. He showed a photo he took of STEVE to MacDonald years ago, sparking the first research into the phenomenon. He is now co-author of this article.

“It’s an honor, it really is,” Zeller said of his contribution to this research. “I tend to take a step back from the scientists doing the job. I’m here for the beauty of it and to capture these phenomena in the sky.”

This article also drew on another valuable contribution from a citizen scientist: a database of volunteers on STEVE observations. Michael Hunnekuhl, another author of the article, maintains this database and has contributed to STEVE’s findings in the past. Hunnekuhl noticed the streaks in the photographs independently of the scientists on the paper, and his detailed recording and triangulation techniques played a central role in this research.

Zeller and other citizen scientists plan to continue taking and examining these images, capturing the beauty of Earth’s atmosphere, and MacDonald, Semeter and other scientists will continue to study them, finding out more about this new phenomenon.