Images of the aurora borealis showing the structured continuum emission. Credit: Courtesy Faculty of Science research team, University of Calgary.
A whitish, grey patch that sometimes appears in the night sky alongside the northern lights has been explained for the first time.
Improved camera technology has helped capture true colour images of the night sky, which has resulted in an article, exploring a ‘structured continuum emission’ that is associated with the aurora borealis.
Dr Emma Spanswick, PhD, lead author on the paper and an associate professor with the Department of Physics and Astronomy in the Faculty of Science at the University of Calgary, said: “You’d see this dynamic green aurora, you’d see some of the red aurora in the background and, all of a sudden, you’d see this structured – almost like a patch – grey-toned or white toned-emission connected to the aurora.
“So, the first response of any scientist is, ‘Well, what is that?’”
Spanswick says the white patch has been referenced in scientific papers before, but it has never been explained.
Her team’s paper concludes it’s “most certainly a heat source” and says it suggests that the aurora borealis are more complex than previously thought.
STEVE and the northern lights
Spanswick says the discovery was made possible because an advancement in camera technology allows both amateur photographers and scientists to see true colour images of the night sky.
She said: “Everyone has noticed the advancement in digital photography. Your cellphone can now take pictures of the aurora.
“That has flowed to the commercial sensor market now.
“Those types of sensors can now be found in more commercial, more robust sensors that we would use in science.”
The team’s research came after there was a renewed interest in continuum emission with the discovery and observations of the long, glowing ribbon of purple light known as STEVE – or Strong Thermal Emission Velocity Enhancement.
Spanswick said: “There are similarities between what we’re seeing now and STEVE [which] manifests itself as this mauve or grey-toned structure.
“To be honest, the elevation of the spectrum between the two is very similar but this, because of its association with dynamic aurora, it’s almost embedded in the aurora.
“It’s harder to pick out if you were to look at it, whereas STEVE is separate from the aurora – a big band crossing the sky.”
Significant
The latest research is also significant because it includes three UCalgary students, including undergraduate Josh Houghton who was initially hired as an intern on the project.
He said: “I was still learning things at the time. I had just started my internship, and I very quickly got involved. It’s just very, very cool.”
Spanswick says Houghton did a lot of the analysis on the research, which led to his participation in the Nature paper as an undergraduate student.
“He’s had one heck of an internship experience,” she said.
Houghton will continue the research as part of his undergrad honours thesis, before taking on his master’s degree at UCalgary next year.
The article is published in Nature Communications.
