The findings, published on Dec. 30 in the journal Nature Communications, detail how this white patch appears as a structured, grey- or white-toned emission embedded within the colorful dynamic green and red auroras. Dr. Emma Spanswick, PhD, the study's lead author and associate professor in the Department of Physics and Astronomy, explained the origins of the discovery:
"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," she said. "So, the first response of any scientist is, 'Well, what is that?'"
Although this white patch has been noted in scientific literature before, no explanation had been established until now. Spanswick's team concluded that it is "most certainly a heat source," providing new insights into the complexity of the aurora borealis.
The study highlights how advancements in camera technology have played a critical role in capturing true-color images of the night sky, enabling researchers and amateur photographers alike to observe phenomena that were previously undetectable. Spanswick emphasized the impact of these technological developments:
"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," she said. "Those types of sensors can now be found in more commercial, more robust sensors that we would use in science."
The research was partially inspired by renewed interest in continuum emission, sparked by the discovery of STEVE (Strong Thermal Emission Velocity Enhancement), a glowing ribbon of purple light observed alongside auroras.
"There are similarities between what we're seeing now and STEVE," Spanswick explained. "STEVE 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."
The study also highlights the contributions of three University of Calgary students, including undergraduate Josh Houghton. Initially hired as an intern, Houghton's role quickly expanded to involve detailed data analysis, earning him co-authorship on the Nature Communications paper. Reflecting on his experience, Houghton 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 praised Houghton's efforts, noting, "He's had one heck of an internship experience." Houghton plans to continue this line of research for his undergraduate honors thesis and pursue a master's degree at UCalgary next year.
The research was supported by the Transition Region Explorer (TREx) project, funded by the Canadian Foundation for Innovation, the Government of Alberta, and the Canadian Space Agency. The TREx RGB and Spectrograph instruments are maintained by Space Environment Canada through the Canadian Space Agency's Geospace Observatory (GO) Canada initiative.
Research Report:Association of structured continuum emission with dynamic aurora
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