A mysterious whitish-grey patch that sometimes appears alongside the northern lights has been explained for the first time by researchers from the University of Calgary. The patch, which has been observed but never understood, has been linked to the aurora borealis and is the focus of a study recently published in Nature Communications on December 30.
The phenomenon is referred to as “structured continuum emission,” and it appears as a grey or white-toned emission, often blending with the dynamic green auroras and the red aurora in the background. Dr. Emma Spanswick, the lead author of the paper and an associate professor in the Department of Physics and Astronomy at the University of Calgary, explained the phenomenon:
“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.”
While the patch had been referenced in past scientific studies, its cause had remained a mystery until now. The researchers concluded that the grey patch is “most certainly a heat source,” indicating that the auroras may be more complex than previously understood.
Advancement in Technology Leads to Discovery
This discovery was made possible by significant advancements in camera technology, which now allow both amateur photographers and scientists to capture true-color images of the night sky. Dr. Spanswick highlighted how digital photography has improved: “Your cellphone can now take pictures of the aurora. That has flowed to the commercial sensor market now.”
These advanced commercial sensors, which are also used in scientific research, enabled the team to observe the previously elusive grey emission associated with the aurora.
Similarities to the “STEVE” Phenomenon
The research also draws parallels to STEVE (Strong Thermal Emission Velocity Enhancement), a glowing ribbon of purple light recently discovered in the aurora. Both phenomena share similarities in their spectrum, though the newly identified grey patch is more closely embedded in the dynamic aurora. In contrast, STEVE appears as a separate, distinct band across the sky, making it easier to observe.
Dr. Spanswick explained the distinction: “STEVE manifests itself as this mauve or grey-toned structure… because of its association with dynamic aurora, it’s almost embedded in the aurora. It’s harder to pick out.”
Contribution from Students
The research also highlights the involvement of three University of Calgary students, including Josh Houghton, who was an undergraduate intern when he first joined the project. Houghton’s significant contributions to the data analysis were instrumental in the findings, and his work led to his inclusion as an author in the Nature Communications paper.
Houghton, now continuing the research as part of his undergraduate honors thesis, will also pursue his master’s degree at UCalgary next year. “It’s just very, very cool,” he said, reflecting on his experience.
Support for the Study
The research was enabled by the Transition Region Explorer (TREx) project, a UCalgary initiative jointly funded by the Canadian Foundation for Innovation, the Government of Alberta, and the Canadian Space Agency. The TREx instruments, including the RGB and Spectograph instruments, are maintained and operated by Space Environment Canada with support from the Canadian Space Agency’s Geospace Observatory initiative.
Implications and Future Research
This discovery offers a new perspective on auroral phenomena and demonstrates the growing complexity of the aurora borealis. Future research may explore the interactions between the aurora and the heat sources identified in this study, providing more insights into Earth’s space weather and magnetic interactions.
The findings also pave the way for future investigations of dynamic auroral features and their potential connections to the broader atmospheric processes that influence both Earth and other planets.
