Aurora Hunters Have Discovered a New Type of Aurora Called ‘Dunes’

A group of aurora enthusiasts in Finland have discovered a new kind of aurora that scientists had never noticed or classified before. It’s called “the dunes,” and it’s being hailed as a boon to scientific research about a mysterious layer of Earth’s atmosphere.

The story of “the dunes” discovery is a great example of collaboration between enthusiasts and scientists. It started when a group of aurora enthusiasts from the Facebook group Taivaanvahti approached Minna Palmroth—a space physicist at the University of Helsinki—asking her to put together a field guide explaining the different types of aurora and the physics behind them.

Palmroth obliged, publishing a guidebook titled Revontuli — Bongarin Opas, but in October of 2018 the group came back to her and said she’d left one type of aurora out of her guide. She hadn’t… they had actually discovered a whole new kind of auroral.

Auroral dunes photographed on Oct 7, 2018 near Ruovesi, Finland. | Credit: Rami Valonen
Auroral dunes photographed on Oct 7, 2018 near Laitila, Finland. | Credit: Pirjo Koski

The dunes look like “fingers” extending horizontally toward the horizon, making them quite distinct from the usual auroral “curtains” that extend vertically. This is how the aurora hunters were able to spot the anomaly.

Shortly after the group pointed out the omission, Palmroth organized a group to go out and shoot the dunes from various locations at the same moment, helping her and her colleagues at the University of Helsinki determine more about this phenomenon.

They now know that the dunes are formed in a thin layer around 100 kilometers (60 miles) above sea level, and speculate that they’re caused by a kind of atmospheric wave called “mesospheric bores.” According to a press release published by AGU, the dunes are particularly special because will allow scientists to study a part of the Earth’s atmosphere that’s difficult to reach: too high for weather balloons or planes, but too low for satellites to properly observe.

Auroral dunes photographed on Oct 7, 2018 near Laitila, Finland (top) and Ruovesi, Finland (bottom). The two photographs were taken simultaneously. The dunes, marked by magenta circles and numbers, extend equatorward from the discrete bright arc in the north.
Credit: AGU Advances/Palmroth et al.

The discovery was finally published as part of a research paper in AGU Advances last month, alongside the pictures and videos of the phenomenon seen above.

The scientific potential of the discovery is fascinating, but for photographers, it means something else entirely: it’s time to go back through all of those old Aurora photos and see if you’ve ever captured the dunes for yourself.

Have you ever photographed Auroral dunes?

(via Duluth News Tribune and DIY Photography)

Image credits: All photos and videos used courtesy of AGU, photo credit in captions.

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