Amateur astronomers have found a new type of aurora borealis that looks like sand dunes and has been appropriately nicknamed “the dunes”. This new type of aurora is the result of gravity waves and oxygen atoms dancing in the night sky.
Interestingly, it was by pure chance that this new type of light show was discovered. When Minna Palmroth, who is a professor of computational space physics at the University of Helsinki, asked the public to send her pictures of the Northern Lights for an aurora guidebook, she was surprised to find that one of the photos taken in Finland didn’t match any previous known types of auroras.
“Then I realized that oh no ... I haven't seen these before,” Palmroth told Live Science in reference to the photo which captured the stripes that were spread so evenly. The majority of auroras extend upwards, but “the dunes” stretched out horizontally in smooth waves which had never been observed before.
“This is the first time these gravity waves are observed,” she said, adding, “In general the bores are rather a rare phenomenon.” The team was able to calculate that “the dunes” were approximately 62 miles up in the sky.
Scientists believe that “the dunes” illuminate a gravity wave that’s called mesospheric bores that are quite rare. When a gravity wave ends up being bent and caught between two cooler layers of atmosphere – the inversion layer (49.7 miles up) and the mesopause (62 miles up) – that’s when mesospheric bores happen.
The stripes in the aurora occur when the sun’s electrons stream into the waves and the folds that contain higher levels of oxygen which show brighter colors than those with little oxygen which ultimately causes the stripe patterns. The researchers’ study was published in the journal AGU Advances and can be read in full here.
“This is a very interesting observation,” Steven Miller, who is the deputy director of the Cooperative Institute for Research in the Atmosphere at Colorado State University, told Live Science, adding, “My first reaction when seeing the pictures were that those might be atmospheric gravity waves that are being ‘highlighted’ by the auroral activity — it appears that this is the hypothesis of the authors as well.” He went on to say, “I surmise that [these] ‘dunes’ are in fact a subset of a much more widespread region of atmospheric gravity waves that happen to be highlighted by the aurora.”
Pictures of “the dunes” can be seen here.
As exciting as this is, this isn’t the first time in recent years that a new type of light show has been discovered in the night sky. A “sky glow” named “STEVE” (Strong Thermal Emission Velocity Enhancement) was discovered and it was a non-aurora mysterious type of phenomenon. An aurora borealis typically shines green, blue or reddish colors, but STEVE is a slim beam of purplish-white light which extends up to 600 miles in the sky.