North·BRADLYN'S BLOG

You'd be lucky to see these newly-discovered aurora in the night sky

We are no strangers to the brilliant lights that have been talked about for centuries. And now, there is a new type to add to the list — studied even further by citizen scientists snapping pictures at the exact same time.

The rare aurora 'dunes' flitter like sand blowing along a coastline

This image shows the auroral 'dunes' in the forefront, in whispy layers. The new type of auroral form is reminiscent of sand blowing along a coastline. (Kari Saari photo)

Here in the North, people are constantly amazed, surprised and delighted by vivid colours dancing across the sky.

Whether it's the first or the hundredth time you've been outside experiencing the aurora borealis, the lights get better every time.

These brilliant lights come in unique, picturesque forms like bands, arcs, coronas and rays.

And now, there is a new type to add to the list. It was discovered by accident by aurora hunters, and studied even further by citizen scientists across Finland who captured photos of it at the exact same time.

It's named "the dunes." This new auroral form is reminiscent of sand blowing along a coastline. They flitter in a thin layer along tens of kilometres and are rare to see — although it is possible to catch them here in the North. 

"One of the most memorable moments of our research collaboration was when the phenomenon appeared at that specific time and we were able to examine it in real-time," says Matti Helin, a northern lights and astronomy hobbyist in a press release from the University of Helsinki

What is happening in the atmosphere

Knowing what type of aurora you are looking at helps you understand what is happening in the atmosphere.

This is because you can directly correlate conditions to the type of aurora observed.

Back in 2018, Minna Palmroth, professor of computational space physics at the University of Helsinki, published a book for aurora borealis watchers called Revontulibongarin opas so that citizen scientists (aka everyone) could easily identify the aurora they were observing.

Soon after publication, a group of aurora hunters in Finland realized that one such phenomenon didn't fit into any of the categories and sent the images to Palmroth. 

Thus the research began and in October 2018, aurora observers co-ordinated their efforts to take multiple photographs of the same dunes from different locations in Finland and Sweden.

Two of those photos were actually taken at the exact same moment, in Laitila and Ruovesi, in southwest Finland.

Watch the dunes in action here: 

These photos were the building blocks for finding out where in the atmosphere the dunes are, and when they occur. 

As unique as fingerprints

Aurora borealis are never the exact same — they're a unique combination of solar radiation, electromagnetism, atmospheric gases and height.

This new type of auroral wave was discovered in the auroral mesosphere‐lower thermosphere‐ionosphere region — a difficult name for something called the "ignorosphere."

The ignorosphere is an environment that is highly variable and hard to observe from the ground. This area is also nearly impossible for spaceships to fly in because of the atmospheric conditions, making it one of the least explored areas. 

This area is often ignored because it's between 80 to 120 kilometres in the air, and is at 65 to 80 degrees latitude.

What a makes it an auroral dune?

When the dunes were first noticed, they were characterized by their uniqueness and changes in brightness.

"The differences in brightness within the dune waves could be due to either waves in the precipitating particles coming from space, or in the underlying atmospheric oxygen atoms," Palmroth said in the press release.

"We ended up proposing that the dunes are a result of increased oxygen atom density."

This image shows the region and production of the gravity wave (white waves) from the mesospheric bore. (Submitted by Jani Närhi)

So what about the shape?

Well, the study suggests the wispy shape is caused by a combination of a gravity wave — which moves through the atmosphere — and a temperature inversion which is a backwards change in temperature. 

That results in something called a mesospheric bore — a rare phenomenon. 

This means the dunes are from the perfect storm of conditions: oxygen atoms, solar winds and the mesospheric bore.

The dunes are very rare, so don't expect to see them when you go out aurora hunting.

Atmospheric conditions need to be perfect for the dunes to occur, and you may need to be further north than usual to spot them. However, people in the N.W.T., Yukon and Nunavut have the possibility to view them — especially if the auroral zone is prominent one night in communities located at higher latitudes. 

But if you are in the right spot at the right time and see these aurora dunes, you'll definitely want to snap a pic to brag about.

About the Author

Bradlyn Oakes

Meteorologist

Bradlyn Oakes, CBC North’s meteorologist, covers the weather and climate for the Canadian territories. You can catch her weekdays on CBC’s Northbeat at 6 pm MT. Have weather photos to share? Send them to bradlyn.oakes@cbc.ca.

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