A New 'Wave' Of Northern Lights Has Been Spotted. What Do 'Auroral Dunes' Tell Us About Earth?

Get yourself up to the Arctic Circle if you want to see “auroral dunes,” a new phenomenon in the night sky just discovered by amateur photographers in Finland. 

A new research paper published today in the journal AGU Advances makes official sightings of “auroral dunes,” which are believed to be caused by waves of oxygen atoms glowing in the Earth’s atmosphere.

This time-lapse video shows exactly what they look like:

What are the Northern Lights? 

They’re visible proof of Earth’s magnetic field. Electrically charged particles from the sun flow out into the solar system. This “solar wind” strikes Earth’s magnetic field and get funnel down magnetic field lines, with those particles exciting nitrogen and oxygen molecules in Earth’s ionised upper atmosphere, the ionosphere. The light given off is the aurora borealis, or Northern Lights. 

Earth's magnetic field is generated in its metallic core. There are liquid iron alloys flowing in its outer core, and as Earth rotates, it generates electric currents, and so, a magnetic field.

What are ‘auroral dunes?’

A green-tinged and even pattern of waves resembling a striped veil of clouds or dunes on a sandy beach. Their origins have been tracked to a wave guide formed within Earth’s mesosphere (above the stratosphere, between about 50-80 km up) and its boundary, the mesopause. The study suggests that “auroral dunes” could be helpful for researchers investigating conditions in Earth’s upper atmosphere.

The researchers calculated that “auroral dunes” occur at a relatively low altitude of 100 km with each wave field measuring 45 km.

Where do ‘auroral dunes’ occur?

Earth’s mesosphere – where our atmosphere meets space – is one of the least studied places on our planet. It’s challenging for satellites to study. “Due to the difficulties in measuring the atmospheric phenomena occurring between 80 and 120 kilometres in altitude, we sometimes call this area ‘the ignorosphere,’” said Minna Palmroth, Professor of Computational Space Physics at the University of Helsinki. She heads a research group developing the world's most accurate simulation of the near-Earth space and space weather that cause auroral emissions. 

“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,” says Palmroth. “We ended up proposing that the dunes are a result of increased oxygen atom density.”

The research suggests that “auroral dunes” are linked to rarely detected “mesospheric bores.” They resemble the tidal bore common to many rivers—where the tide travels up the river channel—with “mesospheric bores” gravity waves that are filtered as they rise through the mesopause. 

"This could mean that the energy transmitted from space to the ionosphere may be linked with the creation of the inversion layer in the mesosphere," says Palmroth. “In terms of physics, this would be an astounding discovery, as it would represent a new and previously unobserved mechanism of interaction between the ionosphere and the atmosphere.”

Where were ‘auroral dunes’ seen?

Laitila and Ruovesi in southwest Finland, where the phenomenon was photographed simultaneously. Cameras have recorded the same even pattern of waves seven times. 

When and where to see the Northern Lights

Between October and March each year when the nights are long and dark in the north polar regions of our planet, something incredible happens. Nightly displays of the Northern Lights are common around 64º to 70º North latitudes, though you need a clear sky to see them—and that’s why people often come home from Northern Lights-hunting trips disappointed. The answer, of course, is to hang around for as long as possible waiting for a clear sky in these locations: 

• Alaska
• Northern Canada
• Iceland
• Lapland (northern Norway, Sweden, and Finland)
• Northern Russia

Wishing you clear skies and wide eyes