A new form of the northern lights has been captured by amateur enthusiasts, researchers have revealed.

The phenomenon of glowing green lights rippling across the night sky, also known as the aurora borealis, have long captivated the public and experts alike.

Some have suggested the lights are depicted in prehistoric cave paintings, while the Latin term is said to have been coined by the astronomer Galileo Galilei.

Auroras are produced when charged particles, such as electrons, are ejected by the sun and funnelled towards the Earth’s poles by our planet’s magnetic field. There they interact with gases in the atmosphere, including oxygen and nitrogen, increasing the energy of these gases – energy which is subsequently released as light.

“This is the same as neon lamps,” said Minna Palmroth, a professor of computational space physics at the University of Helsinki. “Basically we can say the auroras are celestial neon lamps.”

The northern lights have been seen in many forms, including “quiet arcs”, spirals and corona.

But now, thanks to the work of amateur enthusiasts, Palmroth and colleagues say they have discovered a previously unknown form, a pattern they claim resembles sand dunes.

The discovery came about when Palmroth was invited to join a Facebook group for aurora enthusiasts to explain the science behind the different forms of the phenomenon.

“Over the years I noticed that I am always explaining the same thing,” she said, adding that her experience spurred her to write a book. “It is similar [to] a bird-watching book, but instead of birds you take the aurora forms.”

As part of the project Palmroth asked the community of citizen scientists to capture images of particular forms. But there was a conundrum. “Some of them asked me ‘what about these stripes, which form are they?’,” she said.

With the pattern apparently new to scientific literature, Palmroth asked the citizen scientists to take further images of the aurora. “I was basically sitting on my couch and sending real-time messages to the observers saying ‘take these kinds of pictures’.” The community did not disappoint – the images sent included two taken at the same time from different sites in Finland.

That allowed Palmroth and colleagues to determine the altitude and other aspects of the phenomenon, such as the spacing between the ripples of the “dunes”.

Palmroth said the green colour of the display is produced by excited oxygen, with further work revealing its form is probably down to disturbances in the atmosphere, known as gravity waves – these are the same sort of ripples that form when a pebble is tossed into a pond. In the atmosphere, however, waves often travel vertically upwards – and there are many of them. That, said Palmroth, offered a clue.

“[The waves] have different frequencies, different wavelengths, different amplitudes and [so] to observe something very even, like the dunes, means that there has to be some active mechanism which is making them so even,” she said.

Palmroth explained that mechanism could be an unusual event called a mesospheric bore, whereby a particular wave is filtered out and bent, allowing it to travel horizontally between two layers in the atmosphere.

The phenomenon, she said, is similar to a tidal bore seen in rivers. Palmroth said this can happen when, unusually, the temperature of one layer of the atmosphere is slightly higher than both the layers above it and below it.

The dune-like appearance of the aurora, the team say, is down to the wave producing peaks and troughs in the density of oxygen.

“When this inversion layer is forming [in] these places where you can also have the aurora, then you can see the dunes,” added Palmroth.

Details of the discovery are published in the journal AGU Advances.

• The subheading of this article was amended on 29 January 2020 to remove the suggestion that the discovery itself was made by people in a Facebook group.