Amateur astronomers discover a new form of aurora borealis that resembles sand dunes
Amateur astronomers have discovered a new form of aurora borealis that resembles sand dunes, caused by oxygen waves flowing through a stream of solar particles.
The uniformly green-colored light show spans more than 30 miles and is more than 60 miles in the mesosphere.
They were identified by chance after space physics Minna Palmroth of the University of Helsinki asked auroras observers to send photos for a book.
The fan highlighted the images of a particular aurora that did not seem to fit any known type: he called them ‘auroral dunes’.
Professor Minna Palmroth said they probably formed within the mesosphere and present an exciting opportunity to ‘investigate conditions in the upper atmosphere.’
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The auroral dunes appear as a pattern of waves dyed green and resembling a striped veil of clouds or dunes on a sandy beach.
The book was born from Palmroth’s cooperation with enthusiasts and the answers it provided to questions about the physics of the phenomenon.
“Each auroral form is like a fingerprint, typical only of a certain phenomenon in the auroral zone,” said Professor Palmroth.
A few days after the book was published, fans saw the unusual form again and immediately informed the teacher.
“One of the most memorable moments of our research collaboration was when the phenomenon appeared at that specific moment and we were able to examine it in real time,” says Matti Helin, a fan of astronomy and northern lights.
The phenomenon was photographed at the same time in both Laitila and Ruovesi, in southwestern Finland, with the same detail observed in both images.
Maxime Grandin, a postdoctoral researcher on the Palmroth team, identified the stars behind the broadcast and determined the azimuths and elevations of the stars with the help of the Stellarium astronomy software program.
This made it possible to use the stars as reference points when calculating the altitude and extent of the auroral phenomenon.
The team detected a total of seven similar ‘auroral dunes’ events where a camera recorded the same uniform wave pattern.
The part of the auroral zone where the electrically neutral atmosphere of the Earth meets the edge of space is an extremely challenging environment for satellites and other space instruments.
Palmroth says that is why it is one of the least studied places on our planet.
“Due to the difficulties in measuring atmospheric phenomena that occur between 50 and 75 miles of altitude, we sometimes call this area” the ignorosphere, “she says.
The dunes were observed precisely in that region of the auroral zone.
Very rarely, a wave of gravity that rises in the atmosphere can seep and bend to travel between mesopause and an inversion layer formed intermittently under mesopause.
“The differences in brightness within the dune waves could be due to waves in precipitating particles that come from space, or in the underlying atmospheric oxygen atoms,” says Palmroth.
“We end up proposing that they are the result of a higher density of oxygen atoms.”
Next, the team had to determine how the variability in the density of oxygen atoms caused by gravity waves in the atmosphere results in such a uniform and extended wave field.
Normally, at study altitude, there are many different types of gravity waves that travel in different directions at different wavelengths.
The team describes them as a “mesospheric hole”, a rare event that takes place in the mesosphere and is similar to the rivers where the tide travels through the canal.
When the oxygen atoms in the hole collide with the electrons that rush into the atmosphere, they get excited.
By releasing this excitement, they create the auroral light.
The team described the aurora as a sand dune on a beach with a constant pattern of waves
“The auroral area as a whole is generally ruled out in drilling-centered studies, since auroral emissions impair the technique used to identify mesospheric holes,” said Professor Palmroth.
With the help of measuring devices operated by the Finnish Meteorological Institute, it was discovered that the dunes occur simultaneously and in the same region where the electromagnetic energy that originates in space is transferred to the ‘ignorosphere’.
“This could mean that the energy transmitted from space to the ionosphere may be related to the creation of the investment layer in the mesosphere,” he said.
“In terms of physics, this would be a surprising discovery, as it would represent a new and previously unobserved mechanism of interaction between the ionosphere and the atmosphere.”
The ionosphere is a layer of charged particles that envelops the planet and extends more than 600 miles above the surface.
The research has been published in the magazine. AGU advances.
WHAT ARE THE AURORAS AND WHAT ACTIVATES THE AWESOME NATURAL SCREENS?
The Northern and Southern Lights are natural light shows activated in our atmosphere that are also known as ‘Auroras’.
There are two types of Aurora: Aurora Borealis, which means “dawn of the north,” and Aurora Australis, “dawn of the south.”
The screens light up when electrically charged particles from the sun enter Earth’s atmosphere.
There are two types of Aurora: Northern Lights (archive photo), which means “dawn of the north,” and Aurora Australis, “dawn of the south.” The screens light up when electrically charged particles from the sun enter Earth’s atmosphere.
Usually, particles, sometimes called solar storms, are deflected by the Earth’s magnetic field.
But during stronger storms they enter the atmosphere and collide with gas particles, including hydrogen and helium.
These collisions emit light. Auroral screens appear in many colors, although pale green and pink are common.