Is an aurora still that impressive if it’s invisible?
THE northern Lights, also known as auroras, are well known for their stunning displays of shimmering color, a delight to the human eye. They are also extremely interesting to science, as they are created by intense charged particles streaming in from the sun and interacting with the earth’s atmosphere.
Now, scientists have found another aurora here on Earth, but unlike the more well-known northern lights, this one doesn’t put on a show for humans. In fact, it is completely invisible to the naked eye.
Researchers led by Earth scientist Katrina Bossert at Arizona State University just observed an aurora shining in infrared light, created by the interaction of these energetic cosmic particles and carbon dioxide in Earth’s atmosphere. “This offers a new way to observe Earth’s aurora from space. Different auroral emissions can be associated with different altitudes and particle energies,” Bossert said in a statement.
Related: Where to see the Northern Lights: Guide to the Northern Lights 2023
“The discovery of Dr. Bossert’s paper is extremely important because it not only provides us with new means to study the aurora, but also a deeper understanding of how the space environment and Earth’s upper atmosphere are intertwined,” says the geophysicist at the University of Alaska Fairbanks Doğacan Su Öztürkthat he was not involved in the new job.
The earth’s atmosphere it’s like a layer cake, with the bottom, densest layer near the surface (the troposphere, where it occurs most of the time) and the softest layers on top. The thermosphere and ionosphere overlap, two of the highest layers between 80 and 700 kilometers above the earth’s surface. This is where the Karman line that defines the edge of space exists, approximately 62 miles (100 km), and typical colored auroras occur between 62 and 155 miles (100 to 250 km) high as a result of atomic oxygen colliding with energetic particles from the space.
The infrared aurora Bossert found, however, is the result of carbon dioxide. Although we usually think of it as a greenhouse gas, it exists in multiple layers of the earth’s atmosphere. Its aurora occurs a little lower than the others, about 90 kilometers. The team observed this aurora with NASA AIRS toolthe infrared atmospheric sounder, on board the Terra Aqua observation satellite. This orbiter was launched way back in 2002 and has been collecting data about Earth ever since.
Observing the auroras from space has a few distinct advantages; from the ground, scientists can’t see auroras during daylight and are limited in the amount of sky a telescope can cover. AIRS, on the other hand, has been observing infrared energy, including that of the aurora, every day for years. This dataset spans over 20 years and will be invaluable for future aurora studies. “It’s very exciting to see the aurora in a different way,” says Bossert.
The auroras are an important window into Earth’s atmosphere for scientists, and there’s still a lot we don’t know about how the cosmic environment interacts with the upper layers of our atmosphere.
Studies like this give scientists a better picture of “when and where auroral activity is occurring,” says Öztürk. They are also trying to understand “how far energetic particles can get in the Earth’s atmosphere,” says Bossert. It is not yet known how the carbon dioxide aurora also varies with the seasons, which could be related to fluctuations in carbon dioxide levels in the atmosphere.
In addition to the large dataset, Bossert and his team revealed new information about the upper atmosphere: that energetic particles funneled towards Earth by our magnetic field deposit their energy by slamming into carbon dioxide molecules.
“This will help us understand the mechanisms that generate large-scale disturbances that travel around the world,” adds Öztürk. Understanding the aurora will also help create more accurate space weather forecasts, so hopefully you’ll never be caught in an aurora solar storm Still!
Their findings were recently published in the journal Geophysical Research Letters.
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Image Source : www.space.com