The Science Behind the Aurora Borealis
Imagine glancing up at the night sky and seeing a myriad of different colors and patterns shining down on you like remnants of a rainbow. Though they may seem daunting and unearthly at first, these gleaming lights are actually Auroras. Unfortunately, not many can say they have seen an aurora in person before, as these breathtaking phenomena occur much less frequently than we may hope. As they grace the sky with their beauty, auroras can create numerous different patterns that reinvigorate the night. Whether it be waves, streaking flares, or even crescents, the auroras illuminate the sky in a way that feels nothing short of magical. Radiant colors such as neon green, red, blue, and purple paint the starry night and create a true piece of art. While we could go on and on telling you about the splendor of these lights, the science behind them may just magnify your appreciation for these auroras all the more.
Now, the glaring question may have developed in your mind after hearing about all of the Auroras’ beauty: What are they?
The famous astronomer Galileo Galilei named these lights in 1616 as the aurora borealis after figures in both Roman and Greek mythology. The creation of auroras is intrinsically linked with the sun. The sun has many magnetic fields which at times can collide and mix together. When this occurs, sunspot regions are formed, usually more than one at a time. These regions can then eject large amounts of plasma particles, known as solar winds, into space and in turn, towards the earth. Now, the earth and its magnetic field usually protect us from particles often ejected from the sun, but solar storms consisting of these solar winds can be exceptionally powerful. When the solar winds pass by earth, some of the energy and particles in the can travel down earth’s magnetic field lines at the north and south poles, thus causing auroras.
‘Aurora’ is a broad term referring to all different types of auroras. Those found in the north pole, the northern lights, can also be referred to as aurora borealis. Those found in the south pole, the southern lights, can also be referred to as the aurora australis. Another term that may be used to describe auroras is the polar lights. Spending long periods of time in the south pole is a much more difficult task than in the north, thus it is often a tricky task to see the southern lights. It is easiest to see the northern lights during wintertime in upper Canada and Alaska, but many of the Nordic countries are also a great option. If you get lucky you may even be able to see the lights from New England, just like some European settlers did in 1719. Interestingly, when they were fortunate enough to see the northern lights for the first time it actually caused mass hysteria.
Auroras can take on many colors such as blue, red, purple, green, pink, and yellow. The color which emanates from a specific aurora can be a result of many different factors, such as particle type and altitude. While not always the case, oxygen particle collision often results in red, yellow, or green auroras. Contrastingly, nitrogen particle collision usually forms pink, blue, or purple auroras.
Altitude is also key in aurora coloration, as auroras above 150 miles high are typically red, while those just under 150 miles are often green. Auroras above 60 miles are usually blue, and those under 60 miles are often purple, with colors varying slightly in shade throughout. So if the sun emits solar winds into all of space, shouldn’t other planets experience auroras too?
Indeed! Earth is not the only planet that is blessed with stellar auroras. Any planet with a strong enough magnetic field can experience them, making Jupiter, Saturn, Uranus, and Neptune¹ prime candidates. It should be noted, though, that the exact details of the auroras on these planets are a bit different from Earth due to their distinct gaseous makeup and atmosphere. Regardless, both Jupiter and Saturn, for example, can be illuminated by bright blue lights at their poles. Surprisingly, planets such as Venus and Mars can also experience auroras even without a magnetic field. The Venusian ionosphere is able to induce a magnetic field that reaches out away from the sun and redirects particles onto the planet, thus creating auroras. Mars, on the other hand, creates auroras through magnetic fields embedded within the planet’s crust. The auroras on Mars are not exclusively located at the poles and are usually a faint blue.
No one truly knows when the first-ever aurora occurred. However, cave paintings in France from over 30 million years ago are among the first that depict them. Before people could identify that they were natural phenomena, some thought that auroras were signs of future destruction and war. Even before they were fully understood, philosophers had references to the northern lights in their work.
Aristotle described the lights he saw in the sky as “flames of a burning gas” in his book, Meteorology, written over 20 centuries ago. Auroras were also prominent in Greek and Roman mythology. The Greeks believed that the Aurora was the sister of the sun and moon, Helios and Sine, and that she traveled along the morning sky to tell her siblings of the new day coming. The Romans held similar thoughts, believing that these lights were the goddess of dawn named Aurora.
Auroras have also made a prominent impact on art. The piece, Aurora Borealis, by artist Frederic Edwin Church was inspired by sketches from polar explorer Isaac Israel Hayes, who saw the auroras as he escaped his frozen boat in the Arctic in 1861. When Hayes returned to New York from his journey, America was in the thick of the Civil War and the auroras commonly seen in the north were thought to be god displaying his displeasure with the confederacy for supporting slavery. Though the scientific aspect of auroras is well and truly great, the presence they have had in areas such as art and philosophy simply goes to show the widespread impact these glimmering lights have had throughout history.
While it may take some time until scientists fully understand the true complexity of aurora formation, we may sit back and relax here on earth while enjoying the undeniable beauty of the northern lights. If you are looking to get a more basic understanding of auroras, check out what NASA has to say about them here.
[1] Named “gas-giants” these four planets have extremely strong magnetic fields and dense atmospheres that promote the formation of auroras at their poles.
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Citations
- Andrew, E. (2019, March 11). What’s It Like To See Auroras On Other Planets? Retrieved October 6, 2020, from https://www.iflscience.com/space/what-s-it-see-auroras-other-planets/
- Staff, S. (2017, October 11). Northern Lights: What Causes the Aurora Borealis & Where to See It. Retrieved October 6, 2020, from https://www.space.com/15139-northern-lights-auroras-earth-facts-sdcmp.html
- The Great Northern Lights Panic of 1719. (2019, December 11). Retrieved October 6, 2020, from https://www.newenglandhistoricalsociety.com/great-northern-lights-panic-1719/
