Aurora Events: What They Are and Why They Happen

Published on March 23rd, 2015 | by Brandon Ramsey in Science


In specific areas of the Northern and Southern hemispheres, there occurs a type of event in the sky known as an Aurora. These displays produce beautiful colors in the sky and while they may seem unnatural, they are in fact a natural event.

While you can’t see these events all over the world many people who live in far north or far south locations see them throughout the year. Join us as we examine these events and explain how and why they occur.

We’ll talk about where you can see them, and we’ll talk about where they happen and why. Let’s begin.

What Are These Events?

These events, sometimes referred to as northern or southern lights, are in fact natural light displays that occur in the Earth’s atmosphere. The scientific name for them is Latin for “sunrise.”

The name also refers to the Roman goddess of the dawn. These events typically occur in far north or far south regions of the Earth’s Northern and Southern hemispheres. The light that we see in the sky is caused by particles that are charged, specifically electrons and protons, entering the atmosphere from above.

The northern lights are referred to as borealis and the southern lights are referred to as australis. Various cultures have different beliefs for why these events occurred. For example the Inuit tribe believed that they could see their ancestors dancing inside of the flickering lights.

In Norse mythology they believed that these northern lights were a fire bridge to the sky that was built by the gods. Now that we know how these lights look and how they’ve been interpreted throughout history, it’s time to figure out why they occur and how.

Aurora_Borealis_and_Australis_Poster

By The original uploader was 14jbella at English Wikipedia (Transferred from en.wikipedia to Commons.) [CC BY-SA 1.0 (http://creativecommons.org/licenses/by-sa/1.0)], via Wikimedia Commons

What Causes These Atmospheric Events?

Would you believe me if I told you that our sun, which is 93,000,000 miles away, is responsible for these events? It’s true, while these lights do occur inside of Earth’s atmosphere, they originate out in space specifically from solar storms that send charged particles towards our planet.

More often than not Earth is in the path of these charged particles that come from solar storms.  When these particles reach Earth they interact with the planets natural magnetic field. These particles interact with various molecules and atoms inside of Earth’s atmosphere which causes them to become excited. This “excitement” is what causes them to light up.

When we say that an atom is excited we don’t mean that in the sense of an emotion. An atom’s structure consists of a central nucleus and the surrounding cloud of electrons that orbit the nucleus in the center. When the charged particles hit the atoms in Earth’s atmosphere, the electrons in those atoms move upwards to higher energy orbits which causes them to be more distant from the nucleus.

When electrons move back to a lower energy orbit they release a particle of light known as a photon. These atmospheric lights are very similar to what happens when you turn on a neon light for example. In these types of lights electricity is used to excite atoms in the neon gas that’s contained inside glass tubes. When the neon gas becomes excited it gives off a light and that’s how you get the colors.

These northern lights work in a similar fashion however its much larger. When we see them they typically appear to us in either arcs or spirals. They can also appear as curtains in the sky. When it comes to the colors that we see they come in various forms. In most cases they’re green, but sometimes you see pink, red, violet, or white.

Your location in terms of latitude determines whether or not you can see these lights in the sky. For example in the north near the Arctic Ocean the lights can be seen in places like Canada or Alaska and in Scandinavian countries like Iceland and Greenland in addition to the far east like Russia.

In some cases the lights can be seen in more southern latitudes inside the United States. Of course the lights also occur in southern areas near the south pole such as Antarctica.

In the past the reason for these various colors was a mystery. Eventually we discovered that various gases in the Earth’s atmosphere give off different colors when the atoms within are excited. For example, oxygen is responsible for giving off the green color that you see, and nitrogen is known to cause blue or red colors.

People travel from all over the world to see these displays. While you may understand exactly what causes them, that doesn’t take away the fact that they are still incredibly captivating events.

Significant Atmospheric Events Throughout History

1865 painting Aurora Borealis

A Painting of the Aurora Borealis by Frederic Edwin Churhc in 1865.

 

There were two specific events that occurred on August 28 and September 2 in the year 1859 that are thought to be among the most spectacular ones in our recorded history. These events were the result of a solar storm that year known as the Carrington event.

This event was a powerful geomagnetic storm that occurred during solar cycle 10. Between the two aforementioned dates, numerous sunspots were spotted on the sun. On August 29th for example, the southern lights were observed as far north as Queensland Australia.

On September 1st two amateur astronomers by the names of Richard Carrington and Richard Hodgson made the first observation of a solar flare. This display resulted in a massive coronal mass ejection that traveled directly toward Earth and took over 17 hours to make the journey of 93,000,000 miles.

More recent studies of these solar flares and storm events have shown that a modern storm of this magnitude would cause widespread problems for people in our modern civilization. A storm in 2012 matched this magnitude, but it did not hit the earth directly.

The most visually pleasing aspect of these storms and solar flares is of course the light that we see in the sky, but extremely strong events can disrupt electronics or even fry them entirely.

As a result of the solar flare spotted by Carrington and Hodgson, the North and South lights were extremely widespread, bright and seen in places that they would normally be seen. A report in the New York Times from Boston on Friday, September 2, 1859  claimed that “the light was so brilliant that at about 1 o’clock ordinary print be read by the light.”

This specific event was the first time in history that the lights in the sky and electricity were linked together. Not only were the lights responsible for this discovery but there was also 125,000 miles of telegraph lines that were interrupted for many hours during the course of the storm.

Some of these telegraph lines, however, were the exact length and orientation to allow for what is known as a geomagnetically induced current. This current was the result of the electromagnetic field that was created during the event. During this time these telegraph lines were able to continue communicating with each other even with their power sources turned off.

For over two hours of conversation between Portland and Boston continued despite the fact that they had no battery-powered all. This event was reported in the Boston Traveler on the following day.

Theories, Superstitions, and Mythological Explanations for These Events

The first realization of the magnetic distortion that occurs during these events was mentioned by an ancient Greek explorer and geographer named Pytheas. It was also mentioned in other times throughout history including evidence in 1741 that showed large magnetic fluctuations occurring during the time that an event was observed in the sky.

Over the course of history there been multiple superstitions and theories sometimes based on fact and sometimes based on mythology or superstition. Let’s examine some of these now.

A Roman philosopher by the name of Seneca spoke in his first book regarding these events drawing his observations from Aristotle. He asked whether or not the events occurred above or below the clouds.

He also spoke of the story where an aurora formed above Ostia that was extremely intense and bright red so much so that a member of the Army stationed nearby for firemen duty fled to the city thinking that it was on fire.

Walter William Bryant wrote in his book Kepler that Tycho Brahe “recommended sulfur to cure infectious diseases brought on by the sulfurous vapors of the aurora borealis.”

Benjamin Franklin himself had a theory on his “mystery of the northern lights” that they were caused by a concentration of electrical charges in both the north and south poles of the earth that was exacerbated by snow and other moisture in the atmosphere.

The names of these events also change throughout history. The Cree, for example called them “dance of the spirits.” In Europe during the medieval era these lights were believed to be signs from God himself.

in Norse mythology there was a claim that explain how these events occurred:

“the Valkyrior are warlike virgins, mounted upon horses and armed with helmets and spears. When they ride forth on their errand, their armor sheds a strange flickering light, which flashes up over the northern skies, making what men call the “aurora borealis”, or “Northern lights.”

This explanation is incredibly detailed, however there isn’t much evidence to show that the old Norse literature and mythology actually had this explanation for the events. It is true that these events occur commonly over places in Scandinavia and Iceland, but it’s believed that the magnetic North Pole was considered to be much further away than this region during the time periods of Norse mythology.

As mentioned earlier, in Roman mythology the scientific name refers to the Goddess of the Dawn. Among the aboriginal Australians the southern lights are commonly referred to as “ashes” or “fires” of the dead.

During the Civil War after the Battle of Fredericksburg, lights could be seen in the sky that led the soldiers to believe that God was on their side because it was very rare to see such lights as south as Virginia.

Do Events Like These Occur on Other Planets?

Besides Earth both Jupiter and Saturn also have magnetic fields. These fields are much stronger than Earth’s with Jupiter’s for example being 4.3 Gauss compared to Earth’s 0.3 Gauss. Both of these other planets in our solar system also have extremely large radiation belts.

800px-The_Aurora_Borealis_or_Northern_Lights_shine_above_Bear_Lake_in_Alaska_050910-F-MS415-009

Northern lights above Bear Lake, Alaska

 

Because of this auroras have been seen on both planets through the Hubble space telescope. In addition to these two planets Uranus and Neptune have also been known to have these events.

On these foreign planets the lights appear to be created in the same method as a result of solar wind. In the case of Jupiter, its moons, specifically Io, are responsible for most of the light events in its atmosphere. This is caused by electric currents that occur along field lines. These currents are the result of what is known as a dynamo mechanism created from the motion of the rotating planet and the moving moon.

Many of these moons themselves have also been known to have these events: Io, Europa, and Ganymede have all been known to have light events in their atmospheres as seen by the Hubble space telescope.

Final Thoughts

The science behind these aurora events may seem simple, but it is in fact a very complex mechanism. While we understand what causes the color and location of these events, there are still times that they baffle even modern scientists.

Despite not knowing the entire physical process that creates these events, we do know much of what makes them happen. It is remarkable that Earth is able to display these lights as it requires a very complex set of processes to be in place.

Were it not for the Earth’s magnetic field, or the particles in the atmosphere, or the solar winds that originate from the sun, we would not have these incredible displays. It is highly recommended that at some point in everyone’s lives, that they witness one of these events firsthand.

Thank you as always for reading and be sure to tell us about your experiences with these northern and/or southern lights in the comments below.

 



About the Author
Brandon Ramsey

Brandon Ramsey is the head author and editor of The Time Now Blog. Be sure to follow us via social media!


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