The natural light display of the Aurora has been one of the most magnificent sights on our planet. People from across the world travel just to witness it. But what is the definition of Aurora? What makes an Aurora remarkable? What causes the colorful lights that it is known for? Hint: it involves the Sun. Let us read on to know more.
Definition of Aurora: What is an Aurora?
Definition of Aurora:
a natural light display in our night sky
an atmospheric phenomenon consisting of bands, arcs, and streamers seen in different colors
cockcrow, dawn, first light, daylight, light, sun, sunrise, sunup, day, daybreak, morn, morning
Middle English from the Latin aurōra, meaning dawn
An aurora is a beautiful sky phenomenon that never fails to amaze people all around the world. These lights are often seen in a distinct green color. However, they also come in other shades like pink, yellow, violet, red, white, and even blue.
Italian astronomer Galileo Galilei called the lights aurora borealis. This name was inspired by Aurora, the Roman goddess of the dawn. Her Greek counterpart is Eos. The word Boreas is the north wind’s Greek name.
The plural for aurora is aurorae (ə-rôr ′ ē) or simply auroras. These great colors are also called polar lights. That is because the light shows are observed in high latitudes, or places near the Arctic and the Antarctic.
At The Ends Of The World
The displays from both poles are distinct from each other. Those that we see near the Arctic Circle in the northern hemisphere are called the northern lights. Scientifically, they are called aurora borealis. Auroral displays from the southern hemisphere are commonly known as the southern lights. They are also called aurora australis.
The magnificence of the aurora is a sight not everyone has the opportunity to see every day. Aside from being location-specific, the weather should also be perfect to see such a perfect event.
The aurorae have fascinated generations for years. It became a part of the lives of people in the past as they make sense of the natural world. Alluring myths and stories surround this light show.
It involves stories of the afterlife and that of heroism and greatness. It affected their way of living as some took it as an omen while others saw it as good luck. There are also some stories that explained the origin of this phenomenon.
The process that makes aurora borealis and aurora australis possible happens constantly. These shimmering lights are not a seasonal thing. Also, they can even happen in the daytime. But why can’t we see them all the time?
Knowing the science behind it will shed light on the why, when, and where of the aurorae.
Definition of Aurora: Why It Happens
The Sun plays an important role in our everyday lives. It makes photosynthesis possible, among other things. But aside from that, it also gives us the aurora. How so? The magic happens in the Earth’s atmosphere.
The magnetosphere is a region in our atmosphere. This area is dominated by the Earth’s magnetic field. It is like a big bubble that protects the Earth from the threats of cosmic rays and radiation, as well as the solar wind.
The magnetosphere is shaped like a comet. The area that faces the Sun is called the dayside. It is compressed due to the constant bombardment of the solar wind. This region is only about six to ten times the Earth’s radius. The other end of the magnetosphere, which looks like a tail, is called the nightside. It measures greater than the other side, extending to about hundreds of the Earth’s radius.
The Earth has the strongest magnetosphere among the terrestrial planets in our solar system. But planets are not the only ones that have the aurora phenomena. Brown dwarfs, moons, and even comets have them too.
The solar wind is what causes an aurora. With it comes a stream of charged particles, generally protons and electrons. When these particles react with our planet’s magnetic lines of force, a reaction happens.
To understand it better, let us take a look at an atom. According to NASA, “atoms are the building blocks of matter.” The center of an atom is called a nucleus. It contains protons (particles of positive charge) and neutrons (particles of neutral charge).
The nucleus is surrounded by electron shells. These shells have different energy levels. Electrons, or particles of a negative charge, move within these energy levels whenever they become excited.
Our atmosphere is made up of different gases. And these gases are made up of particles. When the solar wind strikes the atmosphere, the extra energy that it brings causes the atoms in the atmosphere to become excited. This means that the electrons in the atom particles move to a higher-energy electron shell.
But electrons do not remain excited for a long period of time. They will move back to their initial orbit or ground state. And when they return to an orbit with a lower energy level, a particle of light called a photon is released, and thus an aurora is produced.
To put it simply, in definition, an aurora is a natural light phenomenon in our sky that is a result of solar particles reacting with the particles of the Earth’s atmosphere. These streamers of light are in the upper atmosphere of our planet where the reaction takes place.
Different Types of Aurora
Auroras come in different colors and forms. Their occurrence also depends on the intensity of the solar activity.
The most common gases in our atmosphere are oxygen and nitrogen. Emissions from oxygen produce green and orange to red light. Nitrogen, on the other hand, can give us red, blue, or purple auroral lights. The colors depend on the amount of energy that was absorbed.
Aside from that, altitude also affects the color of the auroras.
The gases in the atmosphere are not the only factor that plays in the formation of auroras. The energy transferred from the Sun is another agent that affects the phenomena. A coronal mass ejection increases the intensity of the solar wind, resulting in a more auroral activity. The lights appear brighter and more frequent during such phases.
Auroral displays are never the same. The patterns and shapes vary just as much as their colors. Our location and perspective as observers also affect how we see these forms.
When to See the Aurora
A dark sky is our ally in observing the ethereal display of the auroras. That means, we cannot see them with broad daylight as our backdrop. The exact “when” of the appearance of these light shows in the sky is, however, unpredictable. The process relies strongly on the Sun’s activity.
One such activity is the solar cycle. So what is it and how does it affect our auroral sightings?
The Solar Cycle
The magnetic field of the Sun goes through a process called the solar cycle. It lasts for about 11 years. This affects the Sun’s surface and its activities. The start of this process is called a solar minimum. It then builds up leading to the solar maximum, where solar activities become stronger. Eventually, it will go back to the solar minimum to start a new cycle.
Knowing about the solar cycle is important in determining the chance to see an aurora. The Sun has the most sunspots during the solar maximum. Solar flares and other eruptions on its surface become more common. These activities bombard particles towards our atmosphere in the form of solar wind. The stronger these winds are, the more prominent the auroral displays are in our sky. The last solar maximum was in April 2014.
We are already in Solar Cycle 25 as of 2021. The solar minimum was in December 2019 while the predicted maximum is in 2025.
It’s A Matter Of Timing
Although auroras are unpredictable, we can increase our chances of seeing them by checking the weather ahead. Even if the KP factor is good if the sky is blanketed with clouds, conditions will not be good for viewing. The first requirement is therefore a dark and clear sky. Other considerations to include are less light pollution.
People usually travel to see the Northern Lights from August to April. Auroral activities peak around the months of the equinoxes, in September and March. In the southern sky, the best months to see aurora australis is from March to September.
The natural light shows are usually observed around 6 pm to 4 am, with the best chance to see them from 10 pm to 11 pm.
There are times when Auroras can be observed as early as 4 pm. That is during the polar night or when the Sun does not rise above the horizon. This phenomenon is the opposite of the polar day (midnight sun) when the Sun shines above for more than 24 hours.
Places To See the Aurora
The best places to see auroras are near the polar regions. Why is it so? It is because the magnetic pressure is strongest in those areas. Since the magnetic activity is strong, it pulls the particles from the solar wind. These particles then excite the air molecules in the atmosphere which in turn emit light when they calm down.
The “auroral oval” covers the magnetic pole of the Earth. This is the region of the globe that displays the light show. The said oval changes from time to time. It expands when there is a great geomagnetic storm from the Sun. In such cases, the auroras can be seen in places of lower latitude.
The auroral zones for seeing the northern lights best are Norway, Finland, Sweden, Alaska, Iceland, Canada, Greenland, and Russia.
Much of the area near the south pole is occupied by the Southern Ocean. Even so, we can still see the southern lights in high southern latitudes. It can be seen in Australia (especially in Tasmania), New Zealand, Chile, Argentina, and of course in cold Antarctica.
Stories, Myths, and Beliefs About the Aurora
The glow of the aurorae has inspired many stories and myths across cultures. It was mentioned and described in the classical works of Seneca, Pytheas of Massalia, and Pliny the Elder.
According to some Inuit beliefs, the souls of their long-lost ancestors can be seen dancing through the ethereal lights. Below are other myths and legends associated with the phenomena.
Behind the Name
Aurora is a goddess from Roman mythology, representing the dawn. She brings in the light of the new day by riding her chariot and flying it across the sky. This way, she tells her brother and sister, the Sun and the Moon, that a new day is breaking.
It was a fine autumn day and Fubao was enjoying the breeze in the wilderness. The young woman suddenly saw a curious band of light in the sky. The light looked like a glowing halo of the Big Dipper. The Earth was illuminated with the light. Different forms of shapes and shadows looked like they had a life of their own.
Fubao was so moved by what she had witnessed that she became pregnant. She bore a son and named him Xuānyuán. He later became known as the Yellow Emperor. He became one of China’s cultural heroes. As the originator of the Chinese culture, the legendary monarch was also believed to be the father of all Chinese people.
The “magical band of light” in the story of Fubao was the northern lights.
Many stories and beliefs surround the northern lights among the Norse people. Some believe that the light display is a reflection of the armor of the Valkyries or female warriors. It is also interpreted as a fire bridge that the gods built.
Aurora borealis is also associated with many other things. Some believed that the lights were the children who died at birth. According to different folklore in Iceland, the lights will help mothers who are giving birth as it will ease the pain for them.
A famous story related to the northern lights involved the fire foxes. In Finland, they call the phenomenon revontulet, which means “fire fox.” According to the tale, the beautiful aurora borealis is produced when the Arctic foxes run so fast. They ran and ran and unknowingly brushed their tails against the mountain, producing the glow of the aurora.
The Lights as an Omen
The Sámi people believed that the northern lights are the spirits of the dead. They also took it as an omen. That belief also entails that they never talk about it fearing that doing so will make the lights aware of their presence. They are afraid that the aurora borealis will scoop them from above and carry them to the sky if they upset it. Some say it can slice a person’s head off! To avoid all these horrible things, they avoid going out of the house during the light displays.
Aboriginal Australian Beliefs
The southern lights have been known by many names among the indigenous peoples of Australia. They all have a common theme and that is the lights are commonly related to fire.
The Ngarrindjeri people believe that aurora australis are the campfires lit by the departed souls in the “Land of the Dead.” For the people in Queensland’s southwest area, the lights are the “feast fires” of the ghostly spirits called Oola Pikka. They believed that these spirits communicated to their Elders through the lights of the aurora.
Some even have local names for the phenomena. The Gunditjmara people called it puae buae which means “ashes.” For the Dieri people, aurora australis is related to an evil spirit that is responsible for creating a big fire in the sky. They called it kootchee.
More Facts and Features
- The aurora phenomenon shares its name with a city in Illinois and another one in Colorado, near Denver.
- Aurora borealis is usually around 90km to 130 km above the Earth’s surface. It was at its closest when it reached 80 km above the ground.
- The “great geomagnetic storm” of 1859 was said to be the strongest ever recorded. Because of that storm, the auroral displays were so strong that they disrupted the telegraph systems. That event led to the discovery of the strong effect of aurora on electricity.
- We already know that the Sun determines the auroral activity of our planet. Interestingly, as it undergoes the 11-year solar cycle, its magnetic field flips. Its north pole becomes the new south pole and vice versa. They will exchange places again after 11 years.
- An aurora-like phenomenon was given the name STEVE. It is short for “Strong Thermal Emission Velocity Enhancement.” This atmospheric optical phenomenon is a narrow arc that appears in purple and green color.
- While some feared the aurora, Swedish fishermen were eager to see it. They believed that the lights are a sign of a good catch, thinking that the aurora is a reflection of schools of fish.
- The gas giant Jupiter has auroras. The strongest contributor to this event on this planet is not the solar wind but its moon, Io.
- Auroras on Venus are different. This planet has no magnetic field. But the phenomenon still happens when the solar wind strikes the planet’s night-side atmosphere. Because of that, the light displays are more diffuse.