Whether you’ve seen the northern lights in person or just seen them in pictures and videos, one question probably lingers: How do auroras form?
The famous Galileo Galilei first coined the term “aurora borealis” in the year 1619. He chose the name after Aurora, the Roman goddess who governed the morning. But long before the term existed, people were fascinated and confused by this phenomenon that they sometimes saw in the night sky.
The first time the aurora was ever written about, to our knowledge, was in China in 2600 BC. People have attributed the phenomenon to everything from candles above the clouds to the reflection of sunlight.
However, the scientific facts are just as interesting as the folklore.
In this guide, I’ll show you exactly why and how the northern lights appear in the sky.
Keep reading for a deeper appreciation of one of the night sky’s most beautiful shows!
What Causes the Northern Lights?
To understand the Aurora, we have to start at the sun.
The sun sits at the centre of the solar system. This yellow star is responsible for all the life on our planet – it’s kind of a big deal. And it’s also responsible for the northern lights.
When the sun rotates on its axis, its magnetic fields become distorted and twisted. Sometimes, those fields get tangled up together, which results in a burst that creates what we know as sunspots.
Sunspots appear as temporary darker areas on the surface of the sun. In these places, the magnetic field is thousands of times stronger than that of the Earth. The sunspots tend to appear in pairs, and can be many times larger than the Earth itself.
The centre of the sun reaches an incredible 27 million degrees Fahrenheit. However, its surface temperature tends to fluctuate. This causes the surface to bubble and boil. In this process, particles escape through the sunspots. These plasma particles, also called solar wind, get sent through space to Earth.
The northern lights are the result of this solar wind plunging into Earth’s atmosphere. It takes just 40 hours for the particles to reach Earth from the sun and create an aurora borealis.
Auroras Around the Solar System
Auroras aren’t limited just to Earth. Other planets in our solar system – and possibly planets outside of it – also experience this phenomenon.
The solar system’s gas giants – Jupiter, Saturn, Uranus, and Neptune – have the strong magnetic fields and thick, strong atmospheres needed to make the auroras appear. However, since the conditions are different on each planet, the auroras appear differently on each one.
Venus also has auroras, which are created by the stretched magnetic field of the planet. Although the atmosphere on Mars is too thin to experience a global aurora, it does have local auroras, thanks to its own magnetic fields in the planet’s crust.
The Aurora Cycle
Some years the auroras are more prominent than others. What causes these fluctuations?
Solar storms and sunspots contribute to more striking displays of northern lights. The peaks of these solar occurrences happen about every 11 years. The last peak of the solar cycle was in 2013, although scientists agree that that solar peak was weak compared to past ones.
People have been tracking the cycle of the sun’s activity for centuries now. Today, researchers keep a close eye on the changes to the weather in space, since these can affect orbiting spacecraft. They can even affect things on Earth by shutting down communication infrastructure and power grids. But on the plus side, they also make the auroras more striking to the eye.
Polar Attraction and Particles
Why are they called the “northern lights,” and why don’t they appear equally all over the globe?
Radiation, debris, and magnetic waves from space constantly hit the Earth. This normal bombardment also has the possibility of seriously affecting life as we know it, which is why scientists monitor it closely.
For the most part, the Earth’s magnetic field does a good job of protecting us, though. It deflects the particles and rays from the sun and from space that could harm us if they reached the Earth’s surface.
When the particles come from the sun, they have 93 million miles to travel before they start to reach our planet. Before they can get to the surface, the magnetic fields draw them toward the south and north poles. There, the particles make their way through the planet’s magnetic shield and come into contact with atoms and molecules of nitrogen, oxygen, and more elements.
It’s this contact that creates the beautiful northern lights we see in the night sky. However, they’re not always northern. The south pole draws particles just as much as the north pole does. In the northern hemisphere, the lights are called aurora borealis.
In the south, they’re known as aurora australis.
What Creates the Aurora’s Colours?
The colours you most often see in an aurora include green, blue, violet, pink, yellow, and less commonly, white or orange.
The shades of yellow and green come from the sun’s particles colliding with oxygen. Colours like red, violet, and blue come from collisions with nitrogen.
The altitude also affects the colours that appear. Green and red colours tend to appear higher, while blues, purple, and violet appear lower. Different types of collisions result in different colours, too. Molecular nitrogen will create a purple light, while atomic nitrogen shows up as blue.
Sometimes, the lights appear as still bands of colour. But if the solar flares are strong enough, you’ll see the famed dancing curtains of lights, changing colour as they go.
Where to See the Northern Lights
The so-called “northern lights” are rarely seen from the southern hemisphere, where there’s less land mass to view them from. The best places to see these displays include northern Canada and Alaska, as well as Finland, Sweden, and Norway.
In years when the solar flares are especially active, you might be lucky enough to see an aurora further south.
However, you can still experience the beauty of the aurora without chasing them down! Contact me to learn how you can get a beautiful print of the aurora borealis for display in your home.