The Science Behind Aurora Borealis: How Solar Wind and Earth’s Magnetic Field Create the Northern Lights

What causes the phenomenon Aurora borealis? – Ffion, almost 7 years old, Pembrokeshire, England.

I first saw the phenomenon Aurora borealis (northern lights) three years ago, while driving home one night. The light was so beautiful, I had to stop the car and get out to see it clearly, even though it was cold. While the northern lights may seem like magic, they can actually be explained by science – with a little help from the sun, birds and coke.

The energy that produces these northern lights comes from the sun. The sun creates something called the “solar wind”. This is different from the light we get from the sun which keeps us warm and helps us see during the day.

This solar wind moves away from the sun through space, carrying tiny particles called protons and electrons. Protons and electrons are the tiny building blocks that make up most of the things in the universe like plants, chocolate, me and you.

Imagine the smallest lego blocks you can find in your toy box that can be put together to make something bigger – that’s the protons and electrons (and also the neutrons) in the universe. These particles carry a lot of energy from the sun on their way through space.

solar wind

Sometimes the solar wind is strong and sometimes it is weak. We can only see the northern lights when the solar wind is strong.

When the solar wind reaches planet Earth, something very interesting happens: it hits Earth’s magnetic field. The magnetic field pushes the solar wind away and makes it revolve around the Earth.

It’s this magnetic field that makes compass needles point north, and it’s how birds know where to go when they migrate – it’s also why we have north and south poles.

The magnetic field interacts with the solar wind and guides protons and electrons towards Earth along the magnetic field away from the center of the planet and towards the north and south poles.

Because of this, we get north polar light and south polar light – also known as Aurora borealis and the southern dawn.

Why is the color of the aurora borealis green?

When the solar wind passes through the magnetic field and moves toward Earth, it enters the atmosphere. The atmosphere is like a huge blanket of gas surrounding our planet that contains many different particles that make up the air we breathe and help protect us from harmful radiation from the sun.

When protons and electrons from the solar wind hit particles in Earth’s atmosphere, they release energy – and this is what causes the northern lights.

Here’s the process: imagine you have a bottle of coke, and you shake it. This will put a lot of energy into the bottle and when you open it, this energy will be released in the form of fizzy bubbles.

In the same way, protons and electrons from the sun “shake up” particles in the atmosphere. Then, the particles release all that energy in the form of light (not bubbles).

Different types of particles in the atmosphere produce different colors after being shaken – oxygen produces red and green light and then nitrogen produces blue light. Our eyes see green best of all colors, so we see green the brightest when looking at the northern lights.

It’s easiest to see the northern lights in winter when it’s very dark at night, and also outside of cities and away from street lights. You’ll also see it more easily if you are farther north. Take a look at a good website This from Lancaster University in the UK – might be able to help you find it!

Demetrius Adyatma Pangestu from Bina Nusantara University translated this article from English