The colours of the Northern Lights

What are the Northern Lights?

Solar winds consist of a stream of plasma particles that are emitted from the sun. These can cause disturbances known as geomagnetic storms. When the solar wind surges, we see a coronal mass ejection. CMEs often happen alongside solar flares, when intense high-energy radiation bursts from the sun's surface.

During such events, energised particles enter the earth’s upper atmosphere. These react with the gas molecules found there, such as nitrogen and oxygen, and become excited. When they return to their original state, they give off light. This can take the form of different colours dependent on the type of gas involved. This is what we refer to as the Northern Lights.

What do the various colours signify?

The Northern Lights can appear as various colours. Though we perhaps associate them with greens or purples, they can also appear as red, pink or even yellow displays. Sometimes, we see a mix of colours at the same time, perhaps in stripes or bands across the sky. Colours can also combine in the sky, making pink, purple or yellow.

No two experiences are alike, which goes some way to explaining why many people aren’t satisfied with seeing the aurora just once – it can become quite addictive! Let’s look at the three main colours that you might experience during a Northern Lights hunt in Iceland’s Reykjanes peninsula.

• Green

This is the most common colour of the aurora borealis. This signifies the collision of the charged particles with oxygen molecules. When this occurs at lower altitudes – usually between 60 and 150 miles above the surface of the earth – the result is a green light, which can vary in tone from a blue-ish green to one with a yellow tinge.

Fun fact: our eyes can more easily see green Northern lights as this colour appears in the middle of our visual spectrum.

• Red

Oxygen particles can also be the cause of a red aurora, though this is considerably less common. This colour occurs when the reaction takes place at higher altitudes, for instance those more than 150 to 180 miles up. There’s a lower density of oxygen, so such sightings in the thinner atmosphere appear far less frequently. However as they can occur during strong solar activity, you might see this colour – albeit very occasionally – at relatively low latitudes.

• Pink, purple, violet or blue

When the aurora appears in shades of pink, purple, violet or blue, it’s because of the presence of nitrogen. This colour is typically associated with high solar activity. When the aurora shows up in this shade it is relatively unusual, created by higher energy protons colliding with nitrogen in our atmosphere. You’ll sometimes see a purple border beneath a green aurora where both oxygen and nitrogen are having an effect.

Can the aurora appear white?

Sometimes when you’re out looking for the Northern Lights, you see a white-ish band, curtain or ribbon that moves across the sky. Though you might be forgiven for thinking that this means the aurora can be white too, it’s actually a result of the way our eyes function. Our night vision can see brightness before it can see colour.

In comparison, our smartphones and cameras can pick out the colour much more easily. Sometimes, therefore, you might confirm a suspicion that the Northern Lights are dancing overhead by holding up your screen and viewing the sky through it rather than looking at it with the naked eye.

Are the colours of the aurora always vivid?

If the Northern Lights are really intense, it’s easier to see their colours. But if they’re not very strong, or you are viewing them in an area that’s impacted by light pollution such as within a built up area, then the colours can appear washed out or hard to see at all. That’s why it’s so important to find as dark a spot as possible when trying to observe the aurora borealis.

Digital photography means that it’s very straightforward to edit the images that we take. Manipulating colours and cropping the shots we take can be done in a matter of seconds on a smartphone. The result is that the pictures of the Northern Lights that we see on the internet and on our screens aren’t necessarily representative of what you’d see if you’d have been there yourself.

Manage your expectations

Does that mean you shouldn’t go on a Northern Lights hunt? No, of course not. If you do get the chance to see such a fickle natural phenomenon, it is a massive tick off your bucket list. Even a fleeting glimpse is really special and if the ribbons and curtains dance across the heavens for any length of time you’ll truly appreciate why they inspire such awe and wonder.

Seeing the aurora borealis is a magical moment, but you should nevertheless manage your expectations so that you have a realistic idea of the range and depth of colour you might see. And take a tip from us: make sure you have your camera or smartphone with you to be able to appreciate the full effect of what’s happening in the sky above you…