The Northern Lights is a spectacular and beautiful stella display resulting in curtains of light dancing across the night sky. The scientific explanation behind the aurora borealis (‘northern dawn’ in Latin) is almost as fascinating and awe-inspiring as the lights themselves.
Believe it or not, the Earth is constantly bombarded by highly charged particles blown around by solar winds. Few of these particles ever reach the atmosphere because they are deflected by the Earth’s magnetic field. But every so often, the gentle solar winds turn into geomagnetic storms. Solar flares and coronal mass ejections (CME) – explosions of solar material into interplanetary space – can send powerful waves of charged particles toward the Earth. As these cosmic electrons collide with the Earth’s magnetic field, they generate millions of amps of electric current that arc along the magnetic field towards the poles.
If the force of a geomagnetic storm is severe enough, particles will breach the magnetic field at the poles, creating what is essentially the world’s biggest neon sign. As the supercharged electrons pass through the atmosphere, they excite gas atoms like oxygen and nitrogen. The excited gasses emit different coloured lights depending on their altitude and the power of the surge. Low-altitude oxygen is responsible for the fluorescent green hues and high-altitude oxygen produces those brilliant crimson reds. Nitrogen flares up as shades of blue and purple. The celestial light show is visible at the South Pole as well, there it’s called the aurora australis.
The cold vacuum of space seems an unlikely place for a storm. But that’s exactly what happens when a solar flare explodes into the Sun’s upper atmosphere, instantly heating nearby gasses to millions of degrees. The extreme heat causes gas atoms to split into positively charged ions and negatively charged free electrons. This supercharged soup of ionised gas is called plasma. The Sun emits a constant stream of plasma in all directions at a speed of 500km/s (a million mph). But when the flow of plasma becomes a flood, the Earth is in for some bad space weather.
Geomagnetic storms cause more than the majestic northern lights. They can warp the Earth’s magnetic field so badly that satellites are knocked out of orbit and invading electrons overwhelm power grids. In 1989, 6 million people in Montreal, Quebec lost power for nine hours thanks to a particularly strong solar storm.
How to photograph the Northern Lights
To get the best displays of the northern lights possible, you should find a location within the auroral belt as well as avoiding any light pollution. A great proportion of your shooting will be between northwest and southeast directions in the sky, so you should position your camera and tripod with glaring light sources to your south.
If you have checked aurora forecast reports and have headed out to find a very weak aurora, don’t be too put off: there’s still an opportunity for you to image the northern lights. Weak activity is still fine for photography, particularly if you’re in a relatively northern position.
When it comes to kit, these days many imagers like to use DSLR cameras and ensure that the settings of their camera allow for long exposure and high ISO noise reduction. Being prepared means that you should also have your gear ready to go at a moment’s notice. If you’re unsure of how your camera’s settings work, it’s a good idea to test it beforehand. You should ensure that you have removed your camera’s lens filter and pre-focused your device on a distant point like a mountain just before it gets dark. As a general rule of thumb, setting a camera with an aperture of f/2 to f/2.8 or wider to an exposure time of three to 30 seconds with a sensitivity of ISO 800 to 1600, should get very good shots of the northern lights.
Your imaging checklist
Decide if you want to shoot in RAW or JPEG – beginners may prefer JPEG for now
Set your camera’s LCD brightness to low
Remove the filter from your lens – this will ensure that you don’t have ‘rings’ in your images
Test camera exposure
Ensure you have a sturdy tripod and good ballhead
Keep a spare set of batteries and flash cards in your pocket. Cold conditions can drain batteries very quickly and shooting in RAW format can take up a lot of space on your device
Get a lens hood to protect from frost and condensation
Finding the Northern Lights
With the help of websites and apps available for iOS and Android, it is possible – albeit very roughly – to predict if you’ll be treated to a display of the northern lights.
Available on: iOS/Android
Cost: £1.91 / $2.99
Available on: Android
Available on: Android
If you’re interested in the astronomy, the northern lights or astrophotography be sure to check these out…
Main image: NASA/Stephane Vetter (Nuits sacrees)