Northern Lights, also known as Aurora Borealis, are one of the most captivating phenomena you can witness. These dazzling displays of colourful lights are caused by interactions between the Earth’s magnetic field and charged particles from the Sun.
Over the weekend, a rare sight of the Northern Lights was witnessed across all parts of the UK, as well as much of London.
The natural light show, which isn’t normally visible in southern England, was the result of the biggest solar storm for more than 20 years. But what is the process behind this phenomenon?
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The aurora can be seen near the poles of both the northern and southern hemisphere, but in the north, the display is known as the aurora borealis.
According to the Royal Observatory at Greenwich, the lights we see in the night sky are actually caused by activity on the surface of the Sun. Solar storms on the surface of the star release huge clouds of electrically charged particles.
These particles can travel millions of miles and some of them may end up colliding with the Earth. Most of these particles are deflected, but some are captured by the Earth’s magnetic field.
Astronomer Tom Kerss said: “These particles then slam into atoms and molecules in the Earth’s atmosphere and essentially heat them up. We call this physical process ‘excitation’, but it’s very much like heating a gas and making it glow.”
So what we see are atoms and molecules in our atmosphere colliding with particles from the Sun. As different gases emit different colours when heated, the same process occurs in the aurora.
The two main gases in the Earth’s atmosphere are nitrogen and oxygen, and these elements emit different colours during an aurora display. The green we see in the aurora is characteristic of oxygen, while shades of purple, blue or pink are due to nitrogen.
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