Aurora borealis: what are the Northern lights, when are they visible and how to see them in the UK
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As the sun reaches the peak of its 11-year cycle at the end of 2024 or early 2025, and the nights get longer, people in the UK will be more likely to be able to marvel at the stunning sights of the Northern Lights.
The lights were visible again on November 5 leading to a spectacular display. But what causes them, and when will the next be visible? Here is what you need to know.
What is the aurora?
The lights we see dancing in the sky are due to activity on the surface of the sun. As solar storms on our star (the Sun) produce huge clouds of electrically charged particles, some of these particles travel millions of miles, and eventually collide with the Earth.
Some of those particles then become captured in the Earth's magnetic field, which accelerates towards the north and south poles and into the atmosphere.
“These particles then slam into atoms and molecules in the Earth’s atmosphere and essentially heat them up,” explains Royal Observatory astronomer Tom Kerss. “We call this physical process ‘excitation’, but it’s very much like heating a gas and making it glow.”
The curtains of light are caused by the lines of force in the Earth's magnetic field and the colours are created as different gases are being heated. The two main gases in the Earth's atmosphere are nitrogen and oxygen. The green we see in the aurora is characteristic of oxygen, while hints of purple, blue or pink are caused by nitrogen.
“We sometimes see a wonderful scarlet red colour, and this is caused by very high altitude oxygen interacting with solar particles,” adds Kerss. “This only occurs when the aurora is particularly energetic.”
How can you see the Northern lights in the UK?
There are a few tools which helps to track when aurora borealis will be visible in the UK. Lancaster University's Department of Physics has a website called AuroraWatch UK, which estimates the likelihood of an aurora being visible based on geomagnetic activity.
AuroraWatchUK is also an app that is available to download, where you can wait for an amber or a red alert to see the phenomenon. However, it is important to keep an eye out for the tracker as any alerts mean the phenomenon is happening now.
It is always recommended to find a darker location, where light pollution may not ruin your chances of seeing the sight. They're more likely to be seen in the northern areas of Scotland, England, Wales and Ireland. However, in the past, they have been spotted as far south as Kent and Cornwall.
It is worth noting the sky needs to be clear and on a cloudy night the display may still happen but unfortunately, you may not be able to see it. In the north the display is known as the aurora borealis. In the southern hemisphere it is called the Aurora Australis.