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What are the Northern Lights?


The Aurora Borealis, or the Northern Lights have been illuminating the skies across the UK - from Orkney to Jersey. But what are they and why do they happen?

It is, in fact, all down to our relationship with the Sun.

How the Aurora Borealis occur

image copyrightSPL
  1. The Northern Lights are caused by the interaction of the solar wind - a stream of charged particles escaping the Sun - and our planet's magnetic field and atmosphere.
  2. As the solar wind approaches, it distorts the Earth's magnetic field and allows some charged particles from the Sun to enter the Earth's atmosphere at the magnetic north pole and the magnetic south pole. Then, as these charged particles "excite" gases in our atmosphere, they make make them glow - just like gas in a fluorescent tube.
  3. The solar wind can cause the Earth's magnetic field lines to disconnect from our planet. When these field lines "snap back" into position, charged particles from the solar wind are again pushed into the Earth's atmosphere, causing aurora. The more magnetic field lines that disconnect and snap back, the further south the Northern Lights can be seen.

Where could they be seen?

image copyrightOwen Humphreys /PA
image captionThe northern lights visible over St Mary's lighthouse, Whitley Bay, North Tyneside on 28 February

A particularly large and fast eruption on the Sun's surface on 25 February meant the Aurora could be seen further south than usual a few days later.

"When the sun has a major geomagnetic event, the flux of particles is so high that they can penetrate the Earth's atmosphere at lower latitudes, which is why in England it is only after these storms that we can see the lights," says the University of Lancaster's Professor Mike Kosch.

Maps from the US National Oceanic and Atmospheric Administration (NOAA) Space Weather Prediction Center show how far the Northern Lights were expected to be seen overnight on Thursday.

Aurora forecast for 27 February

image copyrightNOAA

Image courtesy of NOAA

But in fact, people reported seeing the lights much further south than predicted - including Gloucestershire, Essex, Norfolk and Jersey.

To increase the chance of seeing the Aurora Borealis, scientists advise viewers to sign up to an alert service and head outside at "magnetic midnight" - between 8pm and 12am in the UK - to find a dark place with no light pollution.

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