Although most of the plasma of the solar wind is diverted around the magnetosphere, geomagnetic storms can produce energetic particles inside the magnetosphere. When the particles reach the top of the atmosphere, they soon run into one of the molecules in the air. The collision stops the incoming particle and makes the air molecule light up. (The same system is used on a much smaller scale in a TV set - a beam of electrons from the back of the tube hits phosphor on the inside of the screen and makes it light up.) The light given off in the top of the atmosphere is visible from the ground if it is dark enough - the lights are known as the aurora borealis (northern lights) in the northern hemisphere, and the aurora australis in the southern hemisphere.

We offer a free Aurora Alert email service to warn you whenever aurora are likely to be seen across Britain. These alerts can be forwarded to your phone as a text message, so you will know when to look out for aurora wherever you are.