Biggest solar storm in a decade creates spectacular aurorae over the UK
Aurorae can create many different patterns and colours during a display, but this can change dramatically within seconds. The colours are due to atoms and molecules in Earth's atmosphere de-exciting following a collision with a charged particle from the Sun. We find that different atoms give off different colours of the spectrum after they are excited. Oxygen at about 90 kms (60 miles) up gives off the familiar yellow-green colour, whilst Oxygen at higher altitudes (200 miles) gives the all red auroras. Ionised Nitrogen produces much of the blue light we see and neutral Nitrogen gives off the red-purple colour and leads to rippling at the edges.