The Auroras are a natural phenomenon which have been described about as far back as Roman times. A story I heard growing up was about an emperor who was in battle and thought Rome was burning, so he rushed back home only to realise it was the sky; dancing with coloured light casting a reddish-orange glow over the city he so loved.
The word Aurora is Latin and means sunrise, but it is also the name of the Roman goddess of dawn. There are 2 kinds of auroras, the Borealis and the Australis. The Borealis is known as the Northern Lights and mainly appear as a green glow occasionally tinged red. The appearance of the Borealis is generally around the equinoxes, and look like curtains due to the magnetic field lines which arise within them due to the polarity of The Earth. The Australis appears in the Southern hemisphere around the poles, and is essentially the same as the Borealis.
Auroras are formed via ions released from the Sun. The Earth's magnetic field traps the ions and it is the collision between the Sun's ions and the Earth's atmospheric molecules which cause the release of energy which is visualised as light (the auroras). It is the Earth's magnetic field which causes the appearance of the rippling effect associated with The Lights.
Auroras come in a wide range of colours, and this is dependent upon altitude. Red only occurs at the highest altitudes, green is apparent at the lower altitudes and the blue colour is occasionally seen at the lower part of the lights (the bottom of the curtains).
Explorer Fact: Last week the Northern lights were visible in some of the Southern Counties of Britain (Norfolk, Essex, Suffolk and Kent).