One of the most beautiful wonders of natures is happening in Finland, mostly the north but on some rare occasions they find their way to the south of Finland. I have already seen them in the north of Norway, when I was working there and I can tell you, they are amazing. Here in Finland I had the pleasure to see them once very faded in the night sky but the were to fair to take a picture. When you have never seen them, you should consider going to Lapland, because up north it is more likely to see them.
Northern lights or Aurora borealis appear, when the electrically loaded particles of the sun enter our earths atmosphere. The most common colors of the dancing lights is green and pink, but in the north mostly green. There are also Aurora australis which are located in the south and they are mostly pink.
But don't be discouraged when you don't see them, they still are a natural phenomenon which appear and disappear how they like. There have to be good conditions, like a clear sky and a good KP-index.
The pictures are from Norway, because the ones I saw here were just too fair.
