Spiked Aurora

One of the most interesting feature of shooting Aurora is the ever changing and almost random pattern they form. Usually the form some kind of an arch over the sky. The shape of it depends on how high it is in the sky. If it is near the horizon the arch shape will be clearly visible. The higher up in the sky the Aurora then it looks less like an arch (because you are under it). 
Photo © copyright by Örvar Atli Þorgeirsson.