They are seen regularly on night flights across the North Atlantic. They can be amazingly spectacular- mostly green 'drawing curtain' rapidly moving shapes, with fringes of violet in them. I have never seen them from ground level- the many photographs you can find on the net are spectacular, and there are reports that they can be accompanied by a sizzling sound. Over the last couple of days, it has been expected that the Northern lights should be spectacular as there is unexpected and extremely powerful solar sunspot activity causing an outburst of the coronal mass ejection that causes them high in the Earth's atmosphere. I did not see any activity Saturday night. The south polar regions have them as well, but there's almost nobody down there to see them. In short, they are a wonderful, electrifying and atmospheric phenomenon well worth seeing if you have the interest and inclination.
http://www.space.com/spacewatch/aurora_cam.html