Most auroras occur between 90 and 130 km above sea level. The Northern and Southern Lights dance simultaneously and are almost mirror images of each other.
The way the aurora works is a lot like a neon sign, except that in the aurora, the conducting gas is in the upper layer of the atmosphere, instead of a glass tube, and the current travels along magnetic field lines instead of copper wires.
There has been almost no auroral activity for quite a long time this winter, and two times I went out in the cold, and got nothing. So here is an older post, actually, a re-post with a little different process.
The foreground was illuminated with a torch, very briefly. The purple color in the sky is light pollution from the city. It could not be seen by the eye, but the camera caught it.
ISO 1600 ; f/4 ; 30 sec ; @10mm
Taken on my older camera, a year ago.