Many times the aurora appears in the sky in as many as five or six bands. Depending on your geographic location in respect to the magnetic poles, the aurora appears in different perspectives.
The closer the viewer is to the Auroral Oval, the higher in the sky the aurora appears. When the aurora is directly above the viewer's head, it is referred to as a zenith view. When the auroral curtain is very active, the curtain form is harder to be distinguished by the viewer. This active curtain is called the corona.
The further away the viewer is from the corona, the more band-like the aurora appears. As the viewer moves closer to the corona from the farthest viewing point, the aurora seems to arc toward the horizon. This is known as perspective. Perspective results from the curvature of the earth. Because the viewer is hundreds of miles away from where the actual Auroral Oval is located, he can see more of the auroral curtain (and thus the arc form).
