I just looked at three videos, and they all look as though this occurred at night. Where would the sunlight have been coming from? Atmospheric refraction?
http://gizmodo.com/5422574/giant-mysterious-spiral-takes-over-the-skies-of-norway
This is a link to a series of several photos. (It was linked in one of the earlier FR threads).
One person said it happened from 7:30 to 8:00 A.M. In the photos near the horizon you can see the sun rising in the background. The higher-up photos are very dark. I wish they had a time sequence of the photos. The blue plume in the sunlight photos is just a hazy plume (no spiral).
I’m still leaning towards the out-of-control rocket theory - but lots of flaws in that it would seem. Mainly the perfect spirals. But, the photo sequence does tend to support a rocket.