Well known crop circle researcher and photographer Lucy Pringle has identified a witness to the spectacular anomalous formation of a crop glyph.
She tells the story at her website here:
http://tinyurl.com/yfgojjaIt was 13 years ago that the witness and a friend saw the famous Julia Set fractal glyph being formed near Stonehenge. Over a 20 minute period they watched a strange mist swirl a few feet off the ground, finally creating the pattern in the crop.
The woman witness wants to remain anonymous but Lucy has recorded her testimony on tape.
Lucy comments that this is one of the most amazing crop circle
stories ever to come to light.
She told me: "It puts the phenomenon on a truly credible and indisputable scientific footing"
Lucy claims the mist is the effect of, and not the cause of the formation.

Here's what she says on the mist:
"The mist would appear to be as a result of cool water vapour rising from the aquifer (underground spring) beneath and behaves in a manner similar to what happens in the lab when electrical discharges are created through water and different patterns emerge on the surface.
Mist forms a little distance from the triggering point, which would support what occurred in this case, M could see the circle growing.
It is when the hydrogen atoms re-combine that all this happens as it draws in ambient energy. This is where the excess energy appears from.
As for height, it would be no higher than the radius of the formation created and the mist cloud would grow as the formation grew - i.e. the mist is effect of and not the cause of the formation."
Source : Dave Haith, sur la liste UFO Updates