It may be an artiface of the camera sensor -if digital — Sunlight reflecting from light surface of kiln up into the smoke....I guess I should have said reverse shadow effect.
or not.
I have had some odd stuff show up in photos of things in snow...
There would be some obvious heat effects going on when photographing a kiln ;) I was (am still) curious about the near vertical line in the upper right hand quadrant. What do you think could cause that?