On Feb 22, 9:22*pm, William Mook wrote:
When a rocket punches through vapor it creates a ring of clouds.

When there is no other light source, but the rocket itself, you see
only part of the ring.

When the sun is shining you see the whole thing.

http://apod.nasa.gov/apod/image/0911/ares1_duncan.jpg

Here's another photo that shows that the number of shock waves and
resulting vapor patterns - can be arbitrarily complex

http://www.armscontrolwonk.com/2636/shocking-good-fun