This going to be hard to explain so bear with me:
This is a crescent shape rainbow right above us. There's a thin layer of clouds. I look towards the sun and there's a band of light in a full circle, parallel to the horizon but further up. There are two twin sun spotlights (looks just light the sun but dimmer in the clouds at a 90 degree angle from the sun on a north and south bearing. This is the only way I can explain it, scientific. Here's a handful of photographs of the rainbow.
The darker images are from reducing light exposure in the camera.
Dark Side of the Rainbow