It is called "the Glory of the Pilot". Brian captured this image from his plane last week. He says you get the shot by hanging out the plane's window with the camera in one hand and the plane in the other. However he managed it, we think it is an incredible and beautiful image.
A 'glory' is an optical phenomenon that resembles an iconic saint's haloabout the shadow of the observer's head. The effect is believed to happen due to classical wave tunneling, when light nearby the droplet tunnels through air inside the droplet and, in the case of glory, is emitted backwards due to resonance effects. Which is a fancy way of saying that the light enters the cloud, and is then bounced back from the cloud to the observer.
The glory can only be seen when the observer is directly between the sun and cloud of refracting water droplets. Which means you have to be pretty much above the cloud... Hence, it is commonly observed whilst airborne, with the glory surrounding the airplane's shadow on clouds (when it is called The Glory of the Pilot). Glories can also be seen from mountains and tall buildings, when there are clouds or fog below the level of the observer