Atmospheric
Optics
Water Aureole
~ Imaged by Brigitta Sipocz at Antofagasta, Chile. The shadow of Brigitta's camera and head is surrounded by a wavy aureole. Only your own shadow is so surrounded.
Images ©Brigitta Sipocz, shown with permission
When looking down in the direction of the sunlight the caustic sheets appear by perspective to converge to a point. These are the ‘rays’ of the water aureole.
The view of the caustic sheets is distorted as rays reaching the eye are again refracted by the waves.
Look for a water aureole where your shadow is directly opposite the sun. They need a very gentle wavy surface on water maybe 1m deep or more. The water must be slightly turbid so that sun rays passing through are visible.
The gentle waves refract sunlight to form downward going sheets of intense light. These are caustics – More about caustics here. The sheets are roughly parallel.
