Transient electromagnetic singularities in random three-dimensional optical fields

We show that on all generic circular or elliptical paths in a random three-dimensional electromagnetic field, the electric and magnetic field vectors generate a cylinder throughout most of the optical cycle. At some point in the cycle, however, this cylinder transforms into a twisted ribbon with two sequential 180^◦ twists. This ribbon exists for a short time and then unwinds, regenerating the cylinder. We discuss how and why these structures form and what determines their lifetimes.