Electromagnetic radiation produces frame dragging

Abstract: It is shown that for a generic electrovacuum spacetime, electromagnetic radiation produces vorticity of worldlines of observers in a Bondi--Sachs frame. Such an effect (and the ensuing gyroscope precession with respect to the lattice) which is a reminiscence of generation of vorticity by gravitational radiation, may be linked to the nonvanishing of components of the Poynting and the super--Poynting vectors on the planes othogonal to the vorticity vector. The possible observational relevance of such an effect is commented.