  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.
