Intrinsic and extrinsic angular momentum flux in radiation from ultrarelativistic charge

Abstract The angular momentum of radiation from an arbitrarily moving relativistic charge is studied. A charge moving along a curved path can emit radiation with high orbital angular momentum. In the ultrarelativistic case a significant part of this angular momentum is the product of the radiation pressure by the instantaneous radius of the trajectory curvature. This is an ‘extrinsic’ part of the angular momentum of the radiation. The rest of the angular momentum which we denote as ‘intrinsic’ angular momentum can be associated with ‘twisted’ radiation. In this paper, we investigate the intrinsic and spin components of the canonical angular momentum and the angular momentum following from the symmetrized stress-energy tensor. Explicit expressions for the intrinsic and extrinsic components of the angular momentum of the radiation are obtained and studied.