Interaction of circling relativistic charges and interference in their radiation

The radiation emitted by two charges circling at opposite ends of a diameter at arbitrary uniform speed is considered, with special attention being paid to interference effects. The difference in the rate of radiation from the system and the sum of the powers emitted separately by each circling charge is shown to be equal to the work done by the particles on each other through their exact Liénard-Wiechert fields, in accordance with the Poynting theorem. Some peculiarities of the radiation at high and low speeds are noted and explained. © 1997 American Association of Physics Teachers.