Prompt radiation of a nuclear detonation in vacuum strips primary electrons from nuclei and radially drives them in an expanding sphere. The electrons are negatively charged and low mass while the nuclei are positively charged and high mass.
An idealized approximation of this, however rough, is a stationary positive spherical surface through which the negative spherical surface radially oscillates. Since there is no curl in the magnetic vector potential of the oscillating negative sphere, no photons can escape. Is there any energy loss mechanism in this idealized system?
If so, what is it?
If not, can a test charge outside of the maximum extent of the negative sphere sense any change in the electric field during an oscillation?