Continuity equations for the bound electromagnetic field

Abstract

We continue to analyze the Poynting theorem for the bound (velocity-dependent) electromagnetic (EM) field, initiated in our earlier paper (A L Kholmetskii et al 2011 Phys. Scr. 83 055406), and show that the character of the flow of EM energy substantially depends on the question of whether a bound EM field delivers the work to moving charged particles, or not. The latter case corresponds to the situation where the system of charged particles uniformly moves in space (which implies the presence of some forces of non-EM origin, which counteract EM interaction), and the entire EM energy density rigidly propagates in space along with the given system of charges. In the general case of arbitrary motion of interacting charged particles, the flow of EM energy is guided by the interactional part of the Poynting vector. A transition between these limited cases is explored, and physical implications of the obtained results are discussed.