THE ELECTROMAGNETIC-FIELD OF ELEMENTARY TIME-DEPENDENT TOROIDAL SOURCES

The radiation field of toroidal-like time-dependent current configurat ions is investigated. The infinitesimal time-dependent configurations are found outside which the electromagnetic strengths disappear but th e potentials survive. For a number of time dependences, their finite r adiationless counterparts can be found. In these cases topologically n on-trivial (unremovable by a gauge transformation) electromagnetic pot entials exist outside sources. The well-defined rule obtained for cons tructing time-dependent infinitesimal sources suggests the existence o f finite non-trivial radiationless sources with an arbitrary time depe ndence. The latter can be used to carry out time-dependent Aharonov-Bo hm-like experiments and to transfer the information. Using the Neumann -Helmholtz parametrization of the current density we represent the tim e-dependent electromagnetic field in a form convenient for application s.