SOME REMARKABLE CHARGE-CURRENT CONFIGURATIONS

We investigate how different magnetization distributions interact with an external electromagnetic field. Strong selectivity to the time dep endence of the external electromagnetic field arises for particular ma gnetizations and suggests that it can be used for practical applicatio ns. We review the properties of the known charge-current radiationless configurations. The radiation field of toroidal-like time-dependent c urrent configurations is investigated. Infinitesimal time-dependent co nfigurations are found outside which the electromagnetic field strengt hs disappear but the potentials survive. For a number of time dependen ces, their finite radiationless counterparts can be found. In these ca ses topologically nontrivial (unremovable by a gauge transformation) e lectromagnetic potentials exist outside the sources. The well-defined rule obtained for constructing time-dependent infinitesimal sources su ggests the existence of finite nontrivial radiationless sources with a rather arbitrary time dependence. The latter can be used to carry out time-dependent Aharonov-Bohm-like experiments. Examples are given of nonstatic current configurations generating the static electric field and adequately described by the electric vector potential rather than by the scalar one. (C) 1998 American Institute of Physics.