On the time dependence of field in the near-field zone of a nonstationary multipole

The subject of consideration is the time dependence of the field in the near-field zone of an (acoustic or electric) dipole generating a nonmonochromatic signal smoothly varying with time. It is shown that this dependence is approximately the same at different points in the near-field zone; i.e., the smooth signal does not lag in time, as it might with regard to a finite velocity of wave propagation. The absence of delay is a result of interference between two identical but differently damped and delayed copies of one signal that are emitted from two monopoles constituting the dipole. The same is true for an arbitrary electroneutral (as a whole) set of nonstationary charges (in particular, for a nonstationary quadrupole, octupole, etc.). (c) 2005 Pleiades Publishing, Inc.