It is shown that the magnetic moment μ is a conserved quantity not only in MHD, but also in general electrodynamics under certain not very restrictive conditions. The propagation of magnetic moment from a regionDwith an evolving current system (e.g., due to dynamo action) is discussed for the two cases of vacuum and a conducting medium, respectively, surroundingD. In the case of vacuum, the MHD approximation no longer holds and the weak electromagnetic wave emitted fromDis important, as was pointed out by Sokoloff (1997). In the case of an unbounded conducting medium, the classical definition of μ is generalised and μ is shown to propagate diffusively, undisturbed by the newly generated magnetic field.