Electromagnetic Waves Generated by Null Cosmic Strings Passing Pulsars

Null cosmic strings disturb electromagnetic (EM) fields of charged sources and sources with magnetic moments. As has been recently shown by the authors, these perturbations result in a self-force acting on the sources and create EM waves outgoing from the sources. We develop an analytic approximation for asymptotic of the EM waves at the future null infinity and calculate radiation fluxes for sources of the both types. For magnetic-dipole-like sources the radiation flux depends on orientation of the magnetic moment with respect to the string. Estimates show that the peak power of the radiation can be quite large for null strings moving near pulsars and considerably large in case of magnetars. The string generated variations of the luminosities of the stars can be used as a potential experimental signature of null cosmic strings.
Comment: 25 pages, 5 figures, the version to be published, where the title is slightly changed and some equations are corrected