THE NONEXPONENTIAL EVOLUTION OF PULSAR MAGNETIC-FIELDS

We have carried out simulations of the evolution of the pulsars on the assumption that they evolve by emitting magnetic dipole radiation and have magnetic fields decaying according to the power law with index of -1/4. We have also done simulations on the assumption that the pulsars retain constant magnetic fields. We use the Monte Carlo techniques to generate sample pulsars of particular distributions of initial periods, period derivatives, magnetic dipole moments, lumimosities, and Galactic positions. The period-dependent beaming fraction of pulsars is considered in our simulation. Known selection effects which affect the actual observation are taken into account as accurately as possible. Then we have searched best fits by comparing the result of the simulation with the observed data of the pulsars. We conclude that the constant magnetic field model can account for the observed data comparatively well; the power-law decay model with index of -1/4 does considerably less satisfactorily.