PULSAR STATISTICS WITH NONEXPONENTIAL MAGNETIC-FIELD DECAY

The evolution of neutron star magnetic fields plays a fundamental role in a wide variety of phenomena associated with pulsars, X-ray binaries, and gamma-ray bursters. It has been widely, but not unequivocally, assumed that neutron star magnetic fields decay exponentially. However, many of the proposed models for field decay suggest that the decay is related to the ohmic decay of crustal fields or electrical currents which, however, decay nonexponentially in general (Sang and Chanmugam). Using the calculated field decay histories, we examine pulsar statistics. We show that nonexponential field decay is consistent with the current understanding of pulsar statistics. Since the field decays nonexponentially and may retain a substantial fraction of its initial strength at ages ≥ 109 yr, it may provide a natural explanation for the millisecond pulsar magnetic fields.