Relativistic plasma diffusion: a possible source for neutron star magnetic fields

Plasma density gradient which is inherent to degenerate neutron star matter is shown to lead to large scale plasma diffusion and subsequent charge separation. The surface (internal) fields generated by the spinning separated charges are found to be dipolar with intensities of ≃ 10¹⁴ G (for the surface fields) very early in the life-time of a typical neutron star. The internal fields, on the other hand, are relatively much weaker. These fields, which in this case are also shown to be temperature dependent, decay as a result of neutrino and photon emissions. The decay law derived from equations of standard cooling calculations and the equation connecting the magnetic field and temperature is indicated to have two distinct modes, each corresponding to the two branches of a typical neutron star cooling curve. We have found that results derived from the decay law are consistent with observational findings. Based on the theory behind our new model, we have also argued to show that isolated millisecond and sub-millisecond pulsars might be very rare objects. This revised version was published online in July 2006 with corrections to the Cover Date.