The magnetic field of pulsars and the gravito-magnetic theory

Abstract

Many authors have considered a gravitational origin of the magnetic field of celestial bodies. Especially, the so-called Wilson-Blackett formula has been investigated, both theoretically and observationally. It appeared possible to deduce this formula from general relativity, e. g., by application of a special interpretation of gravito-magnetic theory. More consequences of the latter theory for pulsars will be considered in this work. As an example, the standard quadrupolar charge density for pulsars can be deduced from the gravito-magnetic theory. Moreover, a new magnetic dipole moment from electromagnetic origin is found, generated in the basic magnetic field from gravito-magnetic origin. In general, for thirteen accreting, slowly rotating, binary pulsars the agreement between the observed magnetic field and the gravito-magnetic prediction is better than between the observed value and the value from the standard magnetic dipole radiation model. At present, an analogous comparison for five isolated pulsars appears to be difficult. For a sample of 100 pulsars the averaged (gravito-)magnetic field, extracted from the magnetic dipole spin-down model, is in fair agreement with the gravito-magnetic prediction. Unfortunately, the (gravito-)magnetic field has not yet directly been measured. Finally, it is found that the first and second order braking indices only depend on the magnetic field from electromagnetic origin.