The Origin of the Magnetic Field and Relativistic Particles in the Crab Nebula

Abstract

The power from the Crab Pulsar NP 0531 probably emerges partly as 30 Hz waves and partly as a relativistic wind containing a toroidal magnetic field. A shock discontinuity is expected where the pressure of the relativistic outflow balances the pressure within the nebula. This shock would occur at a radius R_s which is about 10 per cent of the total nebular radius R_neb . The relativistic particles and the magnetic flux would accumulate in the region R_s < R < R_neb . The magnetic field in this region would build up to equipartition strength, even if this field embodied only a few per cent of the relativistic energy outflow from the pulsar. The 30 Hz waves would be absorbed at R ≃ R_s , their energy being transferred to relativistic electrons. The continuum from the bulk of the nebula would then be entirely synchrotron radiation. The relevance of this model to various observed features of the Crab Nebula is briefly explored.