MAGNETICALLY STRIPED RELATIVISTIC MAGNETOHYDRODYNAMIC WINDS - THE CRAB-NEBULA REVISITED

Previous relativistic pair plasma MHD wind models of the Crab Nebula indicate that the ratio of the wind's Poynting flux to particle kinetic energy flux (≡ σ) must be very small. However, many current theories of pulsar magnetospheres and pulsar observations suggest that the spin-down luminosity should be primarily electromagnetic in origin and outward transport. For an oblique rotator, the asymptotic wind magnetic field near the rotational equator should consist of stripes of alternating toroidal field. A simple model of an initially high-σ striped MHD wind is developed which describes the reconnection annihilation of the opposite polarity stripes as the wind flows radially outward. The initially dominant Poynting flux is converted into particle thermal and directed kinetic energy well within the inner standing shock which terminates the superfast wind. A very crude model for the latitudinal distribution of magnetic flux in the striped wind suggests that the low value of σ which is inferred from the Crab Nebula models can be achieved if the magnetic dipole is inclined by about 80° to the pulsar's rotation axis.