Mass-loading of pulsar winds

Abstract

The dynamics of relativistic magnetized mass-loaded outflows carrying the toroidal magnetic field is analysed in the context of pulsar wind nebulae (PWNs). Mass-loading is very efficient in slowing down super-ielativistic magnetized flows and weakening relativistic shocks. We suggest that the weakening of relativistic reverse shocks by mass-loading in PWNs is responsible for the low radiative efficiencies of the majority of the PWNs. Mass-loading may also result in a shock transition near the fast magnetosonic point; this is unlikely to happen in the majority of PWNs. The evolution of magnetized mass-loaded flows beyond the reverse shock is complicated: after the initial deceleration to the minimal velocity required to transport the magnetic flux, the mass-loaded flows have to accelerate. This formally precludes mass-loaded Sows carrying ordered toroidal magnetic field from reaching infinity. The final outcome of mass loading of magnetized winds remains uncertain and may depend on kinetic details of how mass loading occurs.