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Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE, Physics, Plasma Physics, physics.plasm-ph
Abstract:
The energy lost by a rotation-powered pulsar is carried by a relativistic
flow containing a mixture of electromagnetic fields and particles. In the inner
regions, this is thought to be a magnetically dominated, cold,
electron-positron wind that is well described by the MHD equations. However,
beyond a critical radius r_{cr}, the same particle, energy and momentum fluxes
can be transported by a strong, transverse electromagnetic wave with
superluminal phase speed. We analyze the nonlinear dispersion relation of these
waves for linear and circular polarization, and find the dependence of r_{cr}
on the mass-loading, magnetization and luminosity of the flow, as well as on
the net magnetic flux. We show that, for most isolated pulsars, the wind lies
well outside r_{cr}, and speculate that superluminal modes play an important
role in the dissipation of electromagnetic energy into nonthermal particles at
the termination shock.
