Acceleration and Dissipation in Relativistic Winds

Abstract

I argue that ideal MHD relativistic winds are always limited in practice to asymptotic 4-velocity $γ_\infty \approx σ_0^{1/3}$ and asymptotic magnetization $σ\sim σ_0^{2/3} \gg 1$, where $σ_0$ is the wind magnetization with respect to the rest energy density, evaluated at the light cylinder of the rotating, magnetized compact object that drives the flow. This suggests that the observed low value of he asymptotic $σ$ in the equatorial sectors of the winds driving Pulsar Wind Nebulae and the associated high values of the asymptotic 4-velocity are a consequence of magentic dissipation in the wind zone.