Radiative pulsar magnetospheres: oblique rotators

TL;DR

This paper models pulsar magnetospheres with radiation reaction effects, revealing how pair multiplicity influences energy conversion and radiation, and showing that magnetic topology remains largely unaffected.

Contribution

It introduces a numerical approach to simulate radiative pulsar magnetospheres with variable pair multiplicity, connecting particle dynamics and radiation self-consistently.

Findings

Higher pair multiplicity reduces spin-down energy conversion into radiation.

Low multiplicity leads to significant energy loss via particle acceleration.

Magnetic topology remains largely unchanged across models.

Abstract

Pulsar magnetospheres are filled with relativistic pairs copiously emitting photons detected from the radio wavelengths up to high and very high energies, in the GeV and sometimes in the TeV range. Efficient particle acceleration converts the stellar rotational kinetic energy into radio, X-ray and gamma-ray photons. Force-free magnetospheres, being dissipationless, cannot operate this conversion. Some non ideal plasma effects must set in within the magnetosphere. In this paper, we compute numerical solutions of pulsar radiative magnetospheres in the radiation reaction limit, where radiation fully balances single particle acceleration. Using an appropriate Ohm's law, the dissipation is only controlled by the pair multiplicity factor~$\kappa$. Moreover we allow for either a minimal radiative region where dissipation is added only where required or for a force-free inside radiative outside model. This approach naturally and self-consistently connects the particle dynamics to its radiation field in the ultra-relativistic regime. Our solutions tend to the force-free limit for moderately large multiplicities, $\kappa \gg 1$, decreasing the spin-down energy conversion into radiation. Nevertheless, for sufficiently low multiplicity $\kappa \lesssim1$, a significant fraction of the spin-down energy flows into radiation via particle acceleration. The work done by the electromagnetic field on the plasma mainly occurs in the current sheet of the striped wind, right outside the light-cylinder. Nevertheless the impact on the magnetic topology is negligible whatever the model. Therefore the associated sky maps and light-curves are only weakly impacted as shown.