Interaction of a magnetized pulsar wind with its surroundings. MHD simulations of Pulsar Wind Nebulae

TL;DR

This paper presents magnetohydrodynamical simulations of magnetized pulsar wind nebulae interacting with their surroundings, confirming elongation due to magnetic fields and modeling their expansion, with implications for understanding specific nebulae like 3C58.

Contribution

The study provides detailed MHD simulations of pulsar wind nebulae interacting with the environment, validating semi-analytical predictions and exploring the effects of magnetization on nebula morphology and expansion.

Findings

Nebulae are elongated by toroidal magnetic fields.

Expansion follows a standard power-law rate.

Magnetization weakly affects elongation.

Abstract

Magnetohydrodynamical simulations are presented of a magnetized pulsar wind interacting directly with the interstellar medium, or, in the case of a surrounding supernova remnant, with the associated freely expanding ejecta of the progenitor star. In both cases the simulations show that the pulsar wind nebula will be elongated due to the dynamical influence of the toroidal magnetic fields, which confirm predictions from a semi-analytical model presented by Begelman & Li. The simulations follow the expansion of the pulsar wind nebula when the latter is bounded by a strong shock and show that the expansion can be modeled with a standard power-law expansion rate. By performing different simulations with different magnetization parameters, I show that the latter weakly correlates with the elongation of the pulsar wind nebula. The results from the simulations are applied to determine the nature of the expansion rate of the pulsar wind nebula 3C58. It is shown that there is both observational and theoretical evidence which supports the scenario in which the pulsar wind nebula 3C58 has caught up with the reverse shock of the associated (but undetected) supernova remnant.