Multi-D magnetohydrodynamic modelling of pulsar wind nebulae: recent progress and open questions

TL;DR

This paper reviews recent advances in relativistic MHD modeling of pulsar wind nebulae, focusing on particle acceleration, magnetic dissipation, and reconnection processes, highlighting progress and unresolved questions in understanding nebula dynamics.

Contribution

It provides a critical overview of recent 3D simulations and theoretical insights into particle acceleration and magnetic reconnection in pulsar wind nebulae.

Findings

Identification of particle acceleration sites via wisps motion

Insights into magnetic dissipation in high magnetization nebulae

Potential explanation for Crab nebula gamma-ray flares through tearing instability

Abstract

In the last decade, the relativistic magnetohydrodynamic (MHD) modelling of pulsar wind nebulae, and of the Crab nebula in particular, has been highly successful, with many of the observed dynamical and emission properties reproduced down to the finest detail. Here, we critically discuss the results of some of the most recent studies: namely the investigation of the origin of the radio emitting particles and the quest for the acceleration sites of particles of different energies along the termination shock, by using wisps motion as a diagnostic tool; the study of the magnetic dissipation process in high magnetization nebulae by means of new long-term three-dimensional simulations of the pulsar wind nebula evolution; the investigation of the relativistic tearing instability in thinning current sheets, leading to fast reconnection events that might be at the origin of the Crab nebula gamma-ray flares.