Modelling the Kinked Jet of the Crab Nebula

TL;DR

This study uses 3D relativistic MHD simulations to analyze the kinked structure and dynamics of the Crab Nebula's South-East jet, revealing how magnetic instabilities influence jet deflection and stability.

Contribution

It provides the first detailed 3D relativistic MHD models of the Crab Nebula jet, highlighting the effects of magnetic instabilities and flow parameters on jet behavior.

Findings

Jet deflection caused by kink instabilities observed.

Higher flow velocities and lower magnetic fields stabilize the jet.

Model results align with Chandra X-ray observations of jet direction changes.

Abstract

We investigate the dynamical propagation of the South-East jet from the Crab pulsar interacting with supernova ejecta by means of three-dimensional relativistic MHD numerical simulations with the PLUTO code. The initial jet structure is set up from the inner regions of the Crab Nebula. We study the evolution of hot, relativistic hollow outflows initially carrying a purely azimuthal magnetic field. Our jet models are characterized by different choices of the outflow magnetization ($\sigma$ parameter) and the bulk Lorentz factor ($\gamma_{j}$). We show that the jet is heavily affected by the growth of current-driven kink instabilities causing considerable deflection throughout its propagation length. This behavior is partially stabilized by the combined action of larger flow velocities and/or reduced magnetic field strengths. We find that our best jet models are characterized by relatively large values of $\sigma$ ($\gtrsim 1$) and small values of $\gamma_{j}\simeq 2$. Our results are in good agreement with the recent X-ray (\textit{Chandra}) data of the Crab Nebula South-East jet indicating that the jet changes direction of propagation on a time scale of the order of few years. The 3D models presented here may have important implications in the investigation of particle acceleration in relativistic outflows.