Abstract
ABSTRACT In this paper, we describe the results of three-dimensional relativistic magnetohydrodynamic simulations aimed at probing the role of regular magnetic field on the development of the instability that accompanies recollimation of relativistic jets. In particular, we studied the recollimation driven by the reconfinement of jets from active galactic nuclei (AGN) by the thermal pressure of galactic coronas. We find that a relatively weak azimuthal magnetic field can completely suppress the recollimation instability in such jets, with the critical magnetization parameter σcr < 0.01. We argue that the recollimation instability is a variant of the centrifugal instability (CFI) and show that our results are consistent with the predictions based on the study of magnetic CFI in rotating fluids. The results are discussed in the context of AGN jets in general and the nature of the Fanaroff–Riley morphological division of extragalactic radio sources in particular.
Highlights
Jets from black holes of active galactic nuclei and young stars exhibit remarkable ability to propagate over very large distances, up to 109 of their initial radius at the jet “engine” (e.g. Porth & Komissarov 2015)
Recollimation of astrophysical jets can lead to instability. This recollimation instability is powered by the centrifugal force emerging along the curved streamlines of recollimating jets and is a variant of the classic centrifugal instability of rotating fluids
We explored the role played by such regular magnetic in the development of the recollimation instability
Summary
Jets from black holes of active galactic nuclei and young stars exhibit remarkable ability to propagate over very large distances, up to 109 of their initial radius at the jet “engine” (e.g. Porth & Komissarov 2015). This is in contrast to the expectations based on the linear stability analysis of cylindrical jets and laboratory experiments. The efolding length scale for the fastest growing body modes of KHI is lKHI ≈ MsR j, where Ms is the Mach number based on the sound speed and R j is the initial jet radius Both expressions apply to both Newtonian and relativistic flows, provided one uses the relativistic definitions of the Mach numbers in the latter case
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