Rotational Stabilization of Magnetically Collimated Jets

TL;DR

This paper explores how the rotation of accretion disks influences the stability of magnetically collimated astrophysical jets, demonstrating that higher rotation rates can suppress kink instabilities through Coriolis effects.

Contribution

It combines nonlinear MHD simulations with linear eigenmode analysis to show that disk rotation stabilizes jets against kink instabilities by distorting eigenmodes.

Findings

Jet stability increases with higher disk rotation rates.

Kink mode growth rate decreases as disk rotation speed increases.

Coriolis force plays a key role in stabilizing the jet.

Abstract

We investigate the launching and stability of extragalactic jets through nonlinear magnetohydrodynamic (MHD) simulation and linear eigenmode analysis. In the simulations of jet evolution, a small-scale equilibrium magnetic arcade is twisted by a differentially rotating accretion disk. These simulations produce a collimated outflow which is unstable to the current driven m=1 kink mode for low rotational velocities of the accretion disk relative to the Alfven speed of the coronal plasma. The growth rate of the kink mode in the jet is shown to be inversely related to the rotation rate of the disk, and the jet is stable for high rotation rates. Linear MHD calculations investigate the effect of rigid rotation on the kink mode in a cylindrical plasma. These calculations show that the Coriolis force distorts the m=1 kink eigenmode and stabilizes it at rotation frequencies such that the rotation period is longer than a few Alfven times.