On the Linear Stability of Sheared and Magnetized Jets Without Current Sheets - Non-Relativistic Case

TL;DR

This paper investigates how magnetic field structures and velocity shear influence the linear stability of non-relativistic, magnetized jets without current sheets, revealing that shear and magnetic fields together significantly enhance jet stability.

Contribution

It extends previous work by including jet shear effects and realistic magnetic structures, providing new insights into jet stability and a novel visualization method.

Findings

Shear stabilizes fundamental pinch modes at various wavelengths.

Shear strongly stabilizes short-wavelength kink modes.

Magnetic fields combined with shear enhance jet stability more than shear alone.

Abstract

In a prior paper (Kim et al. 2015) we considered the linear stability of magnetized jets that carry no net electric current and do not have current sheets. In this paper, in addition to physically well-motivated magnetic field structures, we also include the effects of jet shear. The jets we study have finite thermal pressure in addition to having realistic magnetic field structures and velocity shear. We find that shear has a strongly stabilizing effect on various modes of jet instability. Increasing shear stabilizes the fundamental pinch modes at long wavelengths and short wavelengths. Increasing shear also stabilizes the first reflection pinch modes at short wavelengths. Increasing shear has only a very modest stabilizing effect on the fundamental kink modes at long wavelengths; however, increasing shear does have a strong stabilizing effect on the fundamental kink modes at short wavelengths. The first reflection kink modes are strongly stabilized by increasing shear at shorter wavelengths. Overall, we find that the combined effect of magnetic field and shear stabilizes jets more than shear alone. In addition to the results from a formal linear stability analysis, we present a novel way of visualizing and understanding jet stability. This gives us a deeper understanding of the enhanced stability of sheared, magnetized jets. We also emphasize the value of our numerical approach in understanding the linear stability of jets with realistic structure.