Stability of Rotating Self-Gravitating Filaments:Stability of Rotating Self-Gravitating Filaments: Effects of Magnetic Field

TL;DR

This study performs a linear stability analysis of rotating, magnetized, self-gravitating filaments, revealing how magnetic fields and rotation influence their stability and collapse conditions, with implications for astrophysical filament stability.

Contribution

It provides an analytical framework for understanding the stability of rotating, magnetized filaments, extending previous work by including magnetic effects and rotation.

Findings

Magnetic fields reduce growth rates of perturbations, especially with axial magnetic fields.

Weak magnetic fields can significantly influence filament stability when rotation is slow.

Faster rotation enhances filament stability under magnetic influence.

Abstract

We have performed systemmatic local linear stability analysis on a radially stratified infinite self-gravitating cylinder of rotating plasma under the influence of magnetic field. In order to render the system analytically tractable, we have focussed solely on the axisymmetric modes of perturbations. Using cylindrical coordinate system, we have derived the critical linear mass density of a non-rotating filament required for gravitational collapse to ensue in the presence of azimuthal magnetic field. Moreover, for such filaments threaded by axial magnetic field, we show that the growth rates of the modes having non-zero radial wavenumber are reduced more strongly by the magnetic field than that of the modes having zero radial wavenumber. More importantly, our study contributes to the understanding of the stability property of rotating astrophysical filaments that are more often than not influenced by magnetic fields. In addition to complementing many relevant numerical studies reported the literature, our results on filaments under the influence of magnetic field generalize some of the very recent analytical works (e.g.,~\citet{jog2014}, etc.). For example, here we prove that even a weak magnetic field can play a dominant role in determining stability of the filament when the rotation timescale is larger than the free fall timescale. A filamentary structure with faster rotation is, however, comparatively more stable for the same magnetic field. The results reported herein, due to strong locality assumption, are strictly valid for the modes for which one can ignore the radial variations in the density and the magnetic field profiles.