Polytropic models of filamentary interstellar clouds -II. Helical magnetic fields

Abstract

We study the properties of magnetised cylindrical polytropes as models for interstellar filamentary clouds, extending the analysis presented in a companion paper (Toci & Galli 2014a). We formulate the general problem of magnetostatic equilibrium in the presence of a helical magnetic field, with the aim of determining the degree of support or compression resulting from the magnetisation of the cloud. We derive scale-free solutions appropriate to describe the properties of the envelopes of filaments at radii larger than the flat-density region. In these solutions, the polytropic exponent determines the radial profiles of the density and the magnetic field. The latter decreases with radius less steeply than the density, and field lines are helices twisted over cylindrical surfaces. A soft equation of state supports magnetic configurations that preferentially compress and confine the filament, whereas in the isothermal limit the field provides support. For each value of the polytropic exponent, the Lorentz force is directed outward or inward depending on whether the pitch angle is below or above some critical value which is a function of the polytropic exponent only.

arXiv comment8 pages, 1 figure. Accepted for publication in MNRAS

References in corpus (10)

• Characterizing interstellar filaments with Herschel in IC5146
• Herschel view of the Taurus B211/3 filament and striations: Evidence of filamentary growth?
• Helical Fields and Filamentary Molecular Clouds
• From Filamentary Networks to Dense Cores in Molecular Clouds: Toward a New Paradigm for Star Formation
• The Link between Magnetic Fields and Filamentary Clouds: Bimodal Cloud Orientations in the Gould Belt
• Near-Infrared Imaging Polarimetry Toward Serpens South: Revealing the Importance of the Magnetic Field
• Magnetohydrostatic Equilibrium Structure and Mass of Filamentary Isothermal Cloud Threaded by Lateral Magnetic Field
• Magnetic Fields in Star-Forming Molecular Clouds III. Submillimeter Polarimetry of Intermediate Mass Cores and Filaments in Orion B
• Polytropic models of filamentary interstellar clouds - I. Structure and stability
• Scale-free Equilibria of Magnetized Polytropic Clouds

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• Star-forming filament models
• Magnetic tension and instabilities in the Orion A integral shaped filament
• Is there a left-handed magnetic field in the solar neighborhood? Exploring helical magnetic fields in the interstellar medium through dust polarization power spectra
• Fast deuterium fractionation in magnetized and turbulent filaments
• Magnetohydrostatic Equilibrium Structure and Mass of Polytropic Filamentary Cloud Threaded by Lateral Magnetic Field
• Dynamical origin of non-thermal states in galactic filaments
• The origin of a universal filament width in molecular clouds
• Fragmentation of Filamentary Cloud Permeated by Perpendicular Magnetic Field II. Dependence on the Initial Density Profile
• Non-ideal magnetohydrodynamics of self-gravitating filaments
• Unveiling the role of magnetic fields in an accreting filament onto a young protocluster