Hourglass Magnetic Field of a Protostellar System

TL;DR

This paper develops a realistic magnetic field model for protostellar systems, capturing the hourglass shape with features like a strong radial field, off-center peak, and toroidal components, aiding interpretation of observations.

Contribution

It introduces an analytic model incorporating magnetic field dissipation and toroidal components during the protostellar phase, advancing beyond previous smooth radial profiles.

Findings

Model reproduces observed hourglass magnetic field patterns.

Highlights the role of magnetic dissipation and toroidal fields in protostellar collapse.

Provides a framework for interpreting magnetic observations in star-forming regions.

Abstract

An hourglass-shaped magnetic field pattern arises naturally from the gravitational collapse of a star-forming gas cloud. Most studies have focused on the prestellar collapse phase, when the structure has a smooth and monotonic radial profile. However, most observations target dense clouds that already contain a central protostar, and possibly a circumstellar disk. We utilize an analytic treatment of the magnetic field along with insights gained from simulations to develop a more realistic magnetic field model for the protostellar phase. Key elements of the model are a strong radial magnetic field in the region of rapid collapse, an off-center peak in the magnetic field strength (a consequence of magnetic field dissipation in the circumstellar disk), and a strong toroidal field that is generated in the region of rapid collapse and outflow generation. A model with a highly pinched and twisted magnetic field pattern in the inner collapse zone facilitates the interpretation of magnetic field patterns observed in protostellar clouds.