Influence of the magnetic field on the formation of protostellar disks

TL;DR

This study uses 2D MHD simulations to explore how initial magnetic field strength influences the structure, size, and outflows of collapsing protostellar clouds, revealing a hierarchical structure and magnetic effects on disk formation.

Contribution

It provides new insights into the impact of magnetic energy on protostellar disk size, outflow intensity, and the formation of dead zones during collapse.

Findings

Primary disk size increases with initial magnetic energy.

Magnetic braking transports angular momentum more effectively at higher magnetic energies.

Outflow intensity correlates with initial magnetic energy.

Abstract

We numerically model the collapse of magnetic rotating protostellar clouds with mass of 10 $M_{sun}$. The simulations are carried out with the help of 2D MHD code Enlil. The structure of the cloud at the isothermal stage of the collapse is investigated for the cases of weak, moderate, and strong initial magnetic field. Simulations reveal the universal hierarchical structure of collapsing protostellar clouds, consisting of flattened envelope with the qausi-magnetostatc disk inside and the first core in its center. The size of the primary disk increases with the initial magnetic energy of the cloud. The magnetic braking efficiently transports the angular momentum from the primary disk into the envelope in the case, when initial magnetic energy of the cloud is more than 20 % of its gravitational energy. Intensity of the outflows launched from the region near the boundary of the first core increases with initial magnetic energy. The `dead' zone with small ionization fraction, $x<10^{-11}$, forms inside the first hydrostatic core and at the base of the outflow. Ohmic dissipation and ambipolar diffusion determine conditions for further formation of the protostellar disk in this region.