Twisted Pseudodisk and Asymmetric Mass Accretion on the Circumstellar Disk

TL;DR

This study uses 3D resistive MHD simulations to show how magnetic field distortion and misalignment lead to asymmetric, complex accretion flows onto circumstellar disks, causing variability in protostar growth.

Contribution

It demonstrates that complex, asymmetric accretion structures naturally develop without turbulence or external asymmetries, highlighting intrinsic magnetic and rotational effects.

Findings

Magnetic fields become significantly distorted around the disk.

Accretion occurs through narrow, channelized flows.

Mass accretion onto the protostar is variable over time.

Abstract

We model gas inflow patterns onto circumstellar disks and the evolution of the pseudodisk using three-dimensional resistive MHD simulations. Starting from a prestellar core without turbulence and with a misalignment between the initial magnetic field and rotation axis, the simulations are performed for $\sim10^5$ yr after protostar formation. After disk formation, the magnetic field around the disk becomes significantly distorted due to the disk rotational motion. Consequently, the structure of the pseudodisk also evolves into a complex morphology. As a result, both accretion onto the disk and outflow become asymmetric and anisotropic. Accretion to the disk occurs primarily through narrow-channel flows or streams. The time evolution of the infalling envelope leads to non-steady accretion onto the disk, which in turn causes variability in the mass accretion onto the central protostar. This study demonstrates that complex infalling envelope structures and channelized accretion flows onto the disk naturally arise even without assuming turbulence or external asymmetric inflows.