Disk-Magnetosphere Interaction and Outflows: Conical Winds and Axial Jets

TL;DR

This paper uses axisymmetric and 3D MHD simulations to study conical winds and axial jets originating from the disk-magnetosphere boundary of rotating magnetized stars, revealing their structure, origin, and dependence on star and disk parameters.

Contribution

It demonstrates the formation of conical outflows and axial jets in different star regimes, highlighting the conditions that produce these outflows and their symmetry despite magnetic misalignment.

Findings

Conical outflows carry 10-30% of disk mass and angular momentum.

Axial jets appear in the propeller regime with high velocities.

Outflows are symmetric even with magnetic dipole misalignment.

Abstract

We investigate outflows from the disk-magnetosphere boundary of rotating magnetized stars in cases where the magnetic field of a star is bunched into an X-type configuration using axisymmetric and full 3D MHD simulations. Such configuration appears if viscosity in the disk is larger than diffusivity, or if the accretion rate in the disk is enhanced. Conical outflows flow from the inner edge of the disk to a narrow shell with an opening angle 30-45 degrees. Outflows carry 0.1-0.3 of the disk mass and part of the disk's angular momentum outward. Conical outflows appear around stars of different periods, however in case of stars in the "propeller" regime, an additional - much faster component appears: an axial jet, where matter is accelerated up to very high velocities at small distances from the star by magnetic pressure force above the surface of the star. Exploratory 3D simulations show that conical outflows are symmetric about rotational axis of the disk even if magnetic dipole is significantly misaligned. Conical outflows and axial jets may appear in different types of young stars including Class I young stars, classical T Tauri stars, and EXors.