Two-flow magnetohydrodynamical jets around young stellar objects

TL;DR

This paper presents pioneering simulations of coupled stellar winds and disc-driven jets in young stellar objects, revealing how thermal and magnetic forces accelerate outflows and how stellar winds influence jet structure and mass ejection.

Contribution

First self-consistent simulation of non-ideal MHD stellar winds coupled with disc-driven jets, highlighting the roles of thermal and magnetic acceleration mechanisms.

Findings

Inner outflow accelerated by thermal pressure and Lorentz force

Resistive disc-driven jets mainly magneto-centrifugally accelerated

Dense stellar winds modify jet structure and increase mass ejection

Abstract

We present the first-ever simulations of non-ideal magnetohydrodynamical (MHD) stellar winds coupled with disc-driven jets where the resistive and viscous accretion disc is self-consistently described. The transmagnetosonic, collimated MHD outflows are investigated numerically using the VAC code. Our simulations show that the inner outflow is accelerated from the central object hot corona thanks to both the thermal pressure and the Lorentz force. In our framework, the thermal acceleration is sustained by the heating produced by the dissipated magnetic energy due to the turbulence. Conversely, the outflow launched from the resistive accretion disc is mainly accelerated by the magneto-centrifugal force. We also show that when a dense inner stellar wind occurs, the resulting disc-driven jet have a different structure, namely a magnetic structure where poloidal magnetic field lines are more inclined because of the pressure caused by the stellar wind. This modification leads to both an enhanced mass ejection rate in the disc-driven jet and a larger radial extension which is in better agreement with the observations besides being more consistent.