Related papers: The Outflow-Disc Interaction in Young Stellar Obje…
We study mass accretion and ejection in the vicinity of massive star forming cores using high-resolution (5 au) 3D AMR numerical simulations. We investigate the mechanisms at the origin of outflows and characterise the properties of the…
Young low-mass stars are characterized by ejection of collimated outflows and by circumstellar disks which they interact with through accretion of mass. The accretion builds up the star to its final mass and is also believed to power the…
According to the magnetospheric accretion scenario, young low-mass stars are surrounded by circumstellar disks which they interact with through accretion of mass. The accretion builds up the star to its final mass and is also believed to…
Recent observations have suggested that circumstellar disks may commonly form around young stellar objects. Although the formation of circumstellar disks can be a natural result of the conservation of angular momentum in the parent cloud,…
There is a growing number of observational indicators for the presence of bipolar outflows in massive, young stellar objects that are still accreting mass as part of their formation process. In particular, there is evidence that the…
This article represents a short review of the variability characteristics of young stellar objects. Variability is a key property of young stars. Two major origins may be distinguished: a scaled-up version of the magnetic activity seen on…
The formation and evolution of a circumstellar disk in magnetized cloud cores is investigated from prestellar core stage until sim 10^4 yr after protostar formation. In the circumstellar disk, fragmentation first occurs due to gravitational…
The origin of disks surrounding young stars has direct implications for our understanding of the formation of planetary systems. In the interstellar clouds from which star form, angular momentum is regulated by magnetic fields, preventing…
The role of outflows in the formation of stars and the protostellar disks that generate them is a central question in astrophysics. Outflows are associated with star formation across the entire stellar mass spectrum. In this review, we…
The interaction between a protostellar magnetosphere and a surrounding dynamo-active accretion disc is investigated using an axisymmetric mean-field model. In all models investigated, the dynamo-generated magnetic field in the disc arranges…
Many types of stars have strong magnetic fields that can dynamically influence the flow of circumstellar matter. In stars with accretion disks, the stellar magnetic field can truncate the inner disk and determine the paths that matter can…
In the current paradigm of star formation magnetic fields play a very central role. Indeed, they probably help or even channel the initial gravitational collapse of the parent molecular cloud. But their most spectacular effect is certainly…
This summary talk aims at highlighting some of the remaining open issues regarding the physics of the magnetospheric accretion/ejection process in young stellar objects (YSOs). It lists a number of questions related to YSOs magnetic fields…
We present our current understanding of the formation and early evolution of protostars, protoplanetary disks, and the driving of outflows as dictated by the interplay of magnetic fields and partially ionized gas in molecular cloud cores.…
An investigation is made of disk accretion of matter onto a rotating star with an aligned dipole magnetic field. A new aspect of this work is that when the angular velocity of the star and disk differ substantially we argue that the $\bf B$…
Young stars and planetary systems form in molecular clouds. For classical T Tauri stars (CTTS, F-K type precursors) the accretion disk does not reach down to the central star, but it is truncated near the co-rotation radius. The inner edge…
Disk accretion onto a magnetized star occurs in a variety of astrophysical contexts, from young stars to X-ray pulsars. The magnetohydrodynamic interaction between the stellar field and the accreting matter can have a strong effect on the…
In star formation, magnetic fields act as a cosmic angular momentum extractor that increases mass accretion rates onto protostars and in the process, creates spectacular outflows. However, recently it has been argued that this magnetic…
Magnetic fields are believed to have a vital role in regulating and shaping the flow of material onto and away from protostars during their initial mass accretion phase. It is becoming increasingly accepted that bipolar outflows are…
The birth of stars involves not only accretion but also, counter-intuitively, the expulsion of matter in the form of highly supersonic outflows. Although this phenomenon has been seen in young stars, a fundamental question is whether it…