Barnes, Graham

Contact Email: barnesg@hao.ucar.edu
Institute: High Altitude Observatory
National Center for Atmospheric Research
First Coauthor: Keith MacGregor
Institute: High Altitude Observatory
Subject Area: Star Formation, Very Young Stars, T-Tauri, H-H Objects
Waveband: Other (Please Specify Below)
Technique: Computational Astrophysics
Other: Waveband is not applicable
Presentation: Poster Display
Title: Angular Momentum Transfer Between a T Tauri Star and an Accretion Disk
Abstract: It has been suggested that the rotational evolution of a T Tauri star can be regulated by the transfer of angular momentum between it and a magnetically coupled, circumstellar accretion disk. In such a system, the magnetic torque exerted on the star depends on (among other things) the strength of the toroidal field at the surface of the star. In most kinematic models for the magnetic interaction between a star and a disk, it is assumed that the magnitude of the induced toroidal field is limited by dissipative processes in the disk. We present results from dynamical calculations which show that, while kinematical estimates for the toroidal field strength may be valid within the disk, its value at the stellar surface can be orders of magnitude larger, yielding a correspondingly greater torque on the star. Our calculations also indicate that the low-density, highly conducting magnetosphere that surrounds both the star and the disk plays an important role in mediating the star-disk interaction, in contrast to kinematic models in which it is typically ignored. A general feature of our solutions is a shearing boundary layer, located in the magnetosphere just above the surface of the disk, wherein a substantial toroidal field is generated. In dynamical equilibrium, magnetospheric current systems contribute to a significant enhancement of this field between the boundary layer and the stellar surface.