A classical T Tauri star is a pre-main sequence star surrounded by an accretion disk. Magnetic fields are thought to play a crucial part in the angular momentum evolution of the star. They can directly transfer angular momentum between star and disk, and also drive outflows. Computer simulations show how an initially dipolar field interacts with the accretion disk.
The images show the density distribution, magnetic field lines (solid lines), and gas motion (velocity vectors) in the volume surrounding the star. The left margin of each image is the stellar rotation axis. The left picture shows the initial configuration, the right picture the state that has evolved after about 100 orbits of the inner boundary of the disk. The original dipole is wound up due to the different rotation rates of the footpoints of each field line. The resulting magnetocentrifugal force drives part of the gas outwards and the dipole is replaced with an open field line configuration.
by courtesy of Manfred Küker
last change 2002 July 8, R. Arlt