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Observations reveal that the rotational velocities of young low mass stars differ significantly depending on whether or not they show accretion disk signatures. Slower rotational velocities are found for those stars apparently surrounded by accretion disks suggesting that the disk may play a fundamental role in regulating the angular velocity of the central star, countering the tendency of the star to spin up both from contraction toward the main sequence and from accretion of disk material of high specific angular momentum. This would imply that the initial angular momentum of a forming star is the angular momentum it carries when its accretion disk is dissipated.
An interaction between the stellar magnetosphere and the accretion disk is a viable way to regulate the stellar angular velocity. Observational evidence supporting the role of magnetospheres in controlling the accretion flow onto the star is presented. The role of the magnetosphere in driving energetic winds from low mass young stars with accretion disks is less clear, but models relying on a magnetocentrifugal drive for ejecting winds in accretion disk systems provide the most efficient means of powering the winds, and also ensure that the wind contributes to the vital role of carrying angular momentum out of the system.
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