Disks and winds in Young Solar-Type Stars: the Magnetic Connection

I discuss in this contribution the accretion and ejection processes occurring in solar-type young stars. Understanding these two important processes, and their link, is one of the major issues in star formation. The magnetic field is thought to play a central role in both extracting the angular momentum from the disk and directing the accretion flow onto the star. I will focus on the well studied T Tauri stars, optically-revealed pre-main sequence stars with ages 1-10 Myrs and mass ≃ 0.5 M_⊙. In the first part of this contribution, I present the current paradigm for magnetically channeled accretion, where the stellar magnetic field truncates the disk and directs the accretion flow and discuss recent observations, which indicate that this process is non-axisymmetric and time-dependent. I then turn to the study of the supersonic collimated jets observed in young stars. Magneto-hydrodynamic processes are the most likely driving mechanism. I present the main steady and non-steady outflow models, as well as constraints brought by recent high-resolution studies. I finally discuss the origin of time variability in jets.