Time-dependent accretion by magnetic young stellar objects as a launching mechanism for stellar jets

A time-dependent jet launching and collimating mechanism is presented. Initial results of numerical simulations of the interaction between an aligned dipole rotator and a conducting circumstellar accretion disk that is initially threaded by the dipole field show that differential rotation between the disk and the star leads to the rapid expansion of the magnetic loops that connect the star to the disk. The expansion of these magnetic loops above and below the disk produces a two-component outflow. A hot, well-collimated outflow is generated by the convergent flow of attached plasma toward the rotation axis, while a cool, slower outflow is produced on the disk side of the expanding loop. The expanding loop, which later forms a plasmoid, defines the boundary between the jetlike flow and the disk wind. Episodic magnetic reconnection above and below the disk releases the jet plasma from the system and allows the process to repeat, reinforcing the hot, well-collimated outflow.