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 a n 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 o f the magnetic loops that connect the star to the disk. The expansion of these magnetic loops above and below the disk produces a two-compon ent outflow. A hot, well-collimated outflow is generated by the conver gent flow of attached plasma toward the rotation axis, while a cool, s lower outflow is produced on the disk side of the expanding loop. The expanding loop, which later forms a plasmoid, defines the boundary bet ween the jetlike flow and the disk wind. Episodic magnetic reconnectio n above and below the disk releases the jet plasma from the system and allows the process to repeat, reinforcing the hot, well-collimated ou tflow.