In the X-wind model the magnetic field of a young Self-luminous object held together by its own self-gravity. Often refers to those objects which generate energy from nuclear reactions occurring at their cores, but may also be applied to stellar remnants such as neutron stars. interacts with the magnetic field of the circumstellar disk to produce a gap between the star and disk. As gas spirals inward through the disk, it divides at the inner disk edge (the X-region) into two streams. A high angular momentum stream is flung away along the rotating magnetic field lines of the disk (the X-wind); the low angular momentum stream falls onto the star and helps build its mass.
Image source: http://www.psrd.hawaii.edu/Dec01/Oisotopes.html.