The angular momentum problem and magnetic braking during star formation: exact solutions for an aligned and a perpendicular rotator

The problems of fragmentation, angular momentum, and magnetic flux during star formation are reviewed briefly. Then the resolution of the angular momentum problem through magnetic braking is studied rigorously. A disk-like interstellar cloud of uniform density rhosub(cl) is given an initial angular velocity Ω0 about its axis of symmetry, which is aligned with an initially uniform, frozen-in magnetic field. Torsional Alfven wave transport angular momentum from the cloud to the external medium, which has a uniform density rhosub(ext). The angular velocity of the cloud (Ωsub(cl)) is determined analytically. A cylindrical cloud (or fragment) of uniform density is also considered. (Auth.)