RADIATION PRESSURE-DRIVEN MAGNETIC DISK WINDS IN BROAD ABSORPTION-LINE QUASI-STELLAR OBJECTS

We explore a model in which QSO broad absorption Lines (BALs) are form ed in a radiation pressure-driven wind emerging from a magnetized accr etion disk. The magnetic field threading the disk material is dragged by the flow and is compressed by the radiation pressure until it is dy namically important and strong enough to contribute to the confinement of the BAL clouds. We construct a simple self-similar model for such radiatively driven magnetized disk winds, in order to explore their pr operties. It is found that solutions exist for which the entire magnet ized flow is confined to a thin wedge over the surface of the disk. Fo r reasonable values of the mass-loss rate, a typical magnetic field st rength such that the magnetic pressure is comparable to the inferred g as pressure in BAL clouds, and a moderate amount of internal soft X-ra y absorption, we find that the opening angle of the how is approximate ly 0.1 rad, in good agreement with the observed covering factor of the broad absorption line region.