Magnetohydrodynamic Jets Andwinds

The theory of magnetically accelerated outtows and jets from accretion disks is reviewed at an introductory level, with special attention to problem areas like the launching conditions of the ow at the disk surface, stability of the magnetic eld, and collimation mechanisms. This text will appear in R. 1.1 Introduction: the case for magnetic acceleration Narrow, high speed outtows (jets) and less well collimated`bipolar' outtows are observed from very diierent cosmical objects, ranging from protostars in the solar neighborhood, to galactic X-ray binaries, to the nuclei of active galaxies. The magnetic acceleration mechanism for outtows from accretion disks has gained signiicant popularity as an explanation for each of these forms of outtow. The model can account for high speeds (for example, Lorentz factors of 10 or higher in AGN and galactic black hole binaries), high degrees of collimation, and large momentum uxes. Though other processes can also, to varying degrees, account for these properties (e.g. Blandford 1993), the magnetic model combines them in a natural way. While some processes are very diierent in protostellar disks and the AGN or X-ray binary disks, in particular those that produce the observed radiation, the physics of the magnetic acceleration model is to a large degree independent of these. Progress made by development of the model for explaining 1