Published in "Astrophysical Jets", eds. D. Burgarella, M. Livio and C. P. O'Dea, 1993

ACCELERATION AND COLLIMATION MECHANISMS IN JETS

Roger Blandford

130-33 Caltech, Pasadena, CA 91125, USA

Abstract. Acceleration and collimation mechanisms for jets and bipolar outflows associated with active galactic nuclei, young stellar objects, X-ray binaries and perhaps cataclysmic variables are briefly described. The case for magnetic collimation by magnetic field attached to orbiting accretion disks is developed. It is argued that good collimation is not accomplished too close to the source of the power but is established over several decades of disk radius. Some critical observations and theoretical calculations are suggested.

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