Abstract. In this lecture the basic theory of accretion disks is introduced, with emphasis on aspects relevant for X-ray binaries and Cataclysmic Variables. Key words: neutron stars, black holes, Caraclysmic Variables, accretion: accretion disks

Abstract. In this lecture the basic theory of accretion disks is introduced, with emphasis on aspects relevant for X-ray binaries and Cataclysmic Variables. To appear in ‘The neutron star black hole connection ’ (NATO ASI Elounda 1999, eds. C. Kouveliotou and V. Connaughton).

Abstract. Magnetic fields likely play a fundamental intermediary role between gravity and radiation in many astrophysical rotators. They can, among other things, 1) induce and be amplified by turbulence, 2) energize coronae, 3) launch and collimate outflows in “spring ” or “fling ” mechanisms The first is widely recognized to be important for angular momentum transport, but can also produce intrinsic variability and vorticity growth. The second leads to the production of high energy flares, and also facilitates a test of general relativity from AGN observations. The third can operate from rotators with a large scale fields, though the origin of the requisite large scale fields is somewhat unresolved. I discuss these three points in more detail below, emphasizing some open questions.

of an advanced particle detector

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An ACCRETION DISK is a flat formation of gas and dust rotating about a central object and accreting matter inwards by transporting angular momentum outwards, so that the centrifugal support is gradually removed from the fluid parcels. There are three main classes of accretion disks: (i) disks

Accretion disks appear to be favourable places for dynamo action, because of their strong differential rotation. A simple estimate of the strength of an accretion disk dynamo indicates that it will be highly nonlinear. In spite of this, most studies hitherto have assumed a linear model

for accretion disks. I show that although accretion disk flux tubes are usually almost completely evacuated, they are nevertheless less buoyant than previous estimates have suggested. I also note that vertical magnetic flux tends to be ejected from the outer edge of accretion disks, so evidence for continued