Tidal truncation of accretion disks

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The prevalence and consequences of convection perpendicular to the plane of accretion disks have been discussed for several decades. Recent simulations combining convection and the magnetorotational instability have given fresh impetus to the debate, as the interplay of the two processes can enhance angular momentum transport, at least in the optically thick outburst stage of dwarf novae. In this thesis we seek to isolate and understand the most generic features of disk convection, and so undertake its study in both hydrodynamical and magnetohydrodynamical models. In the final part of this thesis (which is independent of the first two) we investigate the stress-pressure relationship in disks. The stresses accompanying MRI turbulence are related to the pressure in the disk, and have been shown to increase and decrease with the pressure. We examine the time lag associated with this dependence and discuss its implications for thermal instability.