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Analytic and numerical work by several research groups over the last five years have shown that one-armed spiral instabilities (e.g. SLING) may play a crucial role in the evolution of protostars and protostellar disks. One-armed spirals have been shown to be effective at transporting angular momentum and mass and producing modest fragmentation.
We have recently conducted a numerical survey of global nonaxisymmetric instabilities in self-gravitating, rapidly rotating protostar models (Pickett et al. 1995, ApJ., submitted ). One interesting result is that the protostar models which correspond to equilibrium objects formed from the dynamical collapse of centrally condensed molecular clouds are quite unstable to one-armed spiral disturbances. These one-armed instabilities occur under conditions not anticipated by the work of others. Although significant mass and angular momentum transport occurs, the protostar does not fragment.
This poster presents a detailed investigation of the dramatic one-armed mode detected in Pickett et al. (1995). We use a variety of initial conditions and a second-order 3D hydrodynamics code to probe the nature of the instability in three dimensions. The relevance of this work to the formation of binaries and planetary systems will be discussed.
This work is supported by NASA grant NAGW-3399.
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