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E. A. Raley, S. W. Bruenn (Florida Atlantic University)
We have performed an analysis of fluid instabilities below the neutrinospheres of the collapsed cores of supernova progenitors using a methodology introduced by Bruenn and Dineva (Bruenn, S. W. and Dineva, T. S. 1996, ApJ, 458:L71-L74). In an extensive survey we found that the rate of lepton diffusion always exceeds the rate of thermal diffusion and as a result we do not anywhere see the neutron finger instability as described by the Livermore group (e.g. Wilson, J. R. and Mayle, R. W. 1993, Physics Reports 227:97-111). A new instability, lepto-entropy fingers, extending from a radius of 10-15 km out to the vicinity of the neutrinosphere, driven by the cross-response functions (i.e. the dependence of lepton transport on entropy perturbations and vice versa) was discovered. This instability has a maximum growth rate of the order of 100 s-1 with a scale of approximately 1/20 the distance of a perturbed fluid element from the core center (Bruenn, S. W., Raley, E. A., and Mezzacappa, A. to be submitted to the ApJ). This instability has probably already been seen in some multi-dimensional core collapse calculations.
Using two dimensional hydrodynamics with radial ray multigroup flux-limited neutrino transport we have simulated doubly diffusive instabilities below the neutrinosphere.
This work was partially funded by a grant from the DOE Office of Science, Scientific Discovery through Advanced Computing Program.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.