ABSTRACT. We present the first three-dimensional, full-star simulations of convection in a white dwarf preceding a Type Ia supernova, specifically the last few hours before ignition. For these long-time calculations, we use our low Mach number hydrodynamics code, MAESTRO, which we have further developed to treat spherical stars centered in a three-dimensional Cartesian geometry. The main change required is a procedure to map the one-dimensional radial base state to and from the Cartesian grid. Our models recover the dipole structure of the flow seen in previous calculations, but our long-time integration shows that the orientation of the dipole changes with time. Furthermore, we show the development of gravity waves in the outer, stable portion of the star. Finally, we evolve several calculations to the point of ignition and discuss the range of ignition radii.

Key words: convection; hydrodynamics; methods: numerical; nuclear reactions, nucleosynthesis, abundances; supernovae: general; white dwarfs

Print publication: Issue 1 (2009 October 10)
Received 2009 May 22, accepted for publication 2009 August 24
Published 2009 September 21