  We report the results of a series of three-dimensional (3-D) simulations of
the deflagration phase of the gravitationally confined detonation mechanism for
Type Ia supernovae. In this mechanism, ignition occurs at one or several
off-center points, resulting in a burning bubble of hot ash that rises rapidly,
breaks through the surface of the star, and collides at a point opposite
breakout on the stellar surface. We find that detonation conditions are
robustly reached in our 3-D simulations for a range of initial conditions and
resolutions. Detonation conditions are achieved as the result of an
inwardly-directed jet that is produced by the compression of unburnt surface
material when the surface flow collides with itself. A high-velocity
outwardly-directed jet is also produced. The initial conditions explored in
this paper lead to conditions at detonation that can be expected to produce
large amounts of $^{56}$Ni and small amounts of intermediate mass elements.
These particular simulations are therefore relevant only to high luminosity
Type Ia supernovae. Recent observations of Type Ia supernovae imply a
compositional structure that is qualitatively consistent with that expected
from these simulations.

Astrophysics