Rayleigh-Taylor Instabilities in Supernovae Explosions: Helium Mass Fraction

The following calculation shows the development and evolution of Rayleigh-Taylor instabilities which develop behind the supernova blast wave on a time scale of a few hours. The initial model was chosen to provide a good representation for the progenitor star for Supernova 1987A. The calculation was performed using the Piecewise-Parabolic Method for hydrodynamics on a two-dimensional spherical grid with rotational symmetry about the vertical axis and equatorial symmetry about the horizontal axis.

The grid contained 800 zones in the radial direction and 400 zones in the angular diraction and was allowed to expand homologously with the explosion to maintain as high a resolution as possible in the unstable layer during the evolution. The following sequences show the evolution of the density distribution as well as the distribution of hydrogen, helium, and oxygen within the ejecta to illustrate the amount of mixing caused by the instability. Each sequence shows the evolution in two reference frames.

In the first frame, the size of the plot expands with time as the grid expands. For the second reference frame, the size of the plot is kept fixed with the time so that more detail can be seen in the unstable layer.