Two-dimensional simulations of strongly anisotropic supernova explosions of a nonrotating 15 M _ { \odot } blue supergiant progenitor are presented , which follow the hydrodynamic evolution from times shortly after shock formation until hours later .
It is shown that explosions which around the time of shock revival are dominated by low-order unstable modes ( i.e .
by a superposition of the l = 2 and l = 1 modes , in which the former is strongest ) , are consistent with all major observational features of SN 1987 A , in contrast to models which show high-order mode perturbations only and were published in earlier work .
Among other items , the low-mode models exhibit final iron-group velocities of up to \sim 3300 km/s , strong mixing at the He/H composition interface , with hydrogen being mixed downward in velocity space to only 500 km/s , and a final prolate anisotropy of the inner ejecta with a major to minor axis ratio of about 1.6 .
The success of low-mode explosions with an energy of about 2 \times 10 ^ { 51 } erg to reproduce these observed features is based on two effects : the ( by 40 % ) larger initial maximum velocities of metal-rich clumps compared to our high-mode models , and the initial global deformation of the shock .
The first effect protects the ( fastest ) clumps from interacting with the strong reverse shock that forms below the He/H composition interface , by keeping their propagation timescale through the He-core shorter than the reverse shock formation time .
This ensures that the outward motion of the clumps remains always subsonic , and that thus their energy dissipation is minimal ( in contrast to the supersonic case ) .
The second effect is responsible for the strong inward mixing of hydrogen : The aspherical shock deposits large amounts of vorticity into the He/H interface layer at early times ( around t = 100 s ) .
This triggers the growth of a strong Richtmyer-Meshkov instability that results in a global anisotropy of the inner ejecta at late times ( i.e .
around t = 10 000 s ) , although the shock itself has long become spherical by then .
The simulations suggest a coherent picture , which explains the observational data of SN 1987 A within the framework of the neutrino-driven explosion mechanism using a minimal set of assumptions .
It is therefore argued that other paradigms , which are based on ( more ) controversial physics , may not be required to explain this event .