The possible effects of magnetic fields on laser experiments of Rayleigh–Taylor instabilities

The interaction of a blast wave generated in a supernova explosion with a composition discontinuity in the star's envelope produces crossed density and pressure gradients that are unstable to the growth of Rayleigh–Taylor modes. This instability is thought to be responsible for mixing of nuclear species in the ejecta and to produce observable effects in the light curve and spectrum of the explosion. Blast-wave-driven instabilities of this type have been studied extensively by numerical simulation as well as experimentally using the Omega Laser at the University of Rochester. Initial comparisons between the numerical simulations and the experiments show poor agreement. The simulations show the bubble and spike morphology of the classic Rayleigh–Taylor instability, with well-developed mushroom caps at the tips of the spikes. However, the mushroom caps seem to be completely absent from experiments with three-dimensional initial seed perturbations and are smaller than expected in two-dimensional experiments. Also, some experiments show mass extending beyond the spikes and penetrating almost to the shock front. This effect is completely absent from the numerical simulations. This paper discusses the possibility that the morphology of the instability is significantly altered by the generation of very strong magnetic fields during the laser experiments.