Role of noise in the initial stage of solidification instability

Evolution of the morphological instability at the initially flat interface of a nonfaceting crystal growing freely into its pure melt has been studied by a computer simulation. A stochastic differential equation for the spatial Fourier components of the interface was formed by adding Gaussian random-noise terms representing spontaneous temperature fluctuations to the deterministic Mullins-Sekerka result of linear stability analysis. The results of the simulation qualitatively reproduce recent experiments in succinonitrile in which the spatial Fourier spectrum was found to be extremely noisy. The noise level required in the simulation was found to agree qualitatively with a rough estimate of temperature-fluctuation effects