Thermal noise and the stability of single sonoluminescing bubbles

The stability of a bubble levitated in an acoustic field under single bubble sonoluminescence conditions was numerically investigated taking thermal noise effects into consideration. Due to the microscopic size of a sonoluminescing bubble thermal noise is important to its surface and is found to cause small irregularities in its spherical shape. A stochastic differential equation in Langevin form is derived to describe the dynamics of a perturbation from the spherical and solved together with the Rayleigh-Plesset equation. The mechanisms responsible for the amplification of small irregularities are examined and a stability threshold is derived, which is in good agreement with experimental threshold data of Holt and Gaitan.