Simulation of Radiation-Driven Instabilities

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Laboratory astrophysics, where laboratory experiments act as scale analogues of astrophysical objects and phenomena, is a topic of increasing research activity. To date, most laboratory astrophysics activity has concentrated on plasma physics. However, it was suggested recently that cold atomic gases could play a useful role as analogues for astrophysical systems where light interacts and propagates through highly opaque, strongly scattering media such as stellar atmospheres. There is significant interest in phenomena which arise in these systems e.g.photon bubbles, localised structures which arise due to the interplay between radiation pressure and gravity and allow stars to produce enhanced localised luminosities which exceed the usual Eddington limit. Recent theoretical work has predicted that analogues of photon bubbles could be produced in the laboratory in a cold, dense atomic gas. The theoretical models used in this work involved some simplifying assumptions e.g. diffusive light propagation in the gas due to multiple scattering and a fluid model of the atomic gas. In this project a microscopic, computational model of the light-gas interaction will be developed which describes the motion of an ensemble of atoms under the action of incident and scattered light fields. This model will allow extension of the theory of photon bubble formation to allow investigation of e.g.* finite optical depth* the role of kinetic effects* the transition from stable bubbles to turbulence* the role of optical dipole forces and their interplay with radiation pressure forcesUltimately, the model will be used to determine the conditions under which radiation-pressure driven instabilities such as photon bubbles and related phenomena could be observed in the laboratory and stimulate proof-of-principle experiments.