Simulation of Radiation-Driven Instabilities

实验室天体物理学是一个日益活跃的研究课题，实验室实验是天体物理物体和现象的尺度模拟。到目前为止，大多数实验室天体物理活动都集中在等离子体物理上。然而，最近有人提出，冷原子气体可以作为天体物理系统的类似物发挥有用的作用，在这些系统中，光通过高度不透明、强散射的介质相互作用和传播，例如恒星大气。人们对这些系统中出现的现象非常感兴趣，例如光子气泡，这种局域结构是由于辐射压力和重力之间的相互作用而产生的，并允许恒星产生超过通常爱丁顿极限的增强局域光度。最近的理论工作预测，在实验室中，可以在寒冷、稠密的原子气体中产生类似的光子气泡。这项工作中使用的理论模型包括一些简化的假设，如多次散射引起的扩散光在气体中的传播和原子气体的流体模型。在这个项目中，将开发一个光-气体相互作用的微观计算模型，该模型描述了在入射和散射光场的作用下原子系综的运动。该模型将允许扩展光子气泡形成理论，以便能够研究*有限光学深度*动力学效应的作用*从稳定气泡到湍流的转变*光学偶极力的作用及其与辐射压力力的相互作用最终，该模型将用于确定在实验室中可以观察到辐射压力驱动的不稳定性(如光子气泡和相关现象)的条件，并刺激原理验证实验。

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.