Experimental Studies of Convection in the Earth's Core

AurnouEAR-0229791本提案要求为加州大学洛杉矶分校一个新的实验流体力学实验室的工作提供资金。该实验室将利用两种新的强大的诊断技术来提供高分辨率、定量的地球外核对流模拟速度测量。这些结果将检验关于岩心流体中对流流动性质的长期持有的理论，并将提供几乎是行星参数值的流动动力学的详细特征。第一个项目将使用最近发展的声学多普勒测速技术来研究对流液体金属，其物理性质类似于熔融的外核。这些结果将检验旋转磁对流的线性稳定性理论，这是现代发电机理论的基础。这个稳定性理论是由Chandrasekhar在1950年代的S建立的，它只是先前一次达到渐近状态的实验研究的基础。第二个项目将利用光学技术粒子图像测速(PIV)，将其应用于对流水的旋转球壳，这是一种模拟外核的动力学和几何形状的装置。PIV将首次提供对流场(速度、涡度和螺旋度)的定量测量，这些流场被认为是地球发电机的基本组成部分，但从未通过实验手段得到充分测量。此外，实验设计将使PIV能够测量极地地区的对流，这些地区尚未得到广泛研究，但现在看来是重要的。总之，这些声学和光学测速技术将为岩心对流和地球动力学的数值和理论研究提供基准。它们还将产生迄今为止最高分辨率的实验对流数据，用于解释对地球深处的地磁和地震观测。

AurnouEAR-0229791This proposal requests funding for work in a new experimental fluidmechanics laboratory at UCLA. The lab will utilize two, new powerfuldiagnostic techniques to provide high-resolution, quantitative velocitymeasurements of simulated convection in the Earth's outer core. Theresults will test long-held theories regarding the properties ofconvective flows in core fluids and will provide a detailedcharacterization of flow dynamics at nearly planetary parameter values.The first project will use the recently developed technique of acousticDoppler velocimetry to study convecting liquid metals, which havephysical properties similar to that of the molten outer core. Theresults will test the linear stability theory of rotatingmagnetoconvection, the foundation of modern dynamo theory. Establishedby Chandrasekhar in the 1950's, this stability theory has only undergonea single prior experimental investigation that reached the asymptoticregime. The second project will utilize the optical technique ofparticle image velocimetry (PIV), applying it to a rotating sphericalshell of convecting water, a set-up that mimics the dynamics and thegeometry of the outer core. PIV will provide, for the first time,quantitative measurements of the flow fields (velocity, vorticity andhelicity) that are believed to be essential components of the geodynamo,but have never been measured adequately by experimental means.Furthermore, the experimental design will enable PIV to measureconvection in the polar regions, which have not been studied extensivelybut now appear to be significant. Together, these state-of-the-artacoustic and optical velocimetry techniques will provide benchmarks fornumerical and theoretical studies of core convection and the geodynamo.They will also generate the highest resolution experimental convectiondata to date for interpreting geomagnetic and seismic observations ofthe deep Earth.