Experiments in Magnetohydrodynamic and Hydrodynamic Instabilities of Astrophysical Interest

等离子体轨道能量的有效耗散发生在吸积盘中，从围绕原恒星形成行星的吸积盘，到活动星系核中超大质量黑洞周围的吸积盘。对于这类圆盘中驱动耗散和角动量输运的湍流，已经提出了两种机制：(1)称为磁致旋转不稳定(MRI)的磁化和导电流动的线性不稳定；(2)非线性流体动力剪切流不稳定。普林斯顿大学正在进行两个实验：液体-金属实验研究磁共振成像和相关的磁流体动力学(MHD)不稳定性，而流体动力湍流实验研究非线性流体动力学转变。最近，MHD实验证明了强轴磁场中强非轴对称Shercliff层的不稳定性，为在实验室中首次确凿地展示MRI铺平了道路。目前对这项研究的贡献将集中在以下问题的实验研究上：(1)为什么准开普勒流对湍流具有抵抗力？以及(2)MRI、谢尔克里夫层不稳定性和其他MHD活动是如何驱动角动量传输的？这需要增加关键的诊断功能，用于直接测量全局扭矩，测量液体-金属流动中的局部雷诺应力和麦克斯韦应力；以及进行关键的硬件改进，以提高和控制转速。这项研究将培养下一代科学家，并与地球物理、流体力学和等离子体物理等邻近学科建立联系，同时全面推进实验室天体物理学。

Efficient dissipation of the orbital energy of plasma occurs in accretion disks ranging from those in which planets form around protostars, to those around supermassive black holes in active galactic nuclei. Two mechanisms have been proposed for the turbulence that drives dissipation and angular-momentum transport in such disks: (1) a linear instability of magnetized and electrically conducting flow known as magnetorotational instability (MRI); and (2) nonlinear hydrodynamic shear-flow instability. Two experiments are running at Princeton: the Liquid-Metal experiment studies MRI and related magnetohydrodynamic (MHD) instabilities, while the Hydrodynamic Turbulence Experiment studies nonlinear hydrodynamic transitions. Recently, the MHD experiment has demonstrated robust nonaxisymmetric Shercliff-layer instabilities in strong axial magnetic fields, paving a clear path towards a first conclusive demonstration of MRI in the laboratory. The present contribution to this research will focus on experimental studies of the following questions: (1) Why are quasi-keplerian flows resistant to turbulence? and (2) How do MRI, Shercliff-layer instabilities, and other MHD activity, drive angular momentum transport? This requires adding crucial diagnostics for direct global torque measurements, measuring local Reynolds and Maxwell stresses in the liquid-metal flow; and making critical hardware improvements to increase and control rotation speeds. This research will educate the next generation of scientists and forge links with neighboring disciplines such as geophysics, fluid dynamics, and plasma physics, while advancing laboratory astrophysics generally.