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，从围绕原恒星形成的行星到围绕活动星系核的超大质量黑洞的吸积盘中。对于驱动此类圆盘耗散和角动量输运的湍流，提出了两种机制：(1)磁化和导电流的线性不稳定性，称为磁旋不稳定性（MRI）；(2)非线性水动力剪切流失稳。普林斯顿大学正在进行两个实验：液态金属实验研究MRI和相关的磁流体动力学（MHD）不稳定性，而流体动力学湍流实验研究非线性流体动力学过渡。最近，MHD实验在强轴向磁场中证明了非轴对称shercliff层的不稳定性，为在实验室中进行MRI的首次结论性演示铺平了明确的道路。目前对这一研究的贡献将集中在以下问题的实验研究上：(1)为什么准开普勒流抵抗湍流？(2) MRI、shercliff层不稳定性和其他MHD活动如何驱动角动量输运？这就需要为直接的全局扭矩测量增加关键的诊断，测量液态金属流动中的局部雷诺兹和麦克斯韦应力；并进行关键的硬件改进，以提高和控制旋转速度。这项研究将教育下一代科学家，并与地球物理学、流体动力学和等离子体物理学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.