The standard magnetorotational instability (SMRI) is a promising mechanism for turbulence and rapid accretion in astrophysical disks. It is a magnetohydrodynamic (MHD) instability that destabilizes otherwise hydrodynamically stable disk flow. Due to its microscopic nature at astronomical distances and stringent requirements in laboratory experiments, SMRI has remained unconfirmed since its proposal, despite its astrophysical importance. Here we report a nonaxisymmetric MHD instability in a modified Taylor-Couette experiment. To search for SMRI, a uniform magnetic field is imposed along the rotation axis of a swirling liquid-metal flow. The instability initially grows exponentially, becoming prominent only for sufficient flow shear and moderate magnetic field. These conditions for instability are qualitatively consistent with SMRI, but at magnetic Reynolds numbers below the predictions of linear analyses with periodic axial boundaries. Three-dimensional numerical simulations, however, reproduce the observed instability, indicating that it grows linearly from the primary axisymmetric flow modified by the applied magnetic field.

标准磁旋转不稳定性（SMRI）是天体物理盘中湍流和快速吸积的一种有前途的机制。这是一种磁流体动力学 (MHD) 不稳定性，会破坏原本流体动力学稳定的盘流。由于其在天文距离上的微观性质以及实验室实验的严格要求，尽管 SMRI 具有天体物理学的重要性，但自提出以来一直未经证实。在这里，我们报告了修改后的 Taylor-Couette 实验中的非轴对称 MHD 不稳定性。为了寻找 SMRI，沿着旋转液态金属流的旋转轴施加均匀磁场。不稳定性最初呈指数增长，只有在足够的流剪切和适度的磁场下才变得突出。这些不稳定条件在质量上与 SMRI 一致，但磁雷诺数低于具有周期性轴向边界的线性分析的预测。然而，三维数值模拟再现了观察到的不稳定性，表明它是从受外加磁场修改的初级轴对称流线性增长的。