2024/11/04 by Yin Wang, Wang, Yin, F. Ebrahimi +9 · 1 citation
Engineering · Physics and Astronomy · #FOS: Physical sciences #Fluid Dynamics and Turbulent Flows #High Energy Astrophysical Phenomena (astro-ph.HE) #Ionosphere and magnetosphere dynamics #Plasma Physics (physics.plasm-ph) #Solar and Space Plasma Dynamics
paper · pdf · doi:10.48550/arxiv.2411.02361
openalex publication_date 2024/11/04 · openalex created_date 2024/11/15 · openalex updated_date 2026/07/30
The standard magnetorotational instability (SMRI) is widely believed to be responsible for the observed accretion rates in astronomical disks. It is a linear instability triggered in the differentially rotating ionized disk flow by a magnetic field component parallel to the rotation axis. Most studies focus on axisymmetric SMRI in conventional base flows with a Keplerian profile for accretion disks or an ideal Couette profile for Taylor-Couette flows, since excitation of nonaxisymmetric SMRI in such flows requires a magnetic Reynolds number Rm more than an order of magnitude larger. Here, we report that in a magnetized Taylor-Couette flow, nonaxisymmetric SMRI can be destabilized in a free-shear layer in the base flow at Rm \gtrsim 1, the same threshold as for axisymmetric SMRI. Global linear analysis reveals that the free-shear layer reduces the required Rm, possibly by introducing an extremum in the vorticity of the base flow. Nonlinear simulations validate the results from linear analysis and confirm that a novel instability recently discovered experimentally (Nat. Commun. 13, 4679 (2022)) is the nonaxisymmetric SMRI. Our finding has astronomical implications since free-shear layers are ubiquitous in celestial systems.