Abstract Details
Abstracts
Author: Matthew C Pharr
Requested Type: Consider for Invited
Submitted: 2023-03-24 15:51:01
Co-authors: F.Ebrahimi
Contact Info:
Columbia University
500 W 120th St
New York, NY 10027
United States
Abstract Text:
A family of global modes is shown to be unstable to nonaxisymmetric perturbations in a differentially rotating plasma containing longitudinal and azimuthal magnetic fields. In an unstratified cylindrical disk model, using both global eigenvalue stability analysis and linear global initial-value simulations, it is demonstrated that this instability dominates at strong magnetic fields where local standard magnetorotational instability (MRI) becomes stable. Unlike the standard MRI mode, which is concentrated in the high flow shear region, these distinct global modes (with low azimuthal mode numbers) are extended in the global domain and are Alfvén-continuum-driven unstable modes. As its mode structure and relative dominance over MRI are inherently determined by the global spatial curvature as well as the flow shear in the presence of a magnetic field, we call it the magneto-curvature (magneto-spatial-curvature) instability (https://doi.org/10.3847/1538-4357/ac892d). Consistent with the linear analysis, as the field strength is increased in the nonlinear simulations, a transition from MRI-driven turbulence to a state dominated by global non-axisymmetric modes is obtained. We extend our MHD analysis to also include the Hall terms. The linear stability and nonlinear calculations will be presented in both MHD and Hall-MHD models.
http://doi.org/10.3847/1538-4357/ac892d
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