Nonmodal growth of the magnetorotational instability

Abstract

We analyze the linear growth of the magnetorotational instability (MRI) in the short time limit using nonmodal methods. Our findings are quite different to standard results, illustrating that shearing wave energy can grow at the maximum MRI rate, $-d\Omega /d\ln r,$ for any choice of azimuthal and vertical wavelengths. In addition, by comparing the growth of shearing waves with static structures, we show that over short time-scales shearing waves will always be dynamically more important than static structures in the ideal limit. By demonstrating that fast linear growth is possible at all wavelengths, these results suggest that nonmodal linear physics could play a fundamental role in MRI turbulence.

Accepted for publication in Physical Review Letters

References in corpus (5)

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• A Local Model for Angular Momentum Transport in Accretion Disks Driven by the Magnetorotational Instability
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• The Super-Alfvénic Rotational Instability in accretion disks about black holes
• Energy partition between Alfvénic and compressive fluctuations in magnetorotational turbulence with near-azimuthal mean magnetic field
• The impact of magnetic fields on momentum transport and saturation of shear-flow instability by stable modes
• Transient growth of perturbations on scales beyond the accretion disc thickness
• Revisiting Kinematic Fast Dynamo in 3-dimensional magnetohydrodynamic plasmas: Dynamo transition from non-Helical to Helical flows
• Aerodynamic sound of turbulent time-developing shear layer as the outcome of the flow linear non-modal instability