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.

arXiv commentAccepted for publication in Physical Review Letters

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• Generalized universal instability: Transient linear amplification and subcritical turbulence
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• Pressure-anisotropy-induced nonlinearities in the kinetic magnetorotational instability
• Simulating the magnetorotational instability on a moving mesh with the shearing box approximation
• Magnetorotational Dynamo Action in the Shearing Box
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• Linking dissipation-induced instabilities with nonmodal growth: the case of helical magnetorotational instability
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• The non-modal onset of the tearing instability
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• 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
• Non-modal Simon-Hoh instability of a plasma with a shearing Hall current
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