Browsing by Subject "dissipative couette-flow"
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
Item Global Axisymmetric Magnetorotational Instability With Density Gradients(2008-05) Pino, Jesse; Mahajan, S. M.; Pino, Jesse; Mahajan, S. M.We examine global incompressible axisymmetric perturbations of a differentially rotating MHD plasma with radial density gradients. It is shown that the standard magnetorotational instability (MRI) criterion drawn from the local dispersion relation is often misleading. If the equilibrium magnetic field is either purely axial or purely toroidal, the problem reduces to finding the global radial eigenvalues of an effective potential. The standard Keplerian profile including the origin is mathematically ill-posed, and thus any solution will depend strongly on the inner boundary. We find a class of unstable modes localized by the form of the rotation and density profiles, with reduced dependence on boundary conditions.Item Spectrum Of Global Magnetorotational Instability In A Narrow Transition Layer(2009-06) Pino, Jesse; Mahajan, S. M.; Pino, Jesse; Mahajan, S. M.The global magnetorotational instability is investigated for a configuration in which the rotation frequency changes only in a narrow transition region. If the vertical wavelength of the unstable mode is of the same order or smaller than the width of this region, the growth rates can differ significantly from those given by a local analysis. In addition, the nonaxisymmetric spectrum admits overstable modes with a nontrivial dependence on azimuthal wavelength, a feature missed by the local theory. In the limit of vanishing transition region width, the Rayleigh-centrifugal instability is recovered in the axisymmetric case, and the Kelvin-Helmholtz instability in the nonaxisymmetric case.