Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2012-04-09
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
14 pages, 5 figures
Scientific paper
We present a global-in-radius linear analysis of the axisymmetric magnetorotational instability (MRI) in a collisional magnetized plasma with Braginskii viscosity. For a galactic angular velocity profile $\Omega$ we obtain analytic solutions for three magnetic field orientations: purely azimuthal, purely vertical and slightly pitched (almost azimuthal). In the first two cases the Braginskii viscosity damps otherwise neutrally stable modes, and reduces the growth rate of the MRI respectively. In the final case the Braginskii viscosity makes the MRI up to $2\sqrt{2}$ times faster than its inviscid counterpart, even for \emph{asymptotically small} pitch angles. We investigate the transition between the Lorentz-force-dominated and the Braginskii viscosity-dominated regimes in terms of a parameter $\sim \Omega \nub/B^2$ where $\nub$ is the viscous coefficient and $B$ the Alfv\'en speed. In the limit where the parameter is small and large respectively we recover the inviscid MRI and the magnetoviscous instability (MVI). We obtain asymptotic expressions for the approach to these limits, and find the Braginskii viscosity can magnify the effects of azimuthal hoop tension (the growth rate becomes complex) by over an order of magnitude. We discuss the relevance of our results to the local approximation, galaxies and other magnetized astrophysical plasmas. Our results should prove useful for benchmarking codes in global geometries.
Mestel A. J.
Rosin M. S.
No associations
LandOfFree
Global MRI with Braginskii viscosity in a galactic profile does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Global MRI with Braginskii viscosity in a galactic profile, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Global MRI with Braginskii viscosity in a galactic profile will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-652348