Study of MRI in stratified viscous plasma configuration

TL;DR

This paper investigates the magneto-rotational instability in stratified viscous plasma disks, revealing asymmetries caused by the corotation condition and the influence of gravitational stratification on MRI behavior.

Contribution

It introduces a novel analysis of MRI considering stratification and the corotation theorem, highlighting asymmetries and damping effects in viscous plasma disks.

Findings

MRI exhibits asymmetry with respect to the equatorial plane due to corotation.

Complete damping of MRI occurs over a positive critical height.

Stratification influences MRI behavior even in ideal plasma conditions.

Abstract

We analyze the morphology of the Magneto-rotational Instability (MRI) for a stratified viscous plasma disk configuration in differential rotation, taking into account the so-called corotation theorem for the background profile. In order to select the intrinsic Alfv\'enic nature of MRI, we deal with an incompressible plasma and we adopt a formulation of the local perturbation analysis based on the use of the magnetic flux function as a dynamical variable. Our study outlines, as consequence of the corotation condition, a marked asymmetry of the MRI with respect to the equatorial plane, particularly evident in a complete damping of the instability over a positive critical height on the equatorial plane. We also emphasize how such a feature is already present (although less pronounced) even in the ideal case, restoring a dependence of the MRI on the stratified morphology of the gravitational field.