Nonaxisymmetric Rossby Vortex Instability with Toroidal Magnetic Fields in Radially Structured Disks

TL;DR

This paper analyzes how radial density structures and toroidal magnetic fields influence the Rossby vortex instability and magnetorotational instability in accretion disks, revealing magnetic stabilization effects.

Contribution

It provides a linear stability analysis of nonaxisymmetric Rossby vortex instability in magnetized, radially structured disks, highlighting magnetic fields' stabilizing role.

Findings

Density structures can be unstable to nonaxisymmetric modes.

Magnetic fields always stabilize Rossby vortex instability modes.

Results include threshold conditions and properties of unstable modes.

Abstract

We investigate the global nonaxisymmetric Rossby vortex instability in a differentially rotating, compressible magnetized accretion disk with radial density structures. Equilibrium magnetic fields are assumed to have only the toroidal component. Using linear theory analysis, we show that the density structure can be unstable to nonaxisymmetric modes. We find that, for the magnetic field profiles we have studied, magnetic fields always provide a stabilizing effect to the unstable Rossby vortex instability modes. We discuss the physical mechanism of this stabilizing effect. The threshold and properties of the unstable modes are also discussed in detail. In addition, we present linear stability results for the global magnetorotational instability when the disk is compressible.