Thermomagnetic instability of a rotating magnetized plasma disk

TL;DR

This paper investigates a new instability mechanism in rotating magnetized plasma disks, which could trigger turbulence even when traditional magneto-rotational instability is suppressed, especially considering collisional effects and magnetic tension.

Contribution

It introduces a novel unstable mode in plasma disks that replaces magneto-rotational instability under certain conditions, incorporating non-zero Nernst effects and resistivity.

Findings

Identifies a new unstable mode with imaginary frequency leading to instability.

Shows the mode can induce turbulence even without magneto-rotational instability.

Demonstrates the role of collisional effects and magnetic tension in plasma stability.

Abstract

We analyze the stability of a thin plasma disk which is rotating around a compact astrophysical object and is embedded in the strong magnetic field of such a source. The aim of this study is the determination of a new type of unstable modes, able to replace the magneto-rotational instability profile for low beta-values and for sufficiently small scales of the perturbations, where it fails. In particular, we consider the magneto-hydrodynamical scheme including a non-zero Nernst coefficient, corresponding to first-order collisional effects. As a result, modes with imaginary frequency lead to an instability regime when the magnetic tension vanishes. Finally, we show that, even in the presence of resistive effects, it remains a good candidate to ensure the onset of a turbulent behavior in the absence of the magneto-rotational instability.