Magnetic shear-driven instability and turbulent mixing in magnetized protostellar disks

TL;DR

This paper investigates a shear-driven instability in strongly magnetized protostellar disks, which can generate turbulence despite the suppression of other MHD instabilities, due to shear and compressibility effects.

Contribution

It introduces a new instability mechanism active in superthermal magnetic fields, expanding understanding of turbulence generation in protostellar disks.

Findings

The instability can grow within several rotation periods.

It operates even when traditional MHD instabilities are suppressed.

Provides a potential explanation for turbulence in strongly magnetized disks.

Abstract

Observations of protostellar disks indicate the presence of the magnetic field of thermal (or superthermal) strength. In such a strong magnetic field, many MHD instabilities responsible for turbulent transport of the angular momentum are suppressed. We consider the shear-driven instability that can occur in protostellar disks even if the field is superthermal. This instability is caused by the combined influence of shear and compressibility in a magnetized gas and can be an efficient mechanism to generate turbulence in disks. The typical growth time is of the order of several rotation periods.