Stretching of the toroidal field and generation of magnetosonic waves in differentially rotating plasma

TL;DR

This paper investigates how differential rotation in magnetized plasma can amplify seed perturbations into significant magnetosonic waves, highlighting the role of magnetic field orientation and flow dynamics.

Contribution

It demonstrates that differential rotation can exponentially amplify seed perturbations into magnetosonic waves, emphasizing the importance of magnetic field orientation relative to the angular velocity gradient.

Findings

Seed perturbations can be amplified by several orders of magnitude.

Amplification requires a non-zero magnetic field component along the angular velocity gradient.

Differential rotation enhances the generation of magnetosonic waves.

Abstract

We evaluate the generation of magnetosonic waves in differentially rotating magnetized plasma. Differential rotation leads to an increase of the azimuthal field by winding up the poloidal field lines into the toroidal field lines. An amplification of weak seed perturbations is considered in this time-dependent background state. It is shown that seed perturbations can be amplified by several orders of magnitude in a differentially rotating flow. The only necessary condition for this amplification is the presence of a non-vanishing component of the magnetic field in the direction of the angular velocity gradient.