The effect of a twisted magnetic field on the phase mixing of the kink magnetohydrodynamic waves in coronal loops

TL;DR

This study investigates how twisted magnetic fields influence the phase mixing and energy cascade of kink MHD waves in coronal loops, revealing that even small twists significantly affect wave dynamics and symmetry.

Contribution

It provides a theoretical analysis of the impact of magnetic twist on kink wave phase mixing and symmetry breaking in coronal loops.

Findings

Twisted magnetic fields can alter the phase-mixing rate of Alfvén continuum modes.

Magnetic twist affects the decay rate of global kink oscillations.

Small twists can significantly influence energy cascade processes.

Abstract

There are observational evidences for the existence of twisted magnetic field in the solar corona. This inspires us to investigate the effect of a twisted magnetic field on the evolution of magnetohydrodynamic (MHD) kink waves in coronal loops. To this aim, we solve the incompressible linearized MHD equations in a magnetically twisted nonuniform coronal flux tube in the limit of long wavelengths. Our results show that a twisted magnetic field can enhance or diminish the rate of phase-mixing of the Alfv\'{e}n continuum modes and the decay rate of the global kink oscillation depending on the twist model and the sign of the longitudinal ($k_z$) and azimuthal ($m$) wavenumbers. Also our results confirm that in the presence of a twisted magnetic field, when the sign of one of the two wavenumbers $m$ and $k_z$ is changed, the symmetry with respect to the propagation direction is broken. Even a small amount of twist can have an important impact on the process of energy cascade to small scales.