The effects of twisted magnetic field on coronal loops oscillations and dissipation

TL;DR

This paper investigates how twisted magnetic fields influence the oscillation frequencies and damping rates of coronal loop MHD modes, providing insights into wave behavior in magnetically complex solar structures.

Contribution

It derives and numerically solves the dispersion relation for MHD waves in twisted flux tubes, including damping effects due to viscosity and resistivity, which is a novel analysis of wave dissipation in such configurations.

Findings

Twisted magnetic fields alter the frequencies of kink and fluting waves.

Damping rates increase with magnetic twist, affecting wave longevity.

Numerical solutions reveal the significance of magnetic twist in wave dissipation.

Abstract

The standing MHD modes in a zero-$\beta$ cylindrical magnetic flux tube modelled as a straight core surrounded by a magnetically twisted annulus, both embedded in a straight ambient external field is considered. The dispersion relation for the fast MHD waves is derived and solved numerically to obtain the frequencies of both the kink ($m=1$), and fluting ($m=2,3$) waves. Damping rates due to both viscous and resistive dissipations in presence of the twisted magnetic field is derived and solved numerically for both the kink and fluting waves.