The effect of twisted magnetic field on the resonant absorption of MHD waves in coronal loops

Abstract

The standing quasi modes in a cylindrical incompressible flux tube with magnetic twist that undergoes a radial density structuring is considered in ideal magnetohydrodynamics (MHD). The radial structuring is assumed to be a linearly varying density profile. Using the relevant connection formulae, the dispersion relation for the MHD waves is derived and solved numerically to obtain both the frequencies and damping rates of the fundamental and first-overtone modes of both the kink (m=1) and fluting (m=2,3) waves. It was found that a magnetic twist will increase the frequencies, damping rates and the ratio of the oscillation frequency to the damping rate of these modes. The period ratio P_1/P_2 of the fundamental and its first-overtone surface waves for kink (m=1) and fluting (m=2,3) modes is lower than 2 (the value for an untwisted loop) in the presence of twisted magnetic field. For the kink modes, particularly, the magnetic twists B_ϕ/B_z=0.0065 and 0.0255 can achieve deviations from 2 of the same order of magnitude as in the observations. Furthermore, for the fundamental kink body waves, the frequency bandwidth increases with increasing the magnetic twist.

arXiv comment18 pages, 9 figures

References in corpus (6)

• On Solving the Coronal Heating Problem
• On the nature of kink MHD waves in magnetic flux tubes
• Enhanced phase mixing of Alfvén waves propagating in stratified and divergent coronal structures
• The effects of twisted magnetic field on coronal loops oscillations and dissipation
• Resonant absorption in dissipative flux tubes
• The effect of density stratification on the resonant absorption of MHD waves in coronal loops

Cited by in corpus (14)

• Kink oscillations of coronal loops
• Transverse kink oscillations in the presence of twist
• The Effect of Twisted Magnetic Field on the Period Ratio P_1/P_2 of Nonaxisymmetric MHD Waves
• Kelvin-Helmholtz instability of kink waves in photospheric twisted flux tubes
• Axisymmetric Modes in Magnetic Flux Tubes with Internal and External Magnetic Twist
• Resonant absorption of kink magnetohydrodynamic waves by a magnetic twist in coronal loops
• The effect of a twisted magnetic field on the phase mixing of the kink magnetohydrodynamic waves in coronal loops
• Resonant absorption of kink oscillations in coronal flux tubes with continuous magnetic twist
• Phase Mixing of Kink MHD Waves in the Solar Corona: Viscous Dissipation and Heating
• The effect of magnetic twist on resonant absorption of slow sausage waves in magnetic flux tubes
• Torsional Alfven waves in stratified and expanding magnetic flux tubes
• The Effect of Flow and Magnetic Twist on Resonant Absorption of Slow MHD Waves in Magnetic Flux Tubes
• Transition to turbulence in nonuniform coronal loops driven by torsional Alfvén waves. II. Extended analysis and effect of magnetic twist
• Resonantly damped oscillations of elliptically shaped stratified emerging coronal loops