Resonant absorption of kink magnetohydrodynamic waves by a magnetic twist in coronal loops

Abstract

There is ample evidence of twisted magnetic structures in the solar corona. This motivates us to consider the magnetic twist as the cause of Alfven frequency continuum in the coronal loops, which can support the resonant absorption as a rapid damping mechanism for the observed coronal kink magnetohydrodynamic (MHD) oscillations. We model a coronal loop with a straight cylindrical magnetic flux tube which has constant but different densities in the interior and exterior regions. The magnetic field is assumed to be constant and aligned with the cylinder axis everywhere except a thin layer near the boundary of the flux tube which has an additional small magnetic field twist. Then, we investigate a number of possible instabilities that may arise in our model. In the thin tube thin boundary approximation, we derive the dispersion relation and solve it analytically to obtain the frequencies and damping rates of the fundamental (l=1) and first/second overtone (l=2,3) kink (m=1) MHD modes. We conclude that the resonant absorption by the magnetic twist can justify the rapid damping of kink MHD waves observed in coronal loops. Furthermore, the magnetic twist in the inhomogeneous layer can cause deviations from P1/P2=2 and P1/P3=3 which are comparable with the observations.

23 pages, 9 figures, matched to published version

References in corpus (7)

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• Resonant Absorption of Transverse Oscillations and Associated Heating in a Solar Prominence. II- Numerical aspects
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• An MHD avalanche model of multi-threaded coronal loop
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Cited by in corpus (9)

• Energetics of the Kelvin-Helmholtz instability induced by transverse waves in twisted coronal loops
• Observations of excitation and damping of transversal oscillation in coronal loops by AIA/SDO
• 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 flow on resonant absorption of slow MHD waves in magnetic flux tubes
• The effect of magnetic twist on resonant absorption of slow sausage waves in magnetic flux tubes
• The Effect of Flow and Magnetic Twist on Resonant Absorption of Slow MHD Waves in Magnetic Flux Tubes
• Resonant Absorption of Kink MHD Waves in Inclined and Asymmetric Coronal Loops