Torsional oscillations of longitudinally inhomogeneous coronal loops

Abstract

We explore the effect of an inhomogeneous mass density field on frequencies and wave profiles of torsional Alfven oscillations in solar coronal loops. Dispersion relations for torsional oscillations are derived analytically in limits of weak and strong inhomogeneities. These analytical results are verified by numerical solutions, which are valid for a wide range of inhomogeneity strength. It is shown that the inhomogeneous mass density field leads to the reduction of a wave frequency of torsional oscillations, in comparison to that of estimated from mass density at the loop apex. This frequency reduction results from the decrease of an average Alfven speed as far as the inhomogeneous loop is denser at its footpoints. The derived dispersion relations and wave profiles are important for potential observations of torsional oscillations which result in periodic variations of spectral line widths. Torsional oscillations offer an additional powerful tool for a development of coronal seismology.

6 pages, 3 figures, accepted in A&A

References in corpus (2)

• Observation of coronal loop torsional oscillation
• Spectral line width decrease in the solar corona: resonant energy conversion from Alfv{é}n to acoustic waves

Cited by in corpus (10)

• Doppler shift oscillations in solar spicules
• Torsional Alfvén waves in solar partially ionized plasma: effects of neutral helium and stratification
• Torsional Alfven Waves in Solar Magnetic Flux Tubes of Axial Symmetry
• Radio seismology of the outer solar corona
• Torsional Alfvénic Oscillations Discovered in the Magnetic Free Energy During Solar Flares
• On the inverse transform of Laplace transforms that contain (products of) the parabolic cylinder function
• Long-period oscillations of active region patterns: least-squares mapping on second-order curves
• Torsional Alfven waves in stratified and expanding magnetic flux tubes
• A persistent quiet-Sun small-scale tornado. II. Oscillations
• Fast magnetohydrodynamic oscillation of longitudinally inhomogeneous prominence threads: an analogue with quantum harmonic oscillator