EXCITATION AND DAMPING
OF
TRANSVERSAL CORONAL
LOOP OSCILLATIONS
Jaume Terradas
Ramón Oliver
José Luis Ballester
Universitat de les Illes Balears
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INTRODUCTION
•
Loop oscillations:
– transversal displacements of
the loop axis (kink mode)
– fixed footpoints: line-tying
– amplitude of oscillation
attenuates quickly with time
DAMPING MECHANISM
Ireland & De Moortel 2002
•Resonant absorption
•Phase mixing
•Leakage
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LOOP MODEL
3D
TUBE MODEL
2D
SLAB MODEL
1D
SLAB MODEL
(kink mode)
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MHD EQUATION AND SOLUTION
UNIFORM
MODEL
fast mode
kink mode
Lamb 1905
DAMPING WITH TIME
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MHD EQUATION AND SOLUTION
UNIFORM
MODEL
fast mode
kink mode
Lamb 1905
DAMPING WITH TIME
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NUMERICAL SOLUTION (I)
SLAB MODEL
NUMERICAL SOLUTION
Aschwanden et al. 2003
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NUMERICAL SOLUTION (II)
DENSE AND WIDE LOOPS
WAVELET
WAVELET
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CONCLUSIONS
• Thin, not too dense loops attenuate as t-1/2 and oscillate at the
cut-off frequency.
• Thicker and denser loops attenuate with different profiles and
lead to the excitation of the eigenmode.
• Attenuation with time, unrelated to any dissipation mechanism.
• Model too simple to compare with observations.
• More realistic models need to be considered:
• Slab model in 2D: kink mode + additional modes.
• Tube models (3D)
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