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Tsing Hua University, Taiwan
Measurements of Acoustic Waves Scattered by Sunspots
(Stanford, April 2011, LoHCo Workshop)
Dean-Yi Chou
Hui ZhaoMing-Hsu Yang
Collaborators: Collaborators:
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Waves Scattered by a Sunspot Waves Scattered by a Sunspot
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Cameron et al. 2008Cameron et al. 2008
The incident wave is a plane wave The incident wave is a plane wave packet. packet.
Cross-correlation between the reference Cross-correlation between the reference line and each pointline and each point
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DataDataHMI: 30 July – 5 August 2010 (13,583 frames) HMI: 30 July – 5 August 2010 (13,583 frames)
NOAA 11092NOAA 11092
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The cross-correlation function relates to the wave function, The cross-correlation function relates to the wave function, but is but is notnot the wave function!!! the wave function!!!
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Comparison of CCF and WaveComparison of CCF and Wave
• Initially, the wave is narrower than the Initially, the wave is narrower than the CCF. CCF.
• As it propagates, the width of wave As it propagates, the width of wave increases faster than the width of CCFincreases faster than the width of CCF
because of dispersion. because of dispersion.
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Interference Patterns Interference Patterns from total wavesfrom total waves
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A Phenomenological Model A Phenomenological Model
wave equation in QSwave equation in QS
σ describes magnetic regions σ describes magnetic regions
wave equation with magnetic fieldswave equation with magnetic fields
solution solution
If If
Green’s function Green’s function
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Scattered Waves from a Model Scattered Waves from a Model
constant σ inside the circular areaconstant σ inside the circular area
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The EndThe End