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:

Waves Scattered by a Sunspot Waves Scattered by a Sunspot

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

DataDataHMI: 30 July – 5 August 2010 (13,583 frames) HMI: 30 July – 5 August 2010 (13,583 frames)

NOAA 11092NOAA 11092

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!!!

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.

Interference Patterns Interference Patterns from total wavesfrom total waves

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

Scattered Waves from a Model Scattered Waves from a Model

constant σ inside the circular areaconstant σ inside the circular area

The EndThe End