SOHO CoRoT Kepler Picard SDO GONG
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Finite-wavelength scattering of high-degree modes by a sunspot

Auteur

Liang Zhi-Chao

Institution

Max Planck Institute for Solar System Research

Theme

Local helioseismology
Auteur(s) supplémentaire(s)L. Gizon, H. Schunker
Institution(s) supplémentaire(s)National Tsing Hua University, Taiwan

Abstract

Wave scattering is a very basic tool to learn about the structure of an object. In this study, we characterize the scattering of high-degree f and p modes by a sunspot, in a regime where the wavelength is comparable to the size of the sunspot. Wave travel times and amplitudes are extracted from the cross-covariance function of the random wave field. Several finite-wavelength properties emerge: i) wave front healing, ii) travel-time anomalies far from the central ray path, and iii) sidelobes of enhanced wave amplitude on each side of the central ray. These properties depend strongly on the wavelength/frequency of the incoming wave packet. We believe that such observations are important in order to correctly interpret seismic signatures of sunspots and other localized perturbations in the Sun.
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