Imaging the Solar Tachocline by Time-Distance Helioseismology - Astrophysics > Solar and Stellar AstrophysicsReport as inadecuate




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Abstract: The solar tachocline at the bottom of the convection zone is an importantregion for the dynamics of the Sun and the solar dynamo. In this region, thesound speed inferred by global helioseismology exhibits a bump of approximately0.4% relative to the standard solar model. Global helioseismology does notprovide any information on possible latitudinal variations or asymmetriesbetween the Northern and Southern hemisphere. Here, we develop a time-distancehelioseismology technique, including surface- and deep-focusing measurementschemes and a combination of both, for two-dimensional tomographic imaging ofthe solar tachocline that infers radial and latitudinal variations in the soundspeed. We test the technique using artificial solar oscillation data obtainedfrom numerical simulations. The technique successfully recovers major featuresof the simplified tachocline models. The technique is then applied to SOHO-MDImedium-l data and provides for the first time a full two-dimensionalsound-speed perturbation image of the solar tachocline. The one-dimensionalradial profile obtained by latitudinal averaging of the image is in goodagreement with the previous global helioseismology result. It is found that theamplitude of the sound-speed perturbation at the tachocline varies withlatitude, but it is not clear whether this is in part or fully an effect ofinstrumental distortion. Our initial results demonstrate that time-distancehelioseismology can be used to probe the deep interior structure of the Sun,including the solar tachocline.



Author: Junwei Zhao, Thomas Hartlep, A. G. Kosovichev, N. N. Mansour

Source: https://arxiv.org/



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