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arXiv 0907.2118astro-ph.SR
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利用时距日震学对太阳速跃层成像

Imaging the Solar Tachocline by Time-Distance Helioseismology

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

摘要:

对流层底部的速跃层是太阳动力学和太阳发电机的重要区域。在该地区,全球日震学推断的声速相对于标准太阳模型有约0.4%的波动。全球日震学没有提供任何关于南北半球之间可能的纬度变化或不对称的信息。在这里,我们开发了一个时间-距离日震学技术,包括表面和深聚焦测量方案和两者的组合,用于太阳速跃层的二维断层成像,推断径向和纬度的变化,在声速。我们测试的技术使用人工太阳振荡数据从数值模拟。该技术成功地恢复了简化的速度跃层模型的主要功能。然后,该技术被应用到SOHO/MDI中-l数据,并提供了第一次完整的二维声速扰动图像的太阳速跃层。经纬向平均得到的一维径向剖面与以往的全球日震观测结果吻合较好。据发现,声速扰动的振幅在速跃层随纬度而变化,但目前还不清楚这是否是部分或全部仪器失真的影响。我们的初步结果表明,时间-距离日震学可以用来探测太阳的深层内部结构,包括太阳速跃层。

英文摘要:

The solar tachocline at the bottom of the convection zone is an important region for the dynamics of the Sun and the solar dynamo. In this region, the sound speed inferred by global helioseismology exhibits a bump of approximately 0.4% relative to the standard solar model. Global helioseismology does not provide any information on possible latitudinal variations or asymmetries between the Northern and Southern hemisphere. Here, we develop a time-distance helioseismology technique, including surface- and deep-focusing measurement schemes and a combination of both, for two-dimensional tomographic imaging of the solar tachocline that infers radial and latitudinal variations in the sound speed. We test the technique using artificial solar oscillation data obtained from numerical simulations. The technique successfully recovers major features of the simplified tachocline models. The technique is then applied to SOHO/MDI medium-l data and provides for the first time a full two-dimensional sound-speed perturbation image of the solar tachocline. The one-dimensional radial profile obtained by latitudinal averaging of the image is in good agreement with the previous global helioseismology result. It is found that the amplitude of the sound-speed perturbation at the tachocline varies with latitude, but it is not clear whether this is in part or fully an effect of instrumental distortion. Our initial results demonstrate that time-distance helioseismology can be used to probe the deep interior structure of the Sun, including the solar tachocline.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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