Helioseismic Probing of Convection Zone Dynamics

太阳对流区动力学的研究需要在日震逆理论方面取得实质性进展，以便开发新的分析技术，以便更好地利用全球振荡网络组（GONG）和其他日震观测提供的高度振荡数据。高度振荡的波场畸变和频率分裂应该允许人们测量太阳表面下对流区的大规模流动和相关的温度波动。该项目将发展和完善先进的反演技术，以解释波场中观察到的频率分裂和畸变，采用两种方法。第一种方法是利用从三维傅立叶变换中获得的功率谱环图，对流场和热场进行马赛克映射，这些环的详细形状和位移取决于被评估的每个小区域内的平均速度及其梯度。最近利用初步环图分析发现地表以下可能存在带状喷流，这为这项工作增添了强大的动力。第二种方法使用声波序列的希尔伯特变换，分析它们的相位和振幅变化，以检测由底层温度和磁场引起的波传播速度变化。当畸变波包穿过对流单元集合时，希尔伯特变换提供的相位信息被用作反演程序的输入，以获得声速变化的空间图。环图和希尔伯特波列分析是互补的：环分析是一个鲁棒的局部过程，为了简单起见牺牲了某些全局信息，而希尔伯特技术更复杂，在广泛分离的流动区域中关联相以获得比傅里叶技术可能获得的更高的空间分辨率。这两种方法都是理解太阳对流区如何运作的关键。这些程序将首先应用于目前由国家太阳天文台用高阶日震计（HDH）获得的高阶振荡数据，以便将它们发展为日后用于其他日震数据集的完善工具，包括由nsf资助的GONG项目和SOHO航天器上的SOI-MDI仪器提供的数据集。＊＊＊

Toomre 9417337 The study of the dynamics of the solar convection zone requires substantial advances in helioseismic inverse theory in order to develop new analysis techniques that are needed to make good use of the highdegree oscillation data to be provided by the Global Oscillations Network Group (GONG) and by other helioseismology observations. The wave-field distortions and frequency splittings of high-degree oscillations should allow one to measure large-scale flows and associated temperature fluctuations in the convection zone immediately beneath the surface of the sun. This project will develop and refine advanced inversion techniques to interpret the observed frequency splittings and distortions in the wave field following two approaches. The first employs ring diagrams of power spectra obtained from 3-D Fourier transforms to do mosaic mapping of the flow fields and thermal fields, with the detailed shapes and displacements of such rings depending upon the averaged velocities and their gradients within each of the small areas being assessed. The recent potential discovery of zonal jets below the surface using preliminary ring-diagram analysis adds strong impetus to this work. The second method uses Hilbert Transforms of acoustic wave trains, analyzing their phase and amplitude variations to detect changes in wave propagation speeds caused by underlying temperature and magnetic fields. Phase information provided by the Hilbert transform of distorted wave packets as they travel through an assembly of convection cells is used as input to inversion procedures to obtain spatial maps of sound-speed variations. The ringdiagram and Hilbert wave-train analyses are complementary: ring analysis is a robust local procedure which sacrificeq certain global information for simplicity, whereas the Hilbert technique is more sophisticated, relating phases in widely separated regions of the flow to obtain higher spatial resolution than is possible by Fourier techniques. Both methods are essential to understanding how the solar convection zone operates. Such procedures will be first employed on high-degree oscillation data now being obtained at the National Solar Observatory with the HighDegree Helioseismometer (HDH) in order to develop them as refined tools for later use on other helioseismic data sets, including those to be provided by the NSF-funded GONG project and by the SOI-MDI instrument on the SOHO spacecraft. ***