Helioseismic Probing of Convection Zone Dynamics

对流区动力学的日震探测

• 批准号: 9417337
• 负责人: Juri Toomre
• 金额: $ 25.5万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-04-15 至 1999-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9417337&HistoricalAwards=false
• 关键词: Helioseismic; Probing; Convection; Zone; Dynamics

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. ***

图9417337太阳对流带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，这些技术是充分利用全球振荡网络小组和其他日震学观测所提供的高度振荡数据所必需的。高度振荡的波场扭曲和频率分裂应该使人们能够测量太阳表面正下方对流区的大范围流动和相关的温度波动。该项目将开发和改进先进的反演技术，以解释观测到的波场中的频率分裂和失真，方法有两种。第一种方法利用三维傅立叶变换得到的功率谱环形图来进行流场和热场的镶嵌映射，并根据每个小区域内的平均速度及其梯度来评估这些环形的详细形状和位移。最近利用初步环图分析可能在地表以下发现纬向喷流，这为这项工作增添了强大的推动力。第二种方法使用声波序列的希尔伯特变换，分析它们的相位和幅度变化，以检测由底层温度和磁场引起的波传播速度的变化。当扭曲的波包通过对流单元集合时，由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地图。环图和希尔伯特波列分析是相辅相成的：环图分析是一种稳健的局部程序，它为了简单而牺牲了某些全局信息，而希尔伯特技术则更复杂，它将流动的广泛分离区域中的相关联起来，以获得比傅立叶技术更高的空间分辨率。这两种方法对于理解太阳对流带是如何运行的都是必不可少的。这类程序将首先用于国家太阳天文台目前使用高度日震仪获得的高度振荡数据，以便将其开发为改进的工具，供以后用于其他日震数据集，包括将由美国国家科学基金会资助的GONG项目和SOHO航天器上的SOI-MDI仪器提供的数据。***