A Mode-Fitting Methodology Optimized for Very Long Helioseismic Time Series
A Mode-Fitting Methodology Optimized for Very Long Helioseismic Time Series
复制标题
针对超长日震时间序列优化的模态拟合方法
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
S. Korzennik
中科院分区：
文献类型：
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作者：
S. Korzennik
我描述并提出了一个新开发的拟合方法优化非常长的时间序列的结果。这种新方法的发展是由全球振荡网络组（GONG）和迈克尔逊多普勒成像仪（MDI）的五年多几乎不间断的观测推动的，填充因子分别高达82.2%和89.8%。最近，MDI团队制作的2088天长的球谐系数时间序列的可用性促使了这一点。拟合过程使用最佳正弦多锥度谱估计器，其中锥度的数量基于模式线宽、完整的泄漏矩阵（即，水平分量以及垂直分量），以及不对称模式分布，以利用单独参数化的分布同时拟合所有方位角阶次。该方法被应用到2088天长的时间序列的MDI和GONG观测，以及728天长的子集，和球谐度之间的1和25。将这些拟合得到的值进行相互比较（MDI与GONG），并与MDI团队和GONG项目的等效估计值进行比较。我还比较了拟合728天子集的结果与2088天时间序列的结果。这个比较显示了众所周知的频率随太阳活动的变化，以及它如何以几乎恒定的频率和m/l模式进行缩放。这种比较还显示了模式线宽的一些变化和模式不对称性的恒定性。
I describe and present the results of a newly developed fitting methodology optimized for very long time series. The development of this new methodology was motivated by the fact that we now have more than half a decade of nearly uninterrupted observations by the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI), with fill factors as high as 82.2% and 89.8%, respectively. It was recently prompted by the availability of a 2088 day long time series of spherical harmonic coefficients produced by the MDI team. The fitting procedure uses an optimal sine multitaper spectral estimator, with the number of tapers based on the mode line width, the complete leakage matrix (i.e., horizontal as well as vertical components), and an asymmetric mode profile to fit simultaneously all the azimuthal orders with individually parameterized profiles. This method was applied to 2088 day long time series of MDI and GONG observations, as well as 728 day long subsets, and for spherical harmonic degrees between 1 and 25. The values resulting from these fits are intercompared (MDI vs. GONG) and compared to equivalent estimates from the MDI team and the GONG project. I also compare the results from fitting the 728 day subsets to the result of the 2088 day time series. This comparison shows the well-known change of frequencies with solar activity and how it scales with a nearly constant pattern in frequency and m/l. This comparison also shows some changes in the mode line width and the constancy of the mode asymmetry.