Observed and predicted ratios of the horizontal and vertical components of the solar p-mode velocity eigenfunctions

We present evidence that the observed ratios of the horizontal and vertical components of the solar intermediate-degree p-mode velocity eigenfunctions closely match theoretical predictions of these ratios. This evidence comes from estimates of the observed eigenfunction component ratios that were obtained from the fitting of the p-mode oscillation peaks in low- and intermediate-degree (l ≤ 200) m-averaged power spectra computed from two different 60.75 day time series of Global Oscillation Network Group (GONG) project Dopplergrams obtained in late 1996 and early 1998. These fits were carried out using a peak-fitting method in which we fitted each observed p-mode multiplet with a model profile that included both the target mode and its six nearest spatial sidelobes and which incorporated the effects of the incomplete observational time series through the convolution of the fitted profiles with the temporal window functions, which were computed using the two actual GONG observing histories. The fitted profile also included the effects of the spatial leakage of the modes of differing degrees into the target spectrum through the use of different sets of m-averaged spatial leakage matrices. In order to study the sensitivity of the estimated component ratios to the details of the computation of the m-averaged power spectra and of the image-masking schemes employed by the GONG project, we generated a total of 22 different sets of modal fits. We found that the best agreement between the predicted and inferred ratios came from the use of unweighted averaged power spectra that were computed using so-called n-averaged frequency-splitting coefficients, which had been computed by cross-correlating the 2l + 1 zonal, tesseral, and sectoral power spectra at each l over a wide range of frequencies. This comparison yielded a total of 1906 pairs of predicted c_t,theory and fitted c_t,fit eigenfunction component ratios. A linear regression analysis of these pairs of ratios resulted in the following regression equation: c_t,fit = (0.0088 ± 0.0013) + (0.9940 ± 0.0044)c_t,theory. The resulting correlation coefficient was 0.9817. This agreement between the predicted and inferred ratios suggests that the predicted ratios should be used in the fitting of high-degree power spectra where the ratios cannot be inferred because of the blending together of individual modal peaks into broad ridges of power.