Back to Volume
Paper: Characterization of High-Degree Modes using MDI, HMI and GONG Data
Volume: 478, Fifty Years of Seismology of the Sun and Stars
Page: 173
Authors: Korzennik, S. G.; Eff-Darwich, A.; Larson, T. P.; Rabello-Soares, M. C.; Schou, J.
Abstract: We present the first characterization of high-degree modes (i.e., ℓ up to 900 or 1000), using three instruments and three epochs corresponding to the 2001, 2002 and 2010 MDI Dynamics runs. For 2001, we analyzed MDI full-disk Dopplergrams, while for 2002, we analyzed MDI and GONG full-disk Dopplergrams, and for 2012 we analyzed MDI, GONG and HMI full-disk Dopplergrams. These Dopplergrams were spatially decomposed up to ℓ = 900 or 1000, and power spectra for all degrees and all azimuthal orders were computed using a high-order multi-taper, power spectrum estimator. These spectra were then fitted for all degrees and all azimuthal orders, above ℓ = 100, and for all orders with substantial amplitude. Fitting at high degrees generates ridge characteristics, characteristics that do not correspond to the underlying mode characteristics. We used a sophisticated forward modeling to recover the best possible estimate of the underlying mode characteristics (mode frequencies, as well as linewidths, amplitudes and asymmetries). We present the first attempt to apply this method to three instruments and three epochs. The derived sets of corrected mode characteristics (frequencies, line widths, asymmetries and amplitudes) are presented and compared.
Back to Volume