2008/10/09 by D. Salabert, R. A. García, Salabert, D. +2
Earth and Planetary Sciences · Physics and Astronomy · #Adaptive optics and wavefront sensing #Astrophysics (astro-ph) #FOS: Physical sciences #Geophysics and Gravity Measurements #Solar and Space Plasma Dynamics #astro-ph
paper · pdf · doi:10.48550/arxiv.0810.1696
4 pages, 5 figures, Conference proceeding GONG 2008 / SOHO XXI Meeting
openalex publication_date 2008/10/09 · arxiv created 2008/10/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
In the case of spatially-revolved helioseismic data (such as MDI, GONG, HMI), the usual mode-fitting analysis consists of fitting the 2l+1 individual m-spectra of a given multiplet (n, l) either individually or simultaneously. Such fitting methods fail to obtain reliable estimates of the mode parameters (frequency, splitting, ...) when the signal-to-noise ratio (SNR) is low, which makes those methods not suitable when one wants to look at the low-amplitude, long-lived solar p modes in the low-frequency range. Instead, Salabert et al. (2007) developed a new method to extract the mode parameters by adjusting the rotation- and structure-induced frequency shift for each m-spectrum to minimize the mode width in the m-averaged spectrum (a "collapsogram"). The m-averaged spectrum technique, applied to the spatially-resolved GONG and MDI data, appeared to be a powerful tool for low SNR modes in the low-frequency range. Another possibility to increase the SNR is to combine data from different instruments (Garcia et al. 2004a). We present here an adaptation of both techniques: the "collapsograms" applied to a combination of observations from a Sun-as-a-star instrument, GOLF, and a disk-imaged one, GONG.