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I. Gonzalez-Hernandez, R. Komm (National Solar Observartory), T. Corbard (L'Observatoire de la Cote d'Azur), F. Hill, R. Howe (National Solar Observartory)
Ring Diagram analysis, a local helioseismology technique, has proven very useful in the study of solar subsurface velocity flows to a depth of about 0.97Rsun. The depth range is determined by the modes recovered with this method and thus depends on the size of the area analyzed. Extending the working area allows us to detect lower l modes that penetrate deeper into the Sun. However, there is a compromise between the size of the patch and the validity of the plane wave approximation used by the technique.
Here we search for variability of the meridional flows as a function of depth for three consecutive Carrington rotations. We have studied patches of 30-degree diameter over the solar surface as they crossed the solar central meridian. These patches are twice the size of the typically studied sections of 15 degrees in diameter. The range of modes recovered with these larger regions goes down to l~100. A set of 15 overlapping sections, centered at latitudes 0 +/-7.5,+/-15,+/-22.5,+/-30.0,+/-37.5,+/-45.0 and +/-52.5, has been analyzed for 25 intervals of 1664 minutes in each Carrington rotation: CR1987, CR1988 and CR1989. Both GONG and MDI full disk Dopplergrams have been used for the work.
This work was supported in part by NASA grant NAG5-11703. SOHO is a project of international cooperation between ESA and NASA. This work utilizes data obtained by the Global Oscillation Network Group (GONG) Program, managed by the National Solar Observatory, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. The data were acquired by instruments operated by the Big Bear Solar Observatory, High Altitude Observatory, Learmonth Solar Observatory, Udaipur Solar Observatory, Instituto de Astrofisica de Canarias, and Cerro Tololo Interamerican Observatory.
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Bulletin of the American Astronomical Society, 36 #2
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