2 Years of Meridional Circulation from GONG Ring Diagrams

Details 2 Years of Meridional Circulation from GONG Ring Diagrams 2 Years of Meridional Circulation from GONG Ring Diagrams

May 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agusmsp32a..01g&link_type=abstract

American Geophysical Union, Spring Meeting 2005, abstract #SP32A-01

Astronomy and Astrophysics

Astronomy

7522 Helioseismology

Scientific paper

Large Aperture Ring Diagram analysis has been used to search for meridional circulation variability using a 2-year GONG data series. This technique uses patches that are four times the size of the typically studied sections of 15 degrees in diameter, so we are able to recover information about lower l modes that penetrate deeper into the Sun. Although extending the working area allow us to reach further into the solar interior, there is a compromise between the size of the patch and the validity of the plane wave approximation used by the technique. In this particular study, we search for variability of the meridional flows as a function of depth for 25 consecutive Carrington rotations. We have studied patches of 30-degree diameter over the solar surface as they crossed the solar central meridian. The range of modes recovered with these larger regions goes down to l~100 and reach a maximum depth of approximately 0.96Rsun. 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 24 intervals of 1664 minutes covering each Carrington rotation from CR1985 to CR2009 (Jan-2002 to Dec-2003). Meridional circulation results from standard ring diagram analysis and this large-aperture technique are compared, as well as results obtained from two different instruments GONG and MDI. 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 Astrofisico de Canarias, and Cerro Tololo Interamerican Observatory.

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