Meridional Circulation Variability from Large-Aperture Ring Diagrams - PowerPoint PPT Presentation

Meridional Circulation Variability from Large-Aperture Ring Diagrams Irene González Hernández & The GONG team

� Introduction � Meridional Circulation variability from Large-Aperture Ring Diagrams � Comparison between large and small patches

Introduction: Meridional Circulation and Dynamo Models � Dikpati, Mausumi; Gilman, Peter A. "Flux-Transport Dynamos with α -Effect from Global Instability of Tachocline Differential Rotation: A Solution for Magnetic Parity Selection in the Sun". ApJ, 559, 428 � Gilman, P.A and Miesch, M. "Limits of Meridional Circulation Below the Solar Convection Zone" ApJ, 611, 568. � Haber, Deborah A.; Hindman, Bradley W.; Toomre, Juri; Bogart, Richard S.; Larsen, Rasmus M.; Hill, Frank. "Evolving Submerged Meridional Circulation Cells within the Upper Convection Zone Revealed by Ring-Diagram Analysis". ApJ,570, 855 � McDonald, E.; Dikpati, M. "Evolution of Large-scale Solar Magnetic Fields in the Presence of a Multi-cell Meridional Flow". American Astronomical Society Meeting 204, #53.06 Courtesy of E. McDonald

Large-Aperture Ring Diagrams

Rotation rate from Ring Diagrams 15° patches 30° patches

Meridional Circulation Variability

Meridional Circulation Countercell

Meridional Circulation Countercell

Comparison between large and small patches

Comparison between large and small patches

Conclusions / Future work � Large-aperture ring diagrams are effective in order to search for differential rotation and meridional circulation in deeper layers under the solar surface. � The presence of the countercell/down flow and the systematic differences in the averaged horizontal flows between GONG and MDI are still under investigation. � The results obtained from analyzing 25 Carrington rotations show a slight increase in the magnitude of the meridional flows with depth; however, the major increase below 0.965 R o is suspected to be an artifact of the inversions. � There is a limit to the depth that can be reached using the standard Ring Diagram analysis due to the plane wave approximation used by the technique. � Our intention is to use GONG continuous velocity data to search for a meridional circulation variation with the solar cycle.