Meridional Circulation Variability from Large-Aperture Ring Diagrams
Irene González Hernández
Rudi Komm
Thierry Corbard
Frank Hill
Rachel Howe
Deborah Haber
Introduction
Local Helioseismology. Ring Diagrams Technique
Large-Aperture Ring Diagrams
Meridional Circulation variability
Conclusions
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
Ring Diagrams technique
1664 min
16o
Ring Diagrams technique
Synoptic Maps from Ring Diagrams
Large-Aperture Ring Diagrams
Rotation rate from Ring Diagrams
15° patches 30° patches
Meridional Circulation Variability
Meridional Circulation Countercell
Meridional Circulation Variability
Meridional Circulation Variability
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 Ro 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.