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.