1. Meridional Circulation from ring-diagram analysis Irene González Hernández and the GONG++ team National Solar Observatory Tucson, Arizona

2. Meridional Circulation from ring-diagram analysis  Science motivation  Meridional circulation from ring analysis. A quick history  Recent results  The future  Conclusions

3. 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". 2001, ApJ, 559, 428  Gilman, P.A and Miesch, M. "Limits to Penetration of Meridional Circulation Below the Solar Convection Zone“, 2004, ApJ, 611, 568.  Giles, P., 2000, PhD Thesis, Stanford University.  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". 2002, ApJ,570, 855  McDonald, E.; Dikpati, M. "Evolution of Large-scale Solar Magnetic Fields in the Presence of a Multi-cell Meridional Flow". 2004,American Astronomical Society Meeting 204, #53.06 Courtesy of E. McDonald

4. A quick history of Meridional Circulation from rings  González Hernández, I, Patrόn, J, Bogart, R. S. and the SOI Ring Diagram Team, 1999, ApJ 510, L153  Basu, S. and Antia, H.M, 2002 Proceedings of the SOHO 11 Symposium  2003, ApJ 585, 553  Haber, D.A., Hindman, B. W.,Toomre, J., Bogart, R.S., Larsen, R.M., Hill, F.,2002, ApJ 570, 855.  González Hernández, I., Komm, R.,Hill,F.,Howe,R., Corbard, T. and Haber, D.A., 2006, ApJ 638, 576  Zaatri, A., Komm,R., Gonzalez Hernandez, I., Howe, R. and Corbard, T., 2006, SoPh 236, 227

5. Meridional Circulation from rings Basu & Antia, 2003

6. Meridional Circulation from rings Haber et al, 2002

7. Meridional Circulation from rings González Hernández et al, 2006

8. Meridional Circulation from rings González Hernández et al, 2006

9. Meridional Circulation from rings Zaatri et al, 2006

10. Meridional Circulation from rings Zaatri et al, 2006

11. Recent results from MDI Courtesy of D. Haber

12. Recent results from GONG++

14. Meridional Circulation from small patches Courtesy of B. Hindman and D. Haber

15. The future  GONG/MDI  Foreshortening / Projection  Differential rotation in the area studied  Effect of magnetic activity  fitting method  Other high latitude effects  HMI (Solar Dynamics Observatory)  VIM (Solar Orbiter)

16.  Ring analysis has made a big contribution to the study of meridional circulation from the surface to approx. 30Mm.  New results confirm solar cycle dependence close to the surface from previous works but show almost no dependence at deeper layers  Multi-cell circulation needs to be confirmed  We are limited in latitude to +/- 50 degrees  Higher resolution observations (HMI)  Observations off the ecliptic (Solar Orbiter mission)  Several problems of the technique need to be addressed Conclusions