Meridional Circulation from ring-diagram analysis

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Meridional Circulation from ring-diagram analysis

• Irene González Hernández
• and the GONG team
• National Solar Observatory
• Tucson, Arizona

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Meridional Circulation from ring-diagram analysis

• Science motivation
• Meridional circulation from ring analysis. A
  quick history
• Recent results
• The future
• Conclusions

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Meridional Circulation and Dynamo Models

• Dikpati, Mausumi Gilman, Peter A.
  "Flux-Transport Dynamos with a-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

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A quick history of Meridional Circulation from
rings

• González Hernández, I, Patr?n, 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

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Meridional Circulation from rings
Basu Antia, 2003
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Meridional Circulation from rings
Haber et al, 2002
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Meridional Circulation from rings
González Hernández et al, 2006
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Meridional Circulation from rings
González Hernández et al, 2006
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Meridional Circulation from rings
Zaatri et al, 2006
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Meridional Circulation from rings
Zaatri et al, 2006
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Recent results from MDI
Courtesy of D. Haber
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Recent results from GONG
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Recent results from GONG
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Meridional Circulation from small patches
Courtesy of B. Hindman and D. Haber
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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)

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Conclusions

• 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