1. Global Dynamics Rachel Howe, NSO Session H10

2. Synopsis Achievements from GONG/MDI –Nearly a full 11yr cycle of observations –Zonal flow pattern in bulk of convection zone. –Tachocline oscillations(?) –Comparisons with dynamo models Outstanding challenges –Systematics –High-l modes –Near-surface shear –Tachocline –Meridional Flow

3. Almost a cycle of observations! Zonal flow residuals from MDI (yearly averages)

4. Migrating Zonal Flows in the Interior Amplitude and phase of 11yr sinusoid fits

5. Rotation speed variations at the tachocline? ?

6. Systematic differences, e.g., between MDI and GONG, mostly but not all from analysis. Somewhat understood, but not all fixed. Need to offer choice of methods? Different methods for different regimes? Challenges: Systematic Errors

7. Challenges: High-Degree Modes Probably only f-modes. Need different -- and difficult -- fitting techniques. [Rhodes, Reiter, Jefferies?] Could be useful for inversions, particularly for near-surface layers. Need to adjust inversion codes to accommodate high l.

8. Challenges: Near-Surface Shear Does shear reverse at high latitudes, or not? How sharp is the shear really? Can HMI help? –high-l modes

9. Challenges: Tachocline Longitudinal structure needs large-scale local methods. –Methods need developing. –May not be possible with rings, look at T-D? Radial structure ‘just’ needs accurate, consistent measurements of lowish- degree modes. –Improvements to fitting algorithms may help.

10. Challenges: Meridional Flow Return meridional flow much desired by theorists. –Not really a global-mode problem. –Possible indirect inferences from effects on zonal flows?