Overview

1. Subsurface Circulations Established by Active RegionsBradley W. Hindman1,2Deborah A. Haber2Juri Toomre1,21Department of Astrophysical and Planetary Sciences2JILAUniversity of Colorado at Boulder

2. Overview • Quick primer of local helioseismology • Review of previously measured flows around active regions • New flow measurements

3. Local Helioseismology Two Basic Techniques to Measure Flows • Time-Distance Helioseismology • Ring Analysis Root Measurement Travel Time Difference Root Measurement Frequency Shift

4. Fundamental Observation (Dopplergram Movies)

5. Plane Wave Decomposition

6. Wave Power p10 Power is concentrated on discrete ridges Each ridge corresponds to a wave with a different number of radial nodes Frequency (mHz) p6 p4 p2 p1 f Wave Number - kR

7. Why Ridges? Acoustic waves are trapped within a spherical wave guide Deep Reflection Increasing sound speed with depth refracts waves back towards the surface Surface Reflection Waves reflect off the stellar photosphere because of the rapid decrease in mass density. Photosphere Photosphere Core Convection Zone

8. w kx ky Ring Analysis Power Since there are two spatial dimensions (x, y) and the time dimension t, the spectra are really 3D.

9. The Effects on p-Mode Spectra Tracked at the rotation rate No Tracking The above spectra was obtained by following the same patch of fluid as it rotates across the solar disk. This removes the large rotational velocity. The above spectra was obtained by studying the same area on the solar disk. Equatorial rotation results in a speed of ~ 2000 m/s.

10. Building up a Map The analysis is repeated over many positions on the solar surface to generate a 3D map of the flow as a function of the latitude, longitude and depth. The analysis is repeated on a daily basis to build up a time series of 3D flows. The size of the analysis tile determines the horizontal resolution

11. Flow Maps Depth 0-2 Mm AR9433

12. Previous Helioseismic MeasurementsActive Region Side View Plage Plage Sunspot Quiet Quiet Photosphere Moat flows (depth < 2 Mm) Surface inflows (depth < 7 Mm) Deep outflows (depth > 10 Mm)

13. Surface Inflows & Deep Outflows Plage Plage Sunspot Quiet Quiet Photosphere Moat flows (depth < 2 Mm) Surface inflows (depth < 7 Mm) Deep outflows (depth > 10 Mm)

14. Ring AnalysisAR9433 - April 2001 Surface Inflows (0 – 7 Mm) Deep Outflows (> 10 Mm) Haber et al. 2004

15. Sunspot Outflows Plage Plage Sunspot Quiet Quiet Photosphere Moat flows (depth < 2 Mm) Surface inflows (depth < 7 Mm) Deep outflows (depth > 10 Mm)

16. Moat Flows Obtained with f Modes Ring Analysis Time-Distance Helioseismology Jackiewicz et al. 2008 Haber 2009

17. Small-Scale Convective Flows Plage Plage Sunspot Quiet Quiet Photosphere

18. High-Resolution Ring Analysis Depth 0-2 Mm AR9433

19. Recent Results Flows used in this study have the following properties: • Flows possess a horizontal scale slightly larger than supergranulation (> 20 Mm). • Only f modes are used, thus the flows measured are an average over upper 2 Mm of the convection zone. • 201 days of data, spanning three years (2001-2003).

20. Derived Properties of Flows From the resulting flow fields we derive • Bulk motion of active regions • Mean active region inflows • Mean active region circulations

21. Bulk Motion of Active Regions Meridional Motion Trailing spot Plage Leading spot Zonal Motion (Rotation Rate)

22. Active & Quiet Mean magnetograms are used (from MDI) Two populations of pixels quiet |B | < 50 G active|B | > 50 G

23. Latitude {degrees} Bulk Motion of Active Regions (zonal flow) • Zonal flows are measured relative the mean differential rotation. • Active regions rotate more rapidly than quiet sun (~20 m/s). • Sunspots have been previously observed to super-rotate (~50 m/s) Mean Zonal Velocity Black – quiet Green- active Bars indicate daily variance in the means

24. Super-rotation of Magnetic Structures Sunspot Plage Photosphere • Intense, compact magnetic features rotate fastest. • Newly emerged features rotate faster than old features. Perhaps • Sunspots begin life more deeply rooted and are dragged across the surface more quickly than plage. • Dynamic disconnection of the field from its roots leads to deceleration. Rotational Speed Near Surface Shear Layer Deep fast flow drags the field 30 Mm

25. Bulk Motion of Active Regions (meridional flow) • Active regions advect poleward at the same rate as quiet sun. • This mean is sensitive to the plage and NOT the spots. Mean Meridional Velocity Black – quiet Green- active Latitude {degrees}

26. Meridional Advection of Magnetic Structures Conundrum If sunspots dynamically disconnect from their roots, one would expect passive meridional advection of older spots. This isn’t observed! Plage advects passively poleward (~20 m/s) Plage super-rotates (20 m/s) Plage Trailing spot Spots rotate fastest (50 m/s) Leading spot Sunspots don’t advect poleward!

27. Mean Circulations within Active Regions Inflows Circulation (counterclockwise)

28. 50 G 100 G 150 G 200 G 250 G Flux Levels Within Active Regions Example AR9433 Smoothed Magnetogram Active Region Sample All flux concentrations (B > 50 G) within the 2001-2003 Dynamics periods of MDI. Roughly 100 independent flux concentrations over 7 months.

29. Mean Inflow & Circulation Core (sunspots) Periphery Flows averaged over each flux contour, over all active regions, and over all days of data. Red– northern hemisphere Blue– southern hemisphere Periphery of active regions: inflows (20 m/s) cyclonic circulation (5 m/s). Cores of active regions (sunspots): outflows (50 m/s) anticyclonic circulation (10 m/s)

30. Mean Vorticity(related to the circulation) Black – quiet Green- active Mean Vertical Curl

31. Photosphere

33. Source of the Mean Flows Enhanced radiative cooling in plage Sunspot Plage photosphere Subduction Zone Downdraft

34. Coriolis forces acting on the inflows cause circulations.

35. Magnetic Shear The periphery of active regions and the spots rotate in opposite directions Magnetic Shear Wrapping Times: Periphery – 2000 days Sunspots – 150 days

36. Summary Large-scale Flow Patterns • Surface inflows into active regions (0 – 7 Mm), coupled to deep outflows out of active regions (> 10 Mm). • Surface outflows from sunspots ~ Moat Flows. • Subduction zone inside the plage (perhaps due to surface cooling) Rotational Shear • Periphery of active regions rotate cyclonically and the cores are anti-cyclones (consistent with the action of coriolis forces). Bulk Motion • Active regions rotate across the solar disk more quickly than quiet sun. • Active regions advect with the meridional flow.

37. Hurricanes: Driven by evaporation induced updrafts from a warm sea surface. Active Region Circulations: Driven by cooling induced downdrafts from magnetic plage.

39. Probability Density Functions (PDFs) Separate PDFs are computed for active and quiet pixels. Separate PDFs are computed for different latitudinal bands 11 bands 10° wide located at 10° intervals PDFs computed for zonal flow (rotation speed) meridional flow horizontal divergence vertical curl

40. Zonal & Meridional Flow PDFs Bands located at 30° latitude

41. Divergence and Vorticity PDFs Bands located at 30° latitude

42. Convective Symmetries Dashed – quiet sun Solid – active In quiet sun more of the surface is covered with upwelling outflows than downflowing inflows. Quiet Sun: Asymmetric distribution with a preference for outflows Active Regions: Symmetric distribution