1. 日震学的未来与展望 赵俊伟 斯坦福大学汉森试验物理实验室

2. Outline Some outstanding problems HMI time-distance pipeline Validation of local helioseismology results

3. Some Outstanding Problems Continue to look for returning meridional flows near the bottom of the convection zone. Detection of emergence of active regions. Detection of g-modes. Disentangle the effect of magnetic field and thermal effect on acoustic travel time variations. Map the magnetic field below the sunspot.

4. Time-Distance Helioseismology Data Analysis Pipeline for SDO/HMI

5. Time-distance pipeline generates subsurface (up to 30Mm[?] below the photosphere) flow maps and sound-speed perturbation maps for the following two types: 1.Routine production: daily (nearly) full disk maps and synoptic maps 2.User selected areas (most likely, active regions)

6. 1. Routine Production Input Every 8 hours, we select 480-minute Doppler observations and make time-distance measurements. Inversions are done to derive subsurface flow fields and sound-speed perturbations. A total of 25 areas are selected and used to generate full-disk subsurface map.

7. 1. Routine Production Every 8 hours, we generate a nearly full-disk map. For every Carrington rotation, we generate a synoptic map, updated daily though.

8. Routine Production

9. 2. User Designated Area Users are free to select their interested active regions, and request a computation of cross-covariance or subsurface structures. Input output

10. Flow Chart for Time-Distance Pipeline

11. Tracking, Remapping, and Time-Distance Measurement Each of 25 areas is tracked with the Snodgrass rate at the center of the area, and each area has a dimension of 512x512x640 with a spatial sampling of 0.06 o /pixel, and a temporal cadence of 45 sec. Phase-speed filtering is then applied. After time-distance measurement, the resultant dimension becomes 256x256 with 0.12 o /pixel. annulus # phase speed (μHz/l) FWHM annulus range (deg) 1 3.40 1.00 0.54 – 0.78 2 4.00 1.00 0.78 – 1.02 3 4.90 1.25 1.08 – 1.32 4 6.592 2.149 1.44 – 1.80 5 8.342 1.351 1.92 – 2.40 6 9.288 1.173 2.40 – 2.88 7 10.822 1.895 3.12 – 3.84 8 12.792 2.046 4.08 – 4.80 9 14.852 2.075 5.04 – 6.00 10 17.002 2.223 6.24 – 7.68 11 19.133 2.03 7.68 – 9.12

12. Initial Results from HMI: Routine Production of Synoptic Maps

13. Power Spectrum and Time-Distance Diagram

14. Subsurface flow field at the depth of 1-3 Mm.

17. Map for Divergence (Supergranulation) Divergence computed from horizontal flow fields at the depth of 0- 1 Mm. Positive regions represent positive divergence, i.e., supergranules.

18. Plenty of Supergranulation! Every 8 hours, we have full-disk supergranulation maps at different depths. The plentiful data will be very useful for supergranulation studies.

19. Divergence times Vorticity Horizontal component of divergence multiplying the vertical component of vorticity represents kinetic helicity, in some sense. This value has clear latitudinal dependence, and that is mainly caused by the Coriolis force.

20. Synoptic Flow Chart (Large Scale Flows) This flow chart displays large scale flows comparable to the ring-diagram analysis. The original flow map has 3000x1000 vectors, but this map only has 120x40 vectors. This rotation covers from May 19 to June 17, 2010.

21. Interior Rotation and Meridional Flow Speed

22. An Example of User Designated Area

23. Flow Field beneath an Active Region

24. Validation of Some Time-Distance Helioseismology Results

25. Can We Trust Things Observed by Sound? How much can we trust this image of sound?

26. Undoubtedly, we need to evaluate how good our helioseismology results are before we fully trust them. One way to evaluate the technique is to compare results obtained from other helioseismic techniques. But we know, different techniques may give same wrong results. Another way to validate our analysis technique is to test it using realistic numerical simulations.

27. Derive Subsurface Flow Fields

28. Realistic Simulation of Solar Convection in Upper Convective Zone (Bob Stein et al.) Now, they have extended their simulation to 96×96×20Mm. Do these simulations of convection carry acoustic information we need?

29. Time-Distance Diagrams of Different Depths?

30. Acoustic Wave Propagation

31. How Close Is This Simulation to the Real Sun? simulationHinode G-Band simulationHinode G-Band

32. Can We Derive Interior Flow Fields Using Only Surface Oscillations? We have demonstrated the simulated data have acoustic waves propagating into the interior, and also, has nice power spectrum very similar to the Sun. Now, the question to us, can we infer the interior flow fields using just the surface oscillations?

33. Compare Inverted Results with Simulation: 0 – 1 Mm

34. Compare Inverted Results with Simulation: 1 – 2 Mm

35. Compare Inverted Results with Simulation: 2 – 3 Mm

36. Compare Inverted Results with Simulation: 3 – 4 Mm

37. Compare Inverted Results with Simulation: 4 – 5 Mm

38. Compare Inverted Results with Simulation: 5 – 6 Mm

39. Compare Inverted Results with Simulation: 6 – 7 Mm

40. Compare Inverted Results with Simulation: 7 – 8 Mm

41. Comparison Summary (numbers in parentheses are correlation coefficients obtained using 48Mm×48Mm simulation, as published in Zhao et al., ApJ, 2007) Seems that we can satisfactorily infer horizontal flow fields up to 8Mm into the interior using 96×96Mm numerical simulation. However, vertical flow fields remain a failure.

42. Time-Distance Far-Side Imaging

43. Four-skip measurement scheme Five-skip measurement scheme

44. Numerical Simulation of Global Wavefields (by Hartlep & Mansour) A linear code solving wave propagation equations, including only spherical degree from 0 to 170.

45. A Big Active Region: Radius 180Mm (a) Time-distance result when the active region is placed at the center of the far-side; (b) Model; (c) Time-distance result when the active region is placed near the limb of the far- side; (d) model.

46. A Medium-Size Active Region: Radius 90Mm (a) Time-distance result when the active region is placed at the center of the far-side; (b) Model; (c) Time-distance result when the active region is placed near the limb of the far- side; (d) model.

47. A Small Active Region: Radius 45Mm (a) Time-distance result when the active region is placed at the center of the far-side; (b) Model; (c) Time-distance result when the active region is placed near the limb of the far- side; (d) model.

48. Far-Side Images Are Not Always Trustworthy Essentially, when an active region is located near the limb on the earth-side, a “ghost” image may be found at its antipode.

49. Science is a wonderful thing if one does not have to earn one’s living at it. -----Albert Einstein

50. 路漫漫其修远兮,吾将上下而求索.路漫漫其修远兮,吾将上下而求索. 世之奇伟瑰怪非常之观,常在乎险远,世之奇伟瑰怪非常之观,常在乎险远, 而人之所罕至焉,故非有志者不能至也.而人之所罕至焉,故非有志者不能至也.