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SOT capabilities for local helioseismology and expected results

SOT capabilities for local helioseismology and expected results. Alexander Kosovichev Stanford University. Science objectives for local helioseismology on Solar-B. Quiet Sun Structure and dynamics of convective cells, supergranulation and mesogranulation

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SOT capabilities for local helioseismology and expected results

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  1. SOT capabilities for local helioseismology and expected results Alexander Kosovichev Stanford University 17th SOT Meeting NOAJ, April 17-20, 2006

  2. Science objectives for local helioseismology on Solar-B • Quiet Sun • Structure and dynamics of convective cells, supergranulation and mesogranulation • Dynamics of the high-latitude and polar regions • Meridional flow and flux transport (solar-cycle dynamo) • Structure and dynamics of supergranulation (properties of supergranulation waves) • Subsurface structure of small-scale magnetic elements • Active Regions • Emerging active regions • Active region evolution in sub-surface layers (tracking) • Kinetic and magnetic helicity (local dynamo) • Shearing and twisting flows in active regions, relationship to flares 17th SOT Meeting NOAJ, April 17-20, 2006

  3. Unique capabilities of Solar-B for helioseismology • Observations of high-latitude and polar regions (not accessible for MDI hi-res FOV). • Tracking of active regions for several days and monitoring subsurface dynamics. • Observations of wave scattering on magnetic elements and diagnostics of subsurface properties of small-scale structures. • Helioseismic and photospheric effects of solar flares. 17th SOT Meeting NOAJ, April 17-20, 2006

  4. Time-distance measurements Travel times are determined from the cross-covariance function (Duvall et al, 1993): 17th SOT Meeting NOAJ, April 17-20, 2006

  5. Deep- and surface-focusing observing schemes Surface focusing Deep focusing 17th SOT Meeting NOAJ, April 17-20, 2006

  6. SOHO/MDI Helioseismology Data • Full-disk Dopplergrams: • 2 arcsec/pixel; • 2-months a year continuous contact • High-resolution Dopplergrams: • 0.6 arcsec/pixel in the disk center • random 3-day campaigns 17th SOT Meeting NOAJ, April 17-20, 2006

  7. Time-distance depth range: 0 – 6 Mm; temporal resolution: 2-8 hours SOT Helioseismology Data This portion of the MDI Hi Res Field is 400x400 arcsec. The rectangle is the FPP Field, 320 x 160 arcsec. The square is the central 160 x 160 arcsec. 17th SOT Meeting NOAJ, April 17-20, 2006

  8. Helioseismology of polar regions • Solar-B has a unique capability to observe polar regions with high-resolution and measure their structure and dynamics, providing important data about the differential rotation and meridional circulation for dynamo models of the solar cycle. • Regular synoptic observations of polar regions are essential. 17th SOT Meeting NOAJ, April 17-20, 2006

  9. Internal differential rotation from MDI The high-latitude rotation has not been measured accurately. The areas of uncertainty are indicated by gray shadow. 17th SOT Meeting NOAJ, April 17-20, 2006

  10. Solar-cycle variations of meridional circulation 2002 2001 • MDI measurements show that the meridional circulation below the surface slows down at the solar maximum. • Slowing meridional circulation at the solar maximum creates difficulties for flux transport dynamo models to explain reversals of the polar magnetic fields. • However, the meridional flows in high-latitude regions have not been measured. 2000 1999 1998 1997 1996 17th SOT Meeting NOAJ, April 17-20, 2006

  11. Emergence and evolution of active regions • Solar-B will improve the resolution of sub-photospheric structure of emerging active regions and associated flows. 17th SOT Meeting NOAJ, April 17-20, 2006

  12. Magneticfield and horizontal flows during emergence of AR9393 2001.03.05_20:00 UT, d=2 Mm 17th SOT Meeting NOAJ, April 17-20, 2006

  13. Sub-surface structure and dynamics of sunspots • Helioseismology reveals subsurface converging flows below sunspots. However, the transition from the divergent Evershed and moat flows on the surface to the converging subsurface flows is unknown. 17th SOT Meeting NOAJ, April 17-20, 2006

  14. Diagnostics of subsurface magnetic fields Alfven speed can be measured from the anizotropy of travel-times. 17th SOT Meeting NOAJ, April 17-20, 2006 (Zhao & Kosovichev)

  15. High-resolution helioseismology (numerical simulations) • New large-scale realistic simulations of solar convection provide important tests of helioseismology methods and demonstrate the potential of high-resolution observations of solar oscillations. 17th SOT Meeting NOAJ, April 17-20, 2006

  16. Comparison of the oscillation power spectrum and the time-distance diagrams from MDI and numerical simulations. Analysis of the realistic simulations shows that high-resolution Solar-B data will allow us to improve the resolution of helioseismic images. 17th SOT Meeting NOAJ, April 17-20, 2006 Georgobiani et at 2006)

  17. Testing time-distance measurements with realistic numerical simulations Helioseismology measurement Simulation data 17th SOT Meeting NOAJ, April 17-20, 2006

  18. Magnetic features:Top: abs. value of 4-hour average mgtm.Middle: features above some levelBottom: features not close together Helioseismology of small-scale magnetic elements New idea: study the scattering of waves on small-scale magnetic elements (Duvall, 2005) 17th SOT Meeting NOAJ, April 17-20, 2006

  19. Observed and theoretical sensitivity functions for magnetic elements Data (Duvall) Model (Birch & Gizon) 17th SOT Meeting NOAJ, April 17-20, 2006 s/Mm^2/kG

  20. Future Work, Extensions, Ideas • What are we seeing ? B ? down-flow ? • Develop a physical model, maybe thin flux tube: test models of tube oscillations, do boundary conditions matter ? • Extend modeling to p-modes • Joint observations, can see waves coming up the magnetic element ? Courtesy of Aaron Birch 17th SOT Meeting NOAJ, April 17-20, 2006

  21. Helioseismology of flaring regions • Where and how does twisting of magnetic structures occur: in the subsurface layers or in the dynamo region? • What is the role of the local kinetic helicity in creating the magnetic helicity? • What are the origin and effect of the subsurface shearing flows? • How deep are the flows that control motions of the magnetic footpoints in the photosphere? • Are there links between sub-photospheric dynamics and magnetic energy storage and release in the chromosphere and corona? 17th SOT Meeting NOAJ, April 17-20, 2006

  22. Flares and kinetic helicity • There is evidence that kinetic helicity increases before major flares. Helicity density 17th SOT Meeting NOAJ, April 17-20, 2006 Zhao, 2004

  23. Magnetic field dynamics associated with flares and CME • Magnetic field topology and magnetic stresses in the solar atmosphere are likely be controlled by motions of magnetic flux footpoints below the surface However, the depth of these motions is unknown. • Time-distance helioseismology provides maps of subphotospheric flows and sound-speed structures, which can be compared with photospheric magnetic fields and X-ray data. 17th SOT Meeting NOAJ, April 17-20, 2006

  24. Time-distance helioseismology analysis of 2 flares of AR 10486: • X17.2 October 28, 2003, 9:51-11:24 UT • X10.0 October 29, 2003, 20:37-21:01 UT 17th SOT Meeting NOAJ, April 17-20, 2006

  25. Magnetic field changes in X10 flare, Oct. 29, 2003, 20:37 UT 17th SOT Meeting NOAJ, April 17-20, 2006

  26. 29-10-2004, 20:37 UT 17th SOT Meeting NOAJ, April 17-20, 2006

  27. Permanent change Transients 29-10-2004, 20:41 UT 17th SOT Meeting NOAJ, April 17-20, 2006

  28. Permanent change Energy release site 20:41 UT 17th SOT Meeting NOAJ, April 17-20, 2006

  29. Variations of the longitudinal component of magnetic energy DEII, erg 17th SOT Meeting NOAJ, April 17-20, 2006

  30. Two types of magnetic field changes during the impulsive phase of solar flares: • Permanent changes close the magnetic neutral line related to magnetic energy release. • Transient variations are caused by high-energy particles. • The permanent changes are consistent with shrinkage magnetic field lines across the neutral line (need vector field measurements). • Theoretical paradigm: no magnetic field changes in the photosphere. 17th SOT Meeting NOAJ, April 17-20, 2006 Kosovichev and Zharkova, 1999

  31. Energyrelease site Sub-photospheric flow maps and magnetograms during X10 flare 17th SOT Meeting NOAJ, April 17-20, 2006

  32. X17.2 flare, Oct. 28, 2003, 9:51 UT 17th SOT Meeting NOAJ, April 17-20, 2006

  33. Energy release site X17.2 flare, Oct. 28, 2003, 9:51 UT 17th SOT Meeting NOAJ, April 17-20, 2006

  34. Energyrelease site Subsurface shear flows at the energy release site 17th SOT Meeting NOAJ, April 17-20, 2006

  35. The transient variations caused by high-energy particles may generate “sunquakes” - helioseismic response to solar flares. • Sunquakes are expanding ring-like waves excited by solar flares and observed in the solar photospere. 17th SOT Meeting NOAJ, April 17-20, 2006

  36. First sunquake: July 9, 1996 17th SOT Meeting NOAJ, April 17-20, 2006 Kosovichev and Zharkova, 1998

  37. Sunquakes correlate with hard X-ray flux These observations suggest that sunquakes are excited by shock waves propagating downward from the chromosphere into the photosphere, formed by heating of the chromosphere by high-energy electrons – “thick-target” model. 17th SOT Meeting NOAJ, April 17-20, 2006

  38. Sunquakes of October 28, 2003, X17 flare 17th SOT Meeting NOAJ, April 17-20, 2006

  39. Time-distance propagation diagram of an October 28, 2003, event 17th SOT Meeting NOAJ, April 17-20, 2006

  40. Sunquake of July 16, 2004, X3.6 flare 17th SOT Meeting NOAJ, April 17-20, 2006

  41. Sunquake of January 15, 2005, X1.2 flare 17th SOT Meeting NOAJ, April 17-20, 2006

  42. X-ray, g-ray and acoustic sources of X17 flare, October 28, 2003 Doppler sources > 1 km/s Hard X-ray sources Gamma-ray sources 17th SOT Meeting NOAJ, April 17-20, 2006

  43. Strong (explicitly observed) sunquakes • July 9, 1996, X2.6 • October 28, 2003, X17 – three events • October 29, 2003, X10 • July 16, 2004, X3.6 • January 15, 2005, X1.2 • No sunquake of comparable magnitude was observed between 1996 and 2003. 17th SOT Meeting NOAJ, April 17-20, 2006

  44. Sunspot counts and X-flares during the last three solar cycles. Graphic courtesy David Hathaway, NASA/NSSTC. 17th SOT Meeting NOAJ, April 17-20, 2006

  45. Conclusions • SOT data will provide exciting unique opportunities for local helioseismology diagnostics of the subsurface structure and dynamics of the quiet Sun and active regions. • Coordinated observations with SOHO/MDI and ground-based projects (GONG, South Pole) are essential. • Substantial work (including large-scale MHD simulations of the solar convection zone) is required to improve data analysis procedures. 17th SOT Meeting NOAJ, April 17-20, 2006

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