Solar Interior & Variability (SIV)

1. Solar Interior & Variability (SIV) Peter A. Gilman High Altitude Observatory National Center for Atmospheric Research 10 October 2001

2. The SIV section focuses principally on the solar convection zone and the layers immediately below (tachocline) and above (photosphere) State of the Subject: Progress in describing and understanding these parts of the sun have been rapid, here and elsewhere Areas of focus we will talk about: • Helioseismology • Dynamos • Radiative Variability & Convection • Rising Flux Tubes & Emergence Peter A. Gilman 10 October 2001

3. Peter A. Gilman 10 October 2001

4. Recent Progress(Here & Elsewhere) Dynamos • Bulk convection zone dynamos • Interface dynamos • Flux transport dynamos • Role of meridional circulation Helioseismology • Differential rotation below photosphere • Rotation of deep interior • Meridional circulation • Torsional oscillations • Solar Cycle Sound Speed Variations • Local area helioseismology • Input for dynamos Peter A. Gilman 10 October 2001

5. Recent Progress(Here & Elsewhere) Radiative Variability & Convection • Ever improving convection simulations • Effects of partial ionization • Excitation of acoustic noise • Interactions with magnetic fields • Sunspot bright rings Rising Flux Tubes • Influence of rotation • Thin tube models  Finite tubes • 2D  3D • Flux injection at base • Flux emergence at top Peter A. Gilman 10 October 2001

6. Topics we will not focus on here, but you may want to learn more about: • Extra-Solar Planets Tim Brown • Avalanche Models for flares Paul Charbonneau • Solar Cycle Predictions from Dynamo Models Mausumi Dikpati • Meridional Flow from Helioseismology Yuhong Fan • Solar Spectrum Synthesis; The Activity-Variability Connection Peter Fox • Global MHD Instability of the Tachocline Peter Gilman • Tachocline Gravity Waves & MHD Waves Keith MacGregor • Excitation of Acoustic Waves, 3D Compressible Ionizing Convection Simulations Mark Rast • Coronal Magnetic Field Instrument Steve Tomczyk Peter A. Gilman 10 October 2001

8. Helioseismology with LOWL and ECHO Steven Tomczyk High Altitude Observatory National Center for Atmospheric Research 10 October 2001

9. ECHO Collaborators IAC* Antonio Jiménez Pere Pallé HAO Steven Tomczyk Jonathan Graham Sebastian Jiménez-Reyes Thierry Corbard *Instituto de Astrofisica de Canarias Steven Tomczyk 10 October 2001

10. LOWL MOF-based Doppler imager at Mauna Loa 2/26/94 – 9/18/00 Early science goals: Deep interior rotation, solar structure Recent goal: solar cycle variations Steven Tomczyk 10 October 2001

11. The Experiment for Coordinated HelioseismicObservations (ECHO) Network Izaña MLSO • Two station network => nearly 50% duty cycle • Improved spatial resolution, Steven Tomczyk 10 October 2001

12. ECHO Data Steven Tomczyk 10 October 2001

13. Frequency Shifts 6 years of LOWL data, 1 year averages Steven Tomczyk 10 October 2001

14. TachoclineDynamics Steven Tomczyk 10 October 2001

15. Rotation Above and Below Tachocline 0° 30° 60° • No significant variation or trend • seen in 6 x 1 year averages of LOWL Steven Tomczyk 10 October 2001

17. Flux Transport Dynamos Mausumi Dikpati High Altitude Observatory National Center for Atmospheric Research 10 October 2001

18. FLUX-TRANSPORT DYNAMO + MERIDIONAL CIRCULATION Mausumi Dikpati 10 October 2001

19. Babcock-Leighton Type Flux-Transport Dynamos Maximum meridional flow at surface Surface poloidal source Turbulent diffusivity • Equatorward migrating sunspot belts • Poleward drifting radial fields • Correct phase relationship T governed primarily by meridional flow speed Mausumi Dikpati 10 October 2001

20. Evolution of Magnetic Fields Mausumi Dikpati 10 October 2001

21. Flux-Transport Dynamos Driven By Tachocline -effect • -effect from tachocline instabilities • Also reproduces many solar cycle features • Selects correct magnetic parity (antisymmetric) for the Sun(Dikpati & Gilman, 2001, ApJ, 559, 428). Mausumi Dikpati 10 October 2001

22. Prescribed differential rotation (red contours)Meridional circulation (blue streamlines)-effect location (yellow shade) Prescribed Flows & -effect Mausumi Dikpati 10 October 2001

23. Time-Latitude Diagrams Mausumi Dikpati 10 October 2001

24. Comparison of Dynamos Poloidal fields near the surface in the Babcock-Leighton model traverse a long path to reach the equator, not able to link with other hemisphere, so instead B becomes zero there. Poloidal fields generated at the tachocline reach equator quickly, joining with their opposite hemisphere counterparts, so that Br vanishes. Surface  Tachocline  In general, both -effects should exist; tachocline-effect should be stronger, to produce correct field symmetry Mausumi Dikpati 10 October 2001

26. Fluctuations in Dynamos Paul Charbonneau High Altitude Observatory National Center for Atmospheric Research 10 October 2001

27. Time Delay in Flux Transport Dynamos Paul Charbonneau 10 October 2001

28. Dynamos As Iterative Maps Paul Charbonneau 10 October 2001

29. Amplitude Iterates from Dynamo Map Paul Charbonneau 10 October 2001

30. Dynamo Map: Paul Charbonneau 10 October 2001

31. Dynamo Intermittency • A • A • A • . Paul Charbonneau 10 October 2001

33. Solar Variability Mark P. Rast High Altitude Observatory National Center for Atmospheric Research 10 October 2001

34. The SunRISE Program • Within the US Global Change Research Program • Aimed at understanding fluctuations in the solar radiative input to the Earth’s atmosphere in order to interpret anthropological contributions to global climate changes. • At the core of the SunRISE program is a network of three Precision Telescopes • Funded by the NSF • Designed & built at NSO (Kuhn, Lin, Coulter) • Operated by • Rome Astronomical Observatory (OAR) • Mauna Loa Solar Observatory (MLSO, since March 1998) • National Solar Observatory (NSO/SacPeak) • MLSO & NSO data processed, archived, and available at: • HAO (http://rise.hao.ucar.edu) Mark P. Rast 10 October 2001

35. The PSPT • 15cm refracting telescope • Simple optical design (minimal scattered light) • Active mirror(image stabilization to ~0.25arc seconds) • High photometric precision(~0.1%) • Filters: • CaIIK line at 393.5 ± 0.12nm • Blue Continuum at 409.4 ± 0.11nm • Red Continuum at 607.1 ± 0.22nm • Detectors • 2048 x 2048 CCD camera • ~1 arc second pixels Mark P. Rast 10 October 2001

36. Irradiance Issues • What is the spectral distribution of the radiative fluctuations? (spectral synthesis project) • Coupling to terrestrial atmosphere? (TISO) • What is the relative contribution of differing magnetic structures to the radiative variability? • Are there long term global changes of the solar photosphere? (limb-darkening studies) Mark P. Rast 10 October 2001

37. Solar Physics Issues • Disentangle radiative opacity effects due to magnetic structures from convective transport modulation • Examples • Sunspot bright rings • Supergranular flows • Thermal shadows Mark P. Rast 10 October 2001

38. Sunspot Bright Rings • 0.5 – 1.0% brighter (10K warmer) than surroundings • Account for about 10% of the sunspot deficit Thermal or Magnetic? Mark P. Rast 10 October 2001

39. Masked Images(CaIIK contrast threshold here 0.125) • Bright-ring relatively insensitive to pixel selection based on CaIIK intensity • ASP observations also support dominant role for weakly magnetized Plasma ( < 50 G) • Role for very small scale structures can not be excluded. ~ Mark P. Rast 10 October 2001

40. Correlation between Kitt Peak longitudinal magnetic field measures & PSPT CaIIK intensity(with K. L. Harvey-Solar Physics Research Corporation) Mark P. Rast 10 October 2001

41. SupergranulationCan one measure the convective signature?(with HAO & SOARS summer student J. S. Sands) Mark P. Rast 10 October 2001

42. Network contributes to enhance continuum intensity • Application of network mask reveals hint of convective contribution Mark P. Rast 10 October 2001

43. Network Masks Mark P. Rast 10 October 2001

44. Network contributes to enhance continuum intensity • Application of network mask reveals hint of convective contribution Mark P. Rast 10 October 2001

46. Physics of Rising Magnetic Flux Tubes Yuhong Fan High Altitude Observatory National Center for Atmospheric Research 10 October 2001

47. Physical Questions Concerning Active Region Formation • How does toroidal magnetic field stored at the base of SCZ destabilize and form buoyant flux tubes? • How do buoyant flux tubes rise in a reasonably cohesive manner through the convection zone? • Twist • Coriolis force • Convection • How do active region flux tubes emerge through the photosphere into the solar atmosphere? 10 October 2001 Yuhong Fan

48. Destabilization of Toroidal Magnetic Field at the Base of SCZ • e.g. Cattaneo & Hughes (1988) • Cattaneo, Chiueh, & Hughes (1990) • Matthews, Hughes, & Proctor (1995) • Fan (2001) 10 October 2001 Yuhong Fan

49. Effects of Twist • Maintain cohesion of buoyantly rising flux tubes: • e.g. Longcope, Fisher, & Arendt (1996) • Moreno-Insertis & Emonet (1996) • Fan, Zweibel, & Lantz (1998) • Abbett, Fisher, & Fan (2000, 2001) • Fan (2001) • Causes a tilt (writhe) of the tube axis; Kink-unstable if the twist is sufficiently high: • e.g. Linton et al. (1996, 1998, 1999) • Fan et al. (1998, 1999) 10 October 2001 Yuhong Fan

50. Rise of Kink Unstable Magnetic Flux Tubes(Fan, Zweibel, Linton, and Fisher 1999) 10 October 2001 Yuhong Fan