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Penumbral MMFs

Penumbral MMFs. S Jaeggli (UHawaii) C Henney (NSO) S Luszcz (Cornell) S Walton (CSUN/SFO). Introduction. MMFs seen in field free photosphere sunspot moat; (Harvey & Harvey 1973)

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Penumbral MMFs

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  1. Penumbral MMFs S Jaeggli (UHawaii) C Henney (NSO) S Luszcz (Cornell) S Walton (CSUN/SFO) SPW4

  2. Introduction • MMFs seen in field free photosphere sunspot moat; (Harvey & Harvey 1973) • Evidence for penumbral moving features seen in continuum, B, inclination & velocity in single slit pointing, 2 hr ASP sequence (Lites et al 1998) • MDI data suggest only small fraction of MMFs begin inside the penumbra (Zhang, Solanki & Wang 2003) • Imaging shows outward moving features in outer half of penumbra in continuum, g-band (Bovelet & Weihr 2003) SPW4

  3. Summary • Fe 1565nm spectropolarimetric time series data in two sunspots show moving magnetic features in the mid- to outer sunspot penumbra which move outward and in some cases leave the penumbra and travel across the sunspot moat. SPW4

  4. Observations • Fe 1565nm g=3 line, IQUV, single beam, chopping about 5 s-1, about 4 sec slit step • McM/P main spectrograph, slit scanned. • CSUN/NSO IR camera 256x256 HgCdTe • 24 Jun 2002: NOAA 10008 • 26 Aug 2004: NOAA 10664 SPW4

  5. Observations SPW4

  6. Reduction • Spectral flat fields (i.e. Jones 2001) • Telescope polarization removed using the fully resolved umbral Stokes profiles of Fe line down to few 10-3. (Kuhn et al 1994) • Stokes V magnetograms: subtract blue and red wings of Stokes V • Inversion from Milne-Eddington code (Skumanich & Lites 1987) SPW4

  7. Feature with higher inclination SPW4

  8. NOAA 10008 • Elliptical penumbral region defined SPW4

  9. Stokes V “magnetogram” movie . SPW4

  10. Stokes V “magnetogram” movie . SPW4

  11. Magnetic Inclination angle movie SPW4

  12. Magnetic field strength movie . SPW4

  13. .47 km/s .22 km/s .28 km/s 1.70 km/s .38 km/s .33 km/s .64 km/s .19 km/s .33 km/s .30 km/s Radial Flow – Time Slices • Radial outflow about few tenths of km/s measured by hand SPW4

  14. Radial Flow - LCT SPW4

  15. Radial Flow - LCT SPW4

  16. Theory • A magnetic field line from the spot repeatedly threads the photosphere producing bipoles moved by moat flow (“sea-serpent” idea, Harvey & Harvey 1973) • Problems with magnetic buoyancy led Wilson (1986) to favor disconnected flux loops; Spruit, Title & van Ballegooijen (1987) suggest rising U-loops • Magnetic buoyancy can be overcome by downward convective pumping (Weiss et al 2004) SPW4

  17. Theory • A magnetic field line from the spot repeatedly threads the photosphere producing bipoles moved by moat flow (“sea-serpent” idea, Harvey & Harvey 1973) • Problems with magnetic buoyancy led Wilson (1986) to favor disconnected flux loops; Spruit, Title & Wilson (1987) suggest rising U-loops • Magnetic buoyancy can be overcome by downward convective pumping (Weiss et al 2004) SPW4

  18. Theory • Zhang Solanki & Wang (2003) suggest mass-laden Evershed flux tubes sink outside penumbra when vertical B gradient is removed. • Ryutova et al. (1994) suggest kinks can form from Evershed flow to produce traveling waves along B-field lines. • Schlichenmaier Jahn & Schmidt (1998) compute the dynamics of moving flux tubes within background field, and Schlichenmaier (2002) adds a viscosity term. SPW4

  19. SPW4

  20. First tests… • B is larger on outer footpoint • Inclination is more vertical on inner footpoint • …but plasma flow seems to be upward on outer footpoint. SPW4

  21. SPW4

  22. SPW4

  23. Summary • Penumbral MMFs are seen using IR line (confirming Lites et al 1998) and direct relationship seen with moat MMFs. • Some support for predictions from Schlichenmaier 2002, but some strange correlations too. • (More reduction and analysis needed) SPW4

  24. Feature with less inclination SPW4

  25. Radial Flow - LCT SPW4

  26. Radial Flow - LCT SPW4

  27. Stokes V “magnetogram” movie • Within the penumbra there are a few regions of opposite Stokes V, but most cases show only small differences. SPW4

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