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Penumbral MMFs

S Jaeggli (UHawaii) C Henney (NSO) S Luszcz (Cornell) S Walton (CSUN/SFO)

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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)

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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.

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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

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Observations

10008 10663

μ 0.94 0.86

Δλ (mA) 56.3 46.5

Δt (hrs) 4.5 4.5

Δs (arcsec) 0.3 x 0.9 0.1

FOV (N/S x E/W) 76 x 197 25 x 24

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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)

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Feature with higher inclination

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NOAA 10008

• Elliptical penumbral region defined

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Stokes V “magnetogram” movie

.

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Stokes V “magnetogram” movie

.

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Magnetic Inclination angle movie

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Magnetic field strength movie

.

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Radial Flow – Time Slices

• Radial outflow about few tenths of km/s measured by hand

1.70 km/s

.64 km/s

.47 km/s.22 km/s

.28 km/s

.38 km/s

.33 km/s

.19 km/s

.30 km/s

.33 km/s

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Radial Flow - LCT

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Radial Flow - LCT

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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)

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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)

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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.

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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.

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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)

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Feature with less inclination

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Radial Flow - LCT

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Radial Flow - LCT

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Stokes V “magnetogram” movie

• Within the penumbra there are a few regions of opposite Stokes V, but most cases show only small differences.