Inversions based on ME atmospheres

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Inversions based on ME atmospheres
Stokes inversions beyond ME atmospheres
Luis R. Bellot Rubio Instituto de Astrofísica de
Andalucía (CSIC) Granada, Spain
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Inversions based on ME atmospheres

• ME atmosphere
• Source function is linear with optical depth
• Absorption matrix does not vary with optical
  depth
• Analytical Stokes profiles
• Fast inversion
• Smooth maps of physical quantities
• Results are easy to interpret
• Simplistic treatment of radiation transfer
• Little thermal information. No height variations
• Cannot account for asymmetric Stokes profiles

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Asymmetric Stokes profiles

• Spatial resolution ?1"
• Advanced Stokes Polarimeter
• DST, Sac Peak
• Footpoints of cool coronal loops

Nagata, Bellot Rubio, Katsukawa (2006)
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Asymmetric Stokes profiles
Fe I 630.15 and 630.25 nm

• Spatial resolution 0.6 arcsec

• Spatial resolution ?0.7"
• POlarimetric LIttrow Spectrograph KAOS
• VTT, Observatorio del Teide
• Temporal evolution of a bipolar MMF

Cabrera Solana et al. (in preparation)
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Asymmetric Stokes profiles

• Spatial resolution ?0.4"
• KIS/IAA Visible Imaging Polarimeter TESOS
  KAOS
• VTT, Observatorio del Teide
• Pore near disk center

Bellot Rubio et al. (in preparation)
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Asymmetric Stokes profiles

• Spatial resolution ?0.2"
• TRIPPEL spectrograph AO
• Swedish 1-m Solar Telescope, La Palma
• Dark-cored penumbral filaments

Bellot Rubio, Langhans, Schlichenmaier (2005)
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ME inversions of asymmetric profiles
MHD simulations (Vögler et al. 2005)

• Fe I 630.1 and 630.2 profiles degraded to SP
  pixel size

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ME inversions of asymmetric profiles
MHD simulations (Vögler et al. 2005)

• Fe I 630.1 and 630.2 profiles degraded to SP
  pixel size
• Maps of inferred B and vLOS very similar to real
  ones!

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ME inversions of asymmetric profiles
Stokes V/I
MHD simulations (Vögler et al. 2005)
ME inv

ME inv

• Asymmetric profiles not well fitted
• ME results are some kind of average of physical
  parameters along the LOS

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The origin of asymmetries
Different magnetic atmospheres coexisting in
resolution element
Amplitude asymmetry/ Abnormal Stokes profiles
Gradients/discontinuities of physical parameters
along LOS
Area asymmetry
Auer Heasley (1978)
RF of V to B
RF of I to vLOS
RF of I to vLOS
The area asymmetry can be used to derive the
height variation of atmospheric parameters
Cabrera Solana et al. (2005)
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Available codes for inversions with gradients
SIR
Ruiz Cobo
del Toro Iniesta (1992)
1C 2C atmospheres, arbitrary stratifications,
any photospheric line
SIR/FT
Bellot Rubio et al. (1996)
Thin flux tube model, arbitrary stratifications,
any photospheric line
SIR/NLTE
Socas-Navarro et al. (1998)
NLTE line transfer, arbitrary stratifications
SIR/GAUS
Bellot Rubio (2003)
Uncombed penumbral model, arbitrary
stratifications
SPINOR
Frutiger Solanki (2001)
1C 2C atmospheres, arbitrary stratifications,
any photospheric line, molecular lines, flux tube
model, uncombed model
LILIA
Socas-Navarro (2001)
1C atmospheres, arbitrary stratifications
MISMA IC
Sánchez Almeida (1997)
MISMA model, arbitrary stratifications, any
photospheric line
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Accounting for gradients

• Inversion codes capable of dealing with gradients
• Are based on numerical solution of RTE
• Provide reliable thermal information
• Use less free parameters than ME codes (7 vs 8)
• Infer stratifications of physical parameters with
  depth
• Produce better fits to asymmetric Stokes profiles
• Height dependence of atmospheric parameters is
  needed for
• 180o azimuth disambiguation
• 3D structure of sunspots and pores
• Magnetic flux cancellation events
• Polarity inversion lines
• Dynamical state of coronal loop footpoints
• ..

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Inversions with gradients

• Spatial resolution ? 0.5"
• Intensity profiles of Fe I 557.6 nm
• Inversion SIR with 7 free parameters
• Thermal/kinematic structure of AR 0019 at
  different heights in the photosphere

Bellot Rubio, Schlichenmaier, Tritschler (2006)
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Inversions with gradients

• Spatial resolution ?0.4"
• VIP TESOS KAOS
• Inversion SIR with 10 free parameters

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Retrieving gradients from SOLAR-B/SP data
How much do gradients cost? SIR inversion with
10 free parameters Dual Xeon workstation _at_ 2.8
GHz 2 spectral lines, 136 wavelengths, 4 Stokes
parameters, model atmosphere discretized in 41
grid points
0.7 s per pixel
0.5 s per pixel
Worst-case scenario (real-time inversions)
Instrument
Pixels
Cost
Time
Workstations
SOLIS/VSM
4 x 105
3 hours?
20
50 000
POLIS
450
50 000
10 s
20
SOLAR-B/SP
1000
200 000
5 s
100
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Optimizations of SIR

• Paralellization (MPI)
• Designed for use with Linux clusters
• Speed increases linearly with number of
  processors
• Status Already available (L.Bellot)
• Porting source code to Fortran 90
• More flexibility, efficiency, and speed
• Better management of memory allocation and array
  operations
• Keep I/O to a minimum
• Status in progress (B. Ruiz Cobo)
• Use of look-up tables for spectral syntheses
• Pe as a function of T and Pg
• Absorption coefficients as functions of T and Pe
• Speed gain a factor 10-20
• Status Already available (B. Ruiz Cobo)

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Proposed strategy

• Baseline ME inversions of all SP scans
• Identify
• Pixels with bad fits and/or large asymmetries
• Regions where interesting physical processes
  occur
• Run inversions with gradients on these pixels
• Use ME results as initialization
• Not only linear stratifications, but also more
  complex height dependences will often be needed.
• Two-component model atmospheres may be required
• Critical issues
• Clarify limitations of 6301 and 6302 for quiet
  Sun magnetic field studies
• Development of efficient visualization tools