NourEddine Raouafi

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Magnetic and Velocity Fields in the Solar Corona
Nour-Eddine Raouafi
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Area of interest polar coronal holes

• Open superradial expanding field lines
• Source of the fast solar wind

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(No Transcript)
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UVCS Results
Very broad line profiles emitted by heavy ions (O
VI, Mg X) in the polar coronal holes
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Interpretation of UVCS observations
Wave-particle energy exchange at cyclotron
frequencies of the solar wind species
High anisotropies in the velocity
distributions of the scattering atoms
Impact on the mechanisms of acceleration
heating of the coronal plasma
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Atmospheric parameters electron density
DKL
Guhathakurta Holzer (1994) Guhathakurta et al.
(1999) Cranmer et al. (1999) Esser et al.
(1999) power series
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O VI Total Intensities
The observed intensities are reasonably
reproduced by most of the density models (DKL,
GH94, Cra99) Guh99 Ess99 give relatively low
intensities at low altitudes
(Raouafi Solanki, 2004b)
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O VI Widths Intensity Ratios

• The LOS-integrated profiles are very sensitive
  to the density stratification details
• DKL density stratification gives line widths
  comparable to the observed ones
• The calculated intensity
• ratios are relatively close to
• the observed ones
• (except for Guh99 Ess99)

(Raouafi Solanki, 2004a,b)
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SUMER The Polarimeter
N.-E. Raouafi P. LEMAIRE S. Sahal-Brechot
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The SOlar Heliospheric Observatory (SOHO)
mission

• ? Three-axis stabilized
• ? Capacity of rolling
• around z-axis
• Objectives
• ... Coronal heating
• Sources acceleration
• of the solar wind
• (CDS, UVCS, EIT, LASCO SUMER)

The Solar Ultraviolet Measurements of Emitted
Radiation
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SUMERs Optical Design
?Sensitivity to the polarization
? Capability of rastering
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Observations

• Date
• SoHO roll of
• March 19, 1996
• Target
• An area in the polar
• coronal hole at 1.3 R?
• Goal
• Observe this area
• angles with respect
• to the polar axis

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Wavelength range 1022 1042 Å
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Results
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Results
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Interpretation of the observations
Polarization measurements Quantum theory of
matter-radiation interaction (Raouafi 2002)

• Constraints on the
• ? Coronal magnetic field Hanle effect (lt 3
  Gauss)
• ? Solar wind velocity vector Doppler
  redistribution
• (40 70 km s-1)
  (Raouafi et al. 2002a,b)

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Conclusion SUMER showed us the way to infer
the coronal magnetic field the solar
wind velocity vectors through the Hanle
effect and the Doppler redistribution.
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Thanks Philippe