SOLAR FLARE OPTICAL SPECTROPOLARIMETRY

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SOLAR FLARE OPTICAL SPECTROPOLARIMETRY
Zhi XU (1,2), Jean-Claude HENOUX (1), Gilbert
CHAMBE (1), Alexander PETRESHEN (3) and Cheng
FANG (4) (1) OBSERVATOIRE DE PARIS, LESIA,
France (2) YUNNAN OBSERVATORY, China (3) St
PETERSBURG INSTITUTE OF OPTICS, Russia (4)
NANJING UNIVERSITY, China
Xu et al. 2005, ApJ, 631, 618 Xu et al. 2006,
ApJ submitted
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THEMIS OBSERVATIONS
June 15th 2001 Flare
Hard X-rays
HXRS 29 44 keV 44 67 keV
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2D distributions of Ha (left) and Hb (right)
polarization (at 1007 UT), and of the
longitudinal magnetic field B//.
P radial
P tangential
P radial
Hb
Ha
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2D distribution of Ha, Hb and Mg I 552.84
nm line linear polarization at 1007 UT
Polarization Radial triangles Tangential
stars Ha (blue) Hb (green) Mg I
(red) Line-center intensity contours Ha
(dotted line) - - - - - MgI (solid line) 0.42
arc second square/pixel
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Time variation of Mg I line impact polarization

• 10 pixels averaged
• intensity (triangles)
• - polarization degree (stars)
• from 1007 to 1012 UT.

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• CONCLUSIONS
• The Ha, Hb and Mg lines are linearly polarized.
• The highest polarization is observed at flare
  kernels borders.
• Radial linear polarization is present in Ha, Hb
  and Mg lines.
• Tangential linear polarization in Ha is also
  present .
• Both return current electrons associated with
  electron beams and low energy protons can explain
  the readial polarization observed.