Comparison of FG and SP
data from Sun test
M. Kubo (JAXA/ISAS),
K. Ichimito, Y. Katsukawa (NAOJ),
and
SOT-team
2006/4/17-20 Extended 17th SOT meeting
Simultaneous observation with FG and SP
• We simultaneously observe a sunspot with FG SP
FG Shutterless IQUV and SP profiles (-240mÅ) (-240mÅ)
in Sun light test at NAOJ.
• Filtergraph (FG Shutterless IQUV)
- 2004/08/20 01:01:29 - 01:02:31UT
- wavelength range: Fe I 6302.5ű240mÅ
- wavelength sampling: 40mÅ step Time of
FG observation
• Spectro-polarimeter(SP) (13 wavelengths)
- 2004/08/20 00:56:19 - 01:17:46UT
(20 minutes for obtaining one map)
- spectral profile of Fe I 6302.5Å (and Fe I 6301.5Å )
- wavelength sampling (1pixel): 21.5mÅ
2006/4/17-20 Extended 17th SOT meeting 20 min
Data processing for FG and SP
1. Polarization calibration for FG and SP Stokes I
- X-matrices of FG and SP are presented (SP data)
in previous talks.
- We do not calibrate polarization induced
by optics outside SOT.
2. Determination of an absolute wavelength
of SP profiles from the telluric line (6302.0Å) Fe I 6302.5Å
(FG wavelengths are referred to fits header values.)
telluric lines
Fe I 6301.5Å
3. Convolution of SP profiles with a
transmission profile of FG Tunable Filter wavelength [pixel]
SP profiles are modified to (1pixel=21.5mÅ)
the profiles observed with FG.
4. Image co-alignment between FG - SP and
between FG images with various wavelengths
using image cross-correlation
2006/4/17-20 Extended 17th SOT meeting
Spatial distribution of IQUV at each wavelength
Stokes I
-240mÅ -120 0 +120 +240
At first, we compare FG
FG IQUV images with
SP maps at each wavelength
same as the FG images.
SP
2006/4/17-20 Extended 17th SOT meeting
Spatial distribution of IQUV at each wavelength
Stokes V
-240mÅ -120 0 +120 +240
• Line center of V profile FG
（zero-cross）for FG is
shifted about -40mÅ to the
line center of SP
(absolute wavelength).
• Stokes V images of
FG and SP have SP
similar patterns.
2006/4/17-20 Extended 17th SOT meeting
Spatial distribution of IQUV at each wavelength
Stokes Q
-240mÅ -120 0 +120 +240
Stokes Q and U FG
images of FG also
have similar patterns
of SP maps.
SP
2006/4/17-20 Extended 17th SOT meeting
Spatial distribution of IQUV at each wavelength
Stokes U
-240mÅ -120 0 +120 +240
Stokes Q and U FG
images of FG also
have similar patterns
of SP maps.
SP
2006/4/17-20 Extended 17th SOT meeting
Comparison of FG and SP profiles
• We compare FG and SP profiles for umbra, FG SP
penumbra, and quiet region. (-240mÅ) (-240mÅ)
• FG and SP profiles are averaged over the sky
blue boxes to reduce influence on image
motion due to seeing and alignment error
• Line centers of FG and SP are determined by
second-order polynomial fitting. FG profiles are
shifted to align the line centers of SP.
Stokes I umbra
◇：FG penumbra
－：SP
quiet region
alignment result
Wavelength [mÅ] 2006/4/17-20 Extended 17th SOT meeting
FG and SP profiles (penumbra)
I Q
• FG and SP IQUV profiles
are rough agreement as
a whole, but their difference
is large at some points.
• The difference of I is larger U V
than Q, U, and V. This would
be due to variation of light
level during the observation.
◇：shifted FG profile, －：SP profile
Red：normalized by red wing
Blue：normalized
2006/4/17-20 Extended 17th SOT meeting by blue wing
FG and SP profiles (quiet region)
I Q
• FG IQUV data also have
similar shapes to SP profiles
in the quiet region.
• Q, U, and V profiles of
SP and FG are well fitted U V
although degree of polarization
is very small in the quiet region.
◇：shifted FG profile, －：SP profile
Red：normalized by red wing
Blue：normalized
2006/4/17-20 Extended 17th SOT meeting by blue wing
FG and SP profiles (umbra)
I Q
• FG IQUV data also have
similar shapes to SP profiles
in the umbra.
• A scatter of FG data is larger
than that in the penumbra or
the quiet region. The umbral
profiles are easy to be affected U V
by surroundings because the
umbra is darker than the
surroundings.
• The deviation of I is large on
red-side. However the absolute
deviation is small, because the
profiles are normalized by
◇：shifted FG profile, －：SP profile
dark local continuum. Red：normalized by red wing
Blue：normalized
2006/4/17-20 Extended 17th SOT meeting by blue wing
Summary
• Stokes IQUV profiles of FG have rough agreement to
SP IQUV profiles in umbra, penumbra, and quiet region.
But their deviation is large at some points.
• The deviation of I is larger than that of Q, U, and V.
• The difference between FG and SP profiles would be due to
- false modulation signal caused by a poor seeing condition
- variation of light level
seeing condition, intensity ripple of FG tunable filter
(Removal of the intensity ripple were represented by Katsukawa-san.)
- time difference
- alignment error
2006/4/17-20 Extended 17th SOT meeting