Diagnostic capability of FG/SP
Kiyoshi Ichimoto
NAOJ
Hinode workshop, 2007.12.8-10, Beijing
Contents:- Spectral windows of SOT- Available spectral lines and their Zeeman properties- Detection limit for the magnetic field w/ polarization sensitivity of SOT- Retrievability of magnetic field from NFI observables
SOT broadband filters
Field of view 218" × 109" (full FOV)
CCD 4k × 2k pixel (full FOV), shared with the NFI
Spatial Sampling 0.0541 arcsec/pixel (full resolution)
Spectral coverage
Center (nm) Width (nm) Line of interest Purpose
388.35 0.7 CN I Magnetic network imaging
396.85 0.3 Ca II H Chromospheric heating
430.50 0.8 CH I Magnetic elements
450.45 0.4 Blue continuum Temperature
555.05 0.4 Green continuum Temperature
668.40 0.4 Red continuum Temperature
Exposure time 0.03 - 0.8 sec (typical)
BFI
BFI
BFI
Contribution function of BFI continuum
log(5000)
Response function of BFI intensity from T/Tcourtesy Dr. Mats Carlsson
CH3883, CN4305 (G-band) formation height
S. V. Berdyugina etal., 2003,A&A 412, 513–527
Quiet region
sunspot
SOT narrowband filterField of view 328"×164" (unvignetted 264"×164")
CCD 4k×2k pixel (full FOV), shared with BFI
Spatial sampling 0.08 arcsec/pixel (full resolution)
Spectral resolution 0.009nm (90mÅ) at 630nm
Spectral windows (nm) and lines of interest
Center -range Lines geff Purpose
517.2 0.6 Mg I b 517.27 1.75 Dopplergrams and magnetograms
525.0 0.6 Fe I 524.71 2.00 PhotosphericmagnetogramsFe I 525.02 3.00
Fe I 525.06 1.50
557.6 0.6 Fe I 557.61 0.00 Photospheric Dopplergrams
589.6 0.6 Na I D 589.6 1.33 Very weak fields (scattering polarization)Chromospheric fields
630.0 0.6 Fe I 630.15 1.67 Photospheric magnetograms
Fe I 630.25 2.50
Ti I 630.38 0.92 Umbral magnetograms
656.3 0.6 H I 656.28 ~1.3? Chromosphreic structure
Exposure time 0.1 - 1.6 sec (typical)
NFI 517.27 (Mg b2)
NFI 525.02
NFI 557.60
NFI 589.60 Na D1
D1D2
NFI 630.25
NFI 656.27 H
MG1 5172.680 3P1 - 3S1 2.700 -.3800WI 1259.0 b2
NA1 5895.920 2S0.5 - 2P0.5 .000 -.1840MS 564.0*
H 1 6562.740 1 2S 0.5 2P 0.5 10.199 -.0606WI 4020.0
FE1 6302.503 5P1 - 5D0 3.686 -.6100CW 83.0
FE1 5250.207 5D0 - 7D1 .121 -4.4600CW 62.0
Zeeman patterns of NFI lines
10” 100” 1000” FOV
Time res.
1”0.1”Spatial res.
1sec
1min
Time span
1hr
1day
1week
10sec
1
# of wavelength (reliability)
Random noise(detection limit)
1min
1hr
1day
10min 4
2
64
16
0.01%
0.1%
1%
0.2” 0.4”
SOT/NFIfull image Ground SP
Ground FG magnetographSOT/SP
full scan
SOT performance
Resolution for energy element ~ (x)2
SOTセミナー@花山 2004.12.7
dx=0.2”
(SOT)
dx=1”
(ground)
n = 0.5% n = 0.1% n = 0.1%
Detection limit
Bl (G) 8.5 1.7 1.7
Bt (G) 141 63 63
j (A) 1.2 x 109 5.2 x 108 2.6 x 109
(erg, l=104km) 1.3 x 1028 6.6 x 1027 1.3 x 1029
Accuracy
Bt (G, Bt=500G)
(deg., ” )
20 4 4
2.3 0.45 0.45
j (A, ” ) 1.6 x 108 3.3 x 107 3.3 x 108
erg) 2.4 x 1030
(N=1000)
4.8 x 1029
(N=1000)
1.5 x 1031
(N=500)
Detection limit and accuracy of magnetic field measurements-- rough comparison with ground-based observations --
Photon noise limited, FeI6302A line
S’ = XSX : polarimeter response matrix
Ground calibrationXr
-1S’ S”
on-boarddemodulation
SIncident Stokes vector
I’
modulatedintensity
STIncident topolarimeter
Telescope
ST = TS
S”reducedStokes vector
I”
CCDoutput
S’ SOT
product
CCD gain/darkI’’ = I’+
Polarization modulation
Measurement error: S
I’ = W ST
dark/gaincorrection
SrawSOT
raw data
Polarimeter response matrixX : true matrixXr
: matrix used in calibration
polarimeter response matrix
Sheet polarizer
window
(I,Q,U,V)
mask
FPP
Heliostat
SOT polarization calibration before launch 2005.6 @Mitaka
incidentproductV
U
Q
I
xxxx
xxxx
xxxx
xxxx
V
U
Q
I
33231303
32221202
31211101
30201000
Using well-calibrated sheet polarizers (linear & circular), the polarimeter response matrices, X, of SP and all wavelength of NFI were determined with an accuracy below.
Accuracy:
0.3333 0.3333 0.25000.0010 0.0500 0.0067 0.00500.0010 0.0067 0.0500 0.00500.0010 0.0067 0.0067 0.0500
X <
SOT is cross-talk free at ~ 10-3 level
Diagonal elements tell about the sensitivity of the SOT to Q,U,V
Left 1.0000 0.2205 0.0187 -0.0047 0.0012 0.4813 0.0652 -0.0014 0.0001 0.0513 -0.4803 -0.0057 -0.0025 0.0032 -0.0046 0.5256
Right 1.0000 -0.2112 -0.0170 -0.0051 -0.0025 -0.4875 -0.0560 0.0022 -0.0001 -0.0426 0.4907 0.0060 0.0027 -0.0008 0.0042 -0.5301
Median Mueller matrix
x matrices at scan center; CCD image each element is scaled to median + tolerance, x00 (=1) is replaced by I-image
The x matrix can be regarded as constant in the CCD.
SP
X matrix over the CCD, 517280x1024
Example of FG/NFI
left: theta= -1.571deg. 1.0000 -0.2994 -0.0336 -0.0435 0.0009 -0.4544 0.0208 0.0045 -0.0009 0.0287 0.4478 0.0068 -0.0085 0.0318 -0.0134 0.5774
right: theta= -4.441deg. 1.0000 -0.2871 -0.0305 -0.0434 -0.0003 -0.4473 0.0653 0.0038 -0.0007 0.0738 0.4435 0.0061 -0.0077 0.0310 -0.0150 0.5718
1) Detection limit for circular and linear polarizations
is the photometric accuracy x33 and x11 are diagonal elements of X
11
33
/~
/~
xQ
xV
2) Polarization signals by Zeeman effect in a weak field
)()(' TII
max//
2
max2
222
'~
'
~
d
dIBgV
d
IdBGQ
eff
3) Thus detection limit for magnetic fields are given by
Line profile convoluted with the tunable filter profile
Detection limit of NFI for weak fields
)2(0
)2(1 GGG Difference of 2nd
moments of and-components
max
222211
2
max2
33//
/'
11~
/'
11~
dIdGxB
ddIgxB
eff
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Q
U
V
SOT modulation profiles from the measured PMU retardance
Wavelength (nm)
Retardation (wave)
517.3 6.682
525.0 6.572
589.6 5.762
630.2 5.344
656.3 5.110
Wavelength
(nm) geff
G
Pol. Sensitivity(diagonal element of X)
Detection limit for B(Gauss)
V QU Bl Bt
MgI 517.2 1.75 2.88 0.577 0.452 37 970
FeI 525.0 3.00 9.00 0.266 0.609 15 210
FeI 557.6 0.00 0.00 - - - -
NaI 589.6 1.33 1.33 0.633 0.297 21 1240
FeI 630.2 2.50 6.25 0.526 0.503 10 240
HI 656.3 1.33 1.33 0.402 0.073 78 >5000
Detection limit of FG for the weak magnetic fields,
= 0.001
Line
(A)
Usage Detec. limit B
= 0.1% (G)
Bl Bt
5172 Active region lower chrom. Vector mag.fields
Shutterless mode is preferable
37 970
5250 Vector mag.field in photosphere
Highest sensitivity to linear pol. with higher spatial resolution
15 210
5576 Photospheric Dopplergram - -
5896 Longitudinal meg.field in lower chromosphere
Prominence core imaging
21 1240
6302 Vector mag.field in photosphere
Umbral mag.field with TiI line
10 240
6563 Chromosphere/prominence imaging and Dopplergram
No sensitivity to linear pol.
78 >5000
Choice of a NFI line
NFI observables -- I(i), Q(i), U(i), V(i), i = 1,,, N
Physical quantities derived from the observables -- B field strength (G),
inclination (deg.), azimuth (deg), S Doppler shift (mA)
• fill factor =1• Other quantities responsible for line formation are assumed to be those in typical quiet sun.
An algorithm to derive the magnetic field from the NFI observables is tested.The algorithm is based on the least square using model Stokes profiles calculated beforehand
How well can we retrieve the magnetic field from the products (IQUV) of the NFI?
データ解析ワークショップ 2004.12.20-23
Qpeak ( =90 ゜)
Polarization degree
Peak wavelength
I,Q,V Zeeman profiles against B
Vpeak ( =0 ゜)
I
Q
V
The method to derive the magnetic field vector from the NFI observables depends on the number of observed wavelength points.
N = 1: 1-dimensional LUT for V/I Bl, Q/I Bt individually
N = 2: Rotate the frame to make U=0 (ignore MO effect)
+ search for the best fitting to model observable in (B, , S) space
N > 3: Initial guess with cos-fit algorithm
+ rotate the frame to make U~0
+ search for the best fitting to model observable in (B, , S) sub space
To test the performance of the algorithm, numerical simulations are made using ‘artificial sample observables’ (1000 sets) calculated with an atmospheric model with random physical parameters in a range of
0 < B < 3000 G 0 < < 180 deg.-90 < < +90 deg.-90 < S < +90 mA
No Doppler info.
N = 1 at dl = -80mA, Simulation result
Sample observable, 1000pointsB < 2000G B >2000G
|S| < 60mA black blue
|S| > 60mA green red
alternative method: - ignoring MO effect - search entire (S, B, ) space
B < 2000G B >2000G
|S| < 60mA black blue
|S| > 60mA green red
N = 2 at d = [-80, 80] mA, simulation result
N = 4 at d = [-110, -70, 70,110] mA, simulation resultB < 2000G B >2000G
|S| < 60mA black blue
|S| > 60mA green redNon-uniform wavelength sampling
Diagnostics using SP data
Zeeman effect produces polarization in spectral lines
Obtain magnetic field vectors and motions in solar atmosphere.
slit
Stokes profiles fitting program
- Milen-Eddington fitting for Hinode SP Data analysis session..
- SIR fitting programs
SP data contains much more information on the structures of the solar atmosphere..