Quiet-Sun Magnetism - Probing Deep Photospheric Layers ... · Quiet-Sun Magnetism Probing Deep...
Transcript of Quiet-Sun Magnetism - Probing Deep Photospheric Layers ... · Quiet-Sun Magnetism Probing Deep...
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Quiet-Sun MagnetismProbing Deep Photospheric Layers with High Magnetic Sensitivity
Andreas Laggand the GREGOR/GRIS team1
Max-Planck-Institut fur SonnensystemforschungGottingen, Germany
1 Kiepenheuer Institut fur Sonnenphysik (KIS), Freiburg; Leibniz-Institut fur Astrophysik Potsdam (AIP); Germany
Instituto de Astrofsica de Canarias (IAC), Tenerife, Spain
Hinode-10 Meeting
NagoyaSep-05 2016
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Motivation
RelevanceQS magnetism covers>90% of solar surface(even during maxima);15% in inter-networkcrucial to understandthe solar globalmagnetisme.g. origin:local (surface) dynamoor cascade from globaldynamo?
2 / 31M. Rempel (MURaM)
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Controversial Findings Strength: few Gauss 200 Gauss kilo-Gauss?
Summary angular distributions (Tab. 2 from Steiner & Rezaei, 2012)
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1
2
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Controversial Findings Strength: few Gauss 200 Gauss kilo-Gauss?
Summary of observations
5 / 31
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Controversial Findings Strength: few Gauss 200 Gauss kilo-Gauss?
Summary of observations
5 / 31
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Reasons for Non-Conclusive Results Low B weak signals
Reason 1: Sensitivity of polarimeters
B=50G, INC=70 deg
Wavelength []
0.40.60.81.0
I
0.00100.0005
0.00000.00050.0010
Q/I C
6301.0 6301.5 6302.0 6302.5 6303.00.0040.002
0.0000.0020.004
V/I C
Fe1 Fe1Fe1 Fe1
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Reasons for Non-Conclusive Results Low B weak signals
Reason 1: Sensitivity of polarimeters
B=50G, INC=70 deg
Wavelength []
0.40.60.81.0
I
0.00100.0005
0.00000.00050.0010
Q/I C
6301.0 6301.5 6302.0 6302.5 6303.00.0040.002
0.0000.0020.004
V/I C
Fe1 Fe1Fe1 Fe1
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add noise: 103IC
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Reasons for Non-Conclusive Results Low B weak signals
Reason 1: Sensitivity of polarimeters
B=50G, INC=70 deg
Wavelength []
0.40.60.81.0
I
0.00100.0005
0.00000.00050.0010
Q/I C
6301.0 6301.5 6302.0 6302.5 6303.00.0040.002
0.0000.0020.004
V/I C
Fe1 Fe1Fe1 Fe1
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add noise: 103IC
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Reasons for Non-Conclusive Results Difference: Sensitivity to B and B||
Reason 2: Bias introduced by Zeeman effect
B=50G, INC=70 deg
Wavelength []
0.40.60.81.0
I
0.00100.0005
0.00000.00050.0010
Q/I C
6301.0 6301.5 6302.0 6302.5 6303.00.0040.002
0.0000.0020.004
V/I C
Fe1 Fe1Fe1 Fe1
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add noise: 103IC
Stenflo (2013) noise leads to more horizontal fields apparent flux: 25 higher in Bh
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Reasons for Non-Conclusive Results Cancellation & Methods
Reasons 3+4: Cancellation & Methods
Signal cancellationinsufficient spatial resolution for Zeemandiagnostics
500 km
Analysis methodsZeeman vs. Hanleselection of profiles(-level)inversions
ME vs. height dependentfilling factor
direct techniques (e.g. lineratio)
8 / 31Hinode GREGOR / Solar-C
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Reasons for Non-Conclusive Results Cancellation & Methods
Reasons 3+4: Cancellation & Methods
Signal cancellationinsufficient spatial resolution for Zeemandiagnostics
500 km
Analysis methodsZeeman vs. Hanleselection of profiles(-level)inversions
ME vs. height dependentfilling factor
direct techniques (e.g. lineratio)
8 / 31Hinode GREGOR / Solar-C
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Reasons for Non-Conclusive Results Height dependence of Bv vs. Bh
Reason 5: Height dependent Bv & Bh
Bv vs. Bhdepends strongly on
spectral line selectionanalysis method (heightdependent inversion vs. ME)heliocentric angle (higheropacity at limb)
small scale dynamo
MHD: P() sin (e.g. Vogler & Schussler, 2007)height dependent(Rempel, 2014) Rempel (2014)
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Dilemma: How to solve the controversies?
Possible solutions?
Increase spatial resolutionlarger telescope aperture
Increase signal/noise ratiomore photonsbetter polarimetermore sensitive spectral lines
Remove height biasselect lines with narrow and knownformation heightincrease height resolution
Remove model ambiguitiesselect simple, bias-free analysismethod without
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GREGOR/GRIS Observations
Recent results from GREGOR / GRIS
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GREGOR/GRIS Observations
GREGOR Infrared Spectrograph (GRIS; Collados et al., 2012)
GRIS fact sheetWL-range 12.3msensitivity < 104
/ 120 000 (@1.56m)mounted at 1.5 m GREGORtelescope0.180.30 resolution
12 / 31
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GRIS Data Fe I @ 1.56 m
Scan of quiet sun region (2015-Sep-17)
FFT rebinned:0.135 pixelsize
0.20 pixelsize(seeing limited: 0.40)
noise level reduction:4 104 IC
2.7 104 IC no loss in spatial
resolution
spectral binning
2 (oversampling)
2.1 104 IC
02468
1012
02468
1012
02468
1012
0 10 20 30 4002468
1012
0.96
0.99
1.02
1.05
Sto
kes
I
0.0020.0010.000
0.001
0.002
Sto
kes
Q
0.0020.0010.000
0.001
0.002
Sto
kes
U
0.0025
0.0000
0.0025
Sto
kes
V
x [arcsec]
y[a
rcse
c]
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2
3
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S/N Ratios Comparison to Hinode SOT/SP
Comparison: GRIS vs. SOT/SP: Stokes Maps
02468
1012
02468
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02468
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0 10 20 30 4002468
1012
0.96
0.99
1.02
1.05
Sto
kes
I
0.0020.0010.000
0.001
0.002
Sto
kes
Q
0.0020.0010.000
0.001
0.002
Sto
kes
U
0.0025
0.0000
0.0025
Sto
kes
V
x [arcsec]
y[a
rcse
c]
02468
1012
02468
1012
02468
1012
0 10 20 30 4002468
1012
0.88
0.96
1.04
1.12
Sto
kes
I
0.0025
0.0000
0.0025
Sto
kes
Q
0.0025
0.0000
0.0025
Sto
kes
U
0.005
0.000
0.005
Sto
kes
V
x [arcsec]
y[a
rcse
c]
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GREGOR/[email protected], 0.40 Hinode SOT/SP (deep 12.8s)
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S/N Ratios Comparison to Hinode SOT/SP
Comparison: GRIS vs. SOT/SP: LP/CP Coverage
0
2
4
6
8
10
12
0 10 20 30 400
2
4
6
8
10
12
x [arcsec]
y[a
rcse
c]
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V
3Q,U
3Q,U,V
3
GR
EG
OR
/GR
IS4.
8s,
0. 4
0,21
04
Hin
ode
SO
T/S
P12
.8s,
0. 4
0,71
04
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S/N Ratios Comparison to Hinode SOT/SP
Stokes signal levels
Comparison GRIS Hinode SOT/SP
- GRIS [%] LP LP SOT/SP [%] LP LPlevel and or and or
LP CP CP CP LP CP CP CP3 39.7 73.0 33.1 79.7 9.8 49.3 7.7 51.44 18.4 57.0 13.9 61.5 4.2 37.1 3.1 38.25 9.2 44.2 6.2 47.2 2.1 28.5 1.5 29.1
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Magnetic Line Ratios (MLRs) The principle
Simple diagnostic techniques: MLR - field strength
Magnetic Line Ratio (Solanki et al., 1992)
MLR =geff(15652)Vmax(15648)g(15648)Vmax(15652)
Requirements:spectral lines identical except for Lande factor2 distinct components:(1) magnetized, (2) field-freesmall gradients in log
not fulfilled for Fe I 1.56 line pair
BUT: similar formation height, narrowformation height range, similar thermalproperties
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Magnetic Line Ratios (MLRs) The principle
Simple diagnostic techniques: MLR - field strength
Magnetic Line Ratio (Solanki et al., 1992)
MLR =geff(15652)Vmax(15648)g(15648)Vmax(15652)
Requirements:spectral lines identical except for Lande factor2 distinct components:(1) magnetized, (2) field-freesmall gradients in log
not fulfilled for Fe I 1.56 line pair
BUT: similar formation height, narrowformation height range, similar thermalproperties
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Magnetic Line Ratios (MLRs) The principle
Simple diagnostic techniques: MLR - field strength
Magnetic Line Ratio (Solanki et al., 1992)
MLR =geff(15652)Vmax(15648)g(15648)Vmax(15652)
Requirements:spectral lines identical except for Lande factor2 distinct components:(1) magnetized, (2) field-freesmall gradients in log
not fulfilled for Fe I 1.56 line pair BUT: similar formation height, narrow
formation height range, similar thermalproperties
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Magnetic Line Ratios (MLRs) Profile selection
MLR analysis - select normal profiles
Stok
es V
noise threshold 3 small amplitude asym. a small area asym. A
(43.7% of the profiles)
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Magnetic Line Ratios (MLRs) Profile selection
MLR analysis - select normal profiles
Stok
es V
noise threshold 3
small amplitude asym. a small area asym. A
(43.7% of the profiles)
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Magnetic Line Ratios (MLRs) Profile selection
MLR analysis - select normal profiles
Stok
es V
noise threshold 3 small amplitude asym. a
small area asym. A
(43.7% of the profiles)
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Magnetic Line Ratios (MLRs) Profile selection
MLR analysis - select normal profiles
Stok
es V
noise threshold 3 small amplitude asym. a small area asym. A
(43.7% of the profiles)
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Magnetic Line Ratios (MLRs) Profile selection
MLR analysis - select normal profiles
Stok
es V
noise threshold 3 small amplitude asym. a small area asym. A
(43.7% of the profiles)18 / 31
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Magnetic Line Ratios (MLRs) Profile selection
Stokes Profiles: Red: MLR0.6, large Vmax, Yellow 3: MLR0.6, small Vmax
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yellow: V 3
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Magnetic Line Ratios (MLRs) Profile selection
Stokes Profiles: Red: MLR0.6, large Vmax, Yellow 3: MLR0.6, small Vmax
MLR ~ 0.6
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yellow: V 3
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Magnetic Line Ratios (MLRs) MLRs for Fe I 15648 / Fe I 15652
MLR Fe I 15648 / Fe I 15652
0.002 0.004 0.006 0.008 0.010 0.012 0.014Vmax(15648.5)
0123probability density [%]
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.01.
53V
max
(156
48.5
)/3.
00V
max
(156
52.9
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
prob
abili
tyde
nsity
[%]
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Magnetic Line Ratios (MLRs) MLRs for Fe I 15648 / Fe I 15652
Different MLR regions
0.002 0.004 0.006 0.008 0.010 0.012 0.014Vmax(15648.5)
3.0
0123probability density [%]
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.01.
53V
max
(156
48.5
)/3.
00V
max
(156
52.9
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
prob
abili
tyde
nsity
[%]
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2
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Magnetic Line Ratios (MLRs) MLRs for Fe I 15648 / Fe I 15652
Different MLR regions
0.002 0.004 0.006 0.008 0.010 0.012 0.014Vmax(15648.5)
3.0
0123probability density [%]
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.01.
53V
max
(156
48.5
)/3.
00V
max
(156
52.9
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
prob
abili
tyde
nsity
[%]
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Blue Region:MLR1.2, small Vmax
Yellow Region:MLR0.6, small Vmax
Green Region:MLR1.2, large Vmax
Red Region:MLR0.6, large Vmax
1
2
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Magnetic Line Ratios (MLRs) MLRs for Fe I 15648 / Fe I 15652
Different MLR regions
0.002 0.004 0.006 0.008 0.010 0.012 0.014Vmax(15648.5)
3.0
0123probability density [%]
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.01.
53V
max
(156
48.5
)/3.
00V
max
(156
52.9
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
prob
abili
tyde
nsity
[%]
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Blue Region:MLR1.2, small Vmax
Yellow Region:MLR0.6, small Vmax
Green Region:MLR1.2, large Vmax
Red Region:MLR0.6, large Vmax
1
2
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Magnetic Line Ratios (MLRs) MLRs for Fe I 15648 / Fe I 15652
Different MLR regions
0.002 0.004 0.006 0.008 0.010 0.012 0.014Vmax(15648.5)
3.0
0123probability density [%]
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.01.
53V
max
(156
48.5
)/3.
00V
max
(156
52.9
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
prob
abili
tyde
nsity
[%]
21 / 31
Blue Region:MLR1.2, small Vmax
Yellow Region:MLR0.6, small Vmax
Green Region:MLR1.2, large Vmax
Red Region:MLR0.6, large Vmax
1
2
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Magnetic Line Ratios (MLRs) MLRs for Fe I 15648 / Fe I 15652
Different MLR regions - Where?
0 10 20 30 40 5002468
1012
y[a
rcse
c]
0 10 20 30 40 50x [arcsec]
02468
1012
y[a
rcse
c]
0.940.960.981.001.021.041.06
I c
0.00450.00300.00150.00000.00150.00300.0045
V
0 10 20 30 4002468
1012
0.96
0.99
1.02
1.05
Sto
kes
I
x [arcsec]
y[a
rcse
c]
22 / 31MLR1.2, small Vmax (hG) MLR1.2, large Vmax (hG) MLR0.6, small Vmax (kG) MLR0.6, large Vmax (kG)
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Magnetic Line Ratios (MLRs) MLRs for Fe I 15648 / Fe I 15652
Different MLR regions - Where?
0 10 20 30 40 5002468
1012
y[a
rcse
c]
0 10 20 30 40 50x [arcsec]
02468
1012
y[a
rcse
c]
0.940.960.981.001.021.041.06
I c
0.00450.00300.00150.00000.00150.00300.0045
V
0 10 20 30 4002468
1012
0.96
0.99
1.02
1.05
Sto
kes
I
x [arcsec]
y[a
rcse
c]
22 / 31MLR1.2, small Vmax (hG) MLR1.2, large Vmax (hG) MLR0.6, small Vmax (kG) MLR0.6, large Vmax (kG)MLR1.2, small Vmax (hG) MLR1.2, large Vmax (hG) MLR0.6, small Vmax (kG) MLR0.6, large Vmax (kG)
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Magnetic Line Ratios (MLRs) MLRs for Fe I 15648 / Fe I 15652
Different MLR regions - Where?
0 10 20 30 40 5002468
1012
y[a
rcse
c]
0 10 20 30 40 50x [arcsec]
02468
1012
y[a
rcse
c]
0.940.960.981.001.021.041.06
I c
0.00450.00300.00150.00000.00150.00300.0045
V
0 10 20 30 4002468
1012
0.96
0.99
1.02
1.05
Sto
kes
I
x [arcsec]
y[a
rcse
c]
22 / 31MLR1.2, small Vmax (hG) MLR1.2, large Vmax (hG) MLR0.6, small Vmax (kG) MLR0.6, large Vmax (kG)MLR1.2, small Vmax (hG) MLR1.2, large Vmax (hG) MLR0.6, small Vmax (kG) MLR0.6, large Vmax (kG)
some kG patches (red); surrounded by yellow halo; ubiquitous weak fields (green & blue)
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MHD-Simulation Comparison Small scale dynamo run & IMaX run
Test using MHD Quiet Sun simulations (SSD+IMaX run)
23 / 31
0 5 10 15 200
5
10
15
0 5 10 15 200
5
10
15
0.88
0.96
1.04
1.12
Sto
kes
I
0
400
800
1200
mag
netic
field
stre
ngth
[G]
log
=(
0.2,0.8
)
x [arcsec]
y[a
rcse
c]
MHD simulations: SSD+IMaX runRempel (2014): O16bMRiethmuller et al. (2016)
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MHD-Simulation Comparison Small scale dynamo run & IMaX run
Test using MHD Quiet Sun simulations (SSD+IMaX run)
23 / 31
0 5 10 15 200
5
10
15
0 5 10 15 200
5
10
15
0.96
0.99
1.02
1.05
Sto
kes
I
0
400
800
1200
mag
netic
field
stre
ngth
[G]
log
=(
0.2,0.8
)
x [arcsec]
y[a
rcse
c]
spatial degrading
GREGOR-PSF + 0.25 Gaussian +Lorentzian wings
match contrast, resolution, Ic histogram
spectral degrading
12% straylight
150 mA Gauss
MLR1.2, small Vmax (hG) MLR1.2, large Vmax (hG) MLR0.6, small Vmax (kG) MLR0.6, large Vmax (kG)
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MHD-Simulation Comparison Small scale dynamo run & IMaX run
MLR (SSD + IMaX run, degraded)
0.002 0.004 0.006 0.008 0.010 0.012 0.014Vmax(15648.5)
3.0
0123probability density [%]
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.01.
53V
max
(156
48.5
)/3.
00V
max
(156
52.9
)
0
500
1000
1500
2000
mag
netic
field
stre
ngth
[G]
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MHD-Simulation Comparison Small scale dynamo run & IMaX run
MLR (SSD + IMaX run, degraded)
0.002 0.004 0.006 0.008 0.010 0.012 0.014Vmax(15648.5)
3.0
0123probability density [%]
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.01.
53V
max
(156
48.5
)/3.
00V
max
(156
52.9
)
0
500
1000
1500
2000
mag
netic
field
stre
ngth
[G]
24 / 31
Blue Region:MLR1.2, small Vmax
Yellow Region:MLR0.6, small Vmax
Green Region:MLR1.2, large Vmax
Red Region:MLR0.6, large Vmax
1
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MHD-Simulation Comparison Small scale dynamo run & IMaX run
B strength (SSD + IMaX run)
0 500 1000 1500 2000 2500magnetic field strength [G]
100
101
102pr
obab
ility
dens
ity[%
]
0.40MLR 0.850.90MLR 1.60
25 / 31
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LP/CP ratio The principle
Simple diagnostic techniques: LP/CP - inclination
LP/CP ratio (Solanki et al.,1992)
LP/CP =
Q2max + U2max
Vmax
1 depends only on ifB sufficiently strong( 1 kG)small gradients
2 depends on and B forweaker fields
0.7
0.8
0.9
1.0
I
0.001
0.000
0.001
Q
0.001
0.000
0.001
U
15650 15655 15660 15665
wavelength []
0.020.01
0.00
0.01
0.02
V
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LP/CP ratio LP/CP for Fe I 15648
GRIS: LP/CP for Fe I 15648
0.002 0.004 0.006 0.008 0.010 0.012 0.014Vmax(15648.5)
0246probability density [%]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Q
2+
U2 /
V(1
5648
.5)
0.0
0.1
0.2
0.3
0.4
0.5
prob
abili
tyde
nsity
[%]
27 / 31
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LP/CP ratio LP/CP for Fe I 15648
MHD (SSD+IMaX, degraded): LP/CP for Fe I 15648
0.002 0.004 0.006 0.008 0.010 0.012 0.014Vmax(15648.5)
02468probability density [%]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Q
2+
U2 /
V(1
5648
.5)
0
20
40
60
80
mag
netic
field
incl
inat
ion
[]
28 / 31
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LP/CP ratio LP/CP for Fe I 15648
B inclination (SSD + IMaX run)
0 20 40 60 80 100 120 140 160 180inclination angle []
0
2
4
6
8
10
12
14pr
obab
ility
dens
ity[%
]
0.40MLR 0.850.90MLR 1.60isotropic
sin()3.22
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Summary
Summary: Quiet Sun Stokes Profiles
Noise Statistics: GRISHinodenoise level 2.1 104 0.40)TP: 80% above 3(cf. Hinode 12.8 s scan:51%)CP: 73% above 3(cf. Hinode 12.8 s scan:49%)LP: 40% above 3(cf. Hinode 12.8 s scan:10%)
more reliable inversions arenow possible
MLR & LP/CP ratio
some kG patches resolved (vertical fields)PSF-ring around kG patcheshG patches ubiquitousgood agreement with SSD runs some kG patches missing
Proper PSF deconvolution critical for correctinterpretation of results!
Future instrumental improvementsGREGOR/GRIS: reach diffraction limitSunrise III: increase height resolution
30 / 31
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Summary
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MotivationControversial FindingsStrength: few Gauss 200 Gauss kilo-Gauss?
Reasons for Non-Conclusive ResultsLow B weak signalsDifference: Sensitivity to B and B||Cancellation & MethodsHeight dependence of Bv vs. Bh
Dilemma: How to solve the controversies?GREGOR/GRIS ObservationsGRIS DataFei @ 1.56 m
S/N RatiosComparison to Hinode SOT/SP
Magnetic Line Ratios (MLRs)The principleProfile selectionMLRs for Fei 15648 / Fei 15652
MHD-Simulation ComparisonSmall scale dynamo run & IMaX run
LP/CP ratioThe principleLP/CP for Fei 15648
Summary
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