宇宙からの次世代	  彩層磁場観測	
石川遼子（国立天文台）	

Advantages of space-based obs. 	
• UV range– Impossible to access from the ground• Blue side of the spectrum– Adaptive optics system does not work
– Higher diﬀraction limit than that in red & IR

• Capable of long exposure (high polarizationsensitivity) keeping the high spatial resolution– Lessons learned from Hinode/SP	Requirements to spectral lines	• Emitted from low β region• Enable to observe the vector magnetic field– Magnetic fields are inclined in the chromosphere• Sensitive to less than 10 G for vector field– Transient granular-size horizontal fields: Bphot=400G@ photosphere (Ishikawa et al. 2008)– @ upper chromosphere [h=2000km ~ 8 Hp]
Pchro ~ exp(-8)Pphot ⇒ Bchro ~ exp(-4)Bphot ~7G(420km)
-3.0

350

t=0	

t=120s	-2.0log τfield strength (G)-2.5?	

-1.5
-1.0
-0.5

0

0.0

600km

1320kmIshikawa et al. (2010)	

Limitation of Zeeman eﬀect	
• Hard to achieve high sensitivity to transverse
magnetic field!V $Polarization sensitivity of 10-3
Blong = 4348 # &" I %1gives at FeI 6302A• Blong = 4G & Btran = 100G	! Q $2
Btran = 3371# &" I % Landi Degl’Innocenti & Landolfi (2004)	

• Very weak signals because of large Doppler
broadening in the chromosphere and aboveΔωΒ	ν	ΔωΒ	Atomic polarization	
• Population imbalance between magnetic sublevels
induced by anisotropic radiation• Quantum coherency by rotation of quantization axes	τ	Anisotropic radiation
m=-1	

m=0	

m=+1	

J=1	

Uniform radiation
m=-1	

m=0	

m=+1	

J=1	

No population imbalance,
no atomic polarization!	

Hanle eﬀect	
• Magnetic fields dephase & decrease
coherenceeOperates at ωB~A	

ωB =gB : Larmor frequency	

2m
A : Einstein coeﬃcient	

Large A (Lya, MgII k, ….)→ Large BH
Small A (e.g., forbidden line) → Small BH	
Q/I @ Lya	

local normal	μ=0.3	

θB=90°	χB=120°	

U/I @ Lya	

Inversion of Hanle eﬀect	
σ = 0.033%
μ = 0.3

field
strength B
Field
strength
[G]	

250
200
150
100
50
0300hut
imaz

200

χB100

• Hanle eﬀect only does
not allow to uniquelydetermine the threecomponents ofmagnetic field.
• Additional information(Stokes V fromZeeman, simultaneousHanle measurement
150with other line,….) is100 θθ B	 required.	
n50 clinatiotionin na
B0 0IncliIshikawa et al. (2014)	

Diagnostics sample different heights

Formation Height	
Adopted from presentation by Carlsson in SOLAR-C science meeting 2013 	
Gray scale: HeI	CaII 8542 (triplet) << HeI ~ CaII h(k) < MgII h(k)β~1β<<1• HeI is observed everywhere in QS???? Other candidates are MgII
k and CaII k.	
Pressure scale height : 500km @ 104 K	Mg
IIk	The longitudinal Zeeman effect

Scattering polarization

Adopted from presentation by Belluzzi in SOLAR-C science meeting 2012 	kSimilar
amplitudesof scattering• Up to now, there is no observationof atomicpolarizationin polarizatio
this line. However, the atomic system and the line formation
The amplitudes of the circular polarization
signals producedby the Zeeman
2P2P
3/2
3/2
are samesimilar
to hydrogen
Lyα, and CLASP observation ineffectheightare of theorderof magnitude.
85
422015 will greatly help us to understandthisline!	
2P2P
841/21/298 and b).
Note the strong V/I signals produced by the subordinate Mg II lines(a8662D5

Ca II k	4

StenfloStenflo (2004)	

Figure 3.

Stokes spectra around the core of the Ca ii K line for the quiet Sun

Candidates of spectral lines for SUVIT+ sensitive toVer.Hanle	
2014.10.14	
UPPER CHROMOSPHERIC LINES ONLY!	
Spectral line(A)�1.22/D Response height[km]� Zeeman eﬀect�[arcsec]�
Te�V�
Blong[G]� Btran[G]�

Hanle eﬀect�Range[G]�

P [%]�

HeII 304�

-�Transition region�-�-�85 - 850�

1.5	

Lyα 1216�

-�Transition region�-�-�

0.5 - 50�

0.5	MgII k 2796�

0.046�

1300�

1400�

130�

2100�

0.3 - 25�

1.5	CaII k 3933�

0.065�

1000�

1200�

81�

1700�

0.2 - 15�

1.5	

HI β 4861�

0.080�

1500�

1000�

19�

1300�

HI α 4861�

0.108�

1500�

1300�

9.9�

910�

Collisional
depolarization??�

CaII 8498�

0.140�

700�

1000�

5.6�

280�

10-3 - 10�

CaII 8542�

0.141�

800�

1200�

6.1�

330�

CaII 8662�

0.143�

700�

1000�

7.6�

410�

HeI 10830 (QS)�

0.179�

1800�

1800�

20�400�

HeI 10830 (AR)�

0.179�

1800�

1800�

10�280�

10-3 – 10-2�
Blue:10-2-10-1
Red: 10-1-1�

0.01	
0.4	
0.4	
Blue:0.03
Red:0.15	

Information of the Hanle eﬀect is added to the updated table in MPD. 	

Trade-Oﬀ	
Zeeman sensitivity�

Hanle eﬀect�Formationheight�Blong�

Btran�

Sensitive
B range�

Atomicpol.�

Lyα 1216 �◎�

×	×	◯�

MgII k 2796A�

◯�

△	×	

CaII k 3933A�◯�△	

CaII 8498A�

×	CaII 8542A�

Spectral line�

Interpretation�
Atmos.
model�3Deﬀect�

△	△?	

△?	

◯�◯�△?	

△?	

×	◯�◯�

△?	

△?	

◯�×	△	×	△?	

△?	

×	◯�

×	△	△?	

△?	

CaII 8662A�

×	◯�

×	△	△?	

△?	

HeI 10830A (QS)�

◯�

×?�

×	

HeI 10830A (AR)�

◯�

◯�

×	△	

◯?	

◯?	

×	×	

Summary	• It may be risky to rely on the HeI 10830 since it
is not visible everywhere in the quiet Sun(especially in the internetwork region).
• Alternative plan is the spectro-polarimetricobservations in CaII k and MgII k. These are newgeneration of space-based observations (CLASP,CLASP+, small satellite mission….)!
• For the SUVIT line selection, the trade oﬀ isnecessary.
– Organize an international task force.