I’m R. Kano from NAOJ. I would like to show the CLASP ... · Lyman-αscattering polarization...

Lyman-α scattering polarization observed with the Chromospheric Lyman-Alpha

Spectro-Polarimeter (CLASP)R. Kano (NAOJ)1, J. Trujillo Bueno2,3,4, A. Winebarger5, F. Auchère6, N. Narukage1, R. Ishikawa1, K. Kobayashi5

& CLASP team6,7,8,9,10,11,12,13,14,15,16

1 NAOJ, 2 IAC, 3 ULL, 4 CSIC, 5 NASA/MSFC, 6 IAS, 7 ISAS/JAXA, 8 SOKENDAI, 9 Kyoto Univ, 10 NIFS, 11 IRSOL, 12 ASCR, 13 MPS, 14 LMSAL, 15 HAO, 16 Univ. of Oslo

https://ntrs.nasa.gov/search.jsp?R=20160011526 2020-01-03T18:56:10+00:00Z

プレゼンター

プレゼンテーションのノート

I’m R. Kano from NAOJ. I would like to show the CLASP results as well as the project. CLASP is an international experiment between Japan, USA, and Europe, to use …

2

Chromospheric Lyman-Alpha Spectro-Polarimeter

• High-precision (<0.1%) spectro-polarimetry in VUV.

• First detection of scatteringpolarization in the Lyα line (121.6 nm).

• Exploration of magnetic fields in the upper chromosphere and the transition region via the Hanle effect.

2016/09/15 CLASP in SPW8

プレゼンター


the NASA sounding rocket. The aim is to make “High- …”, and to make the “First …”. Then finally, we would like to explore “magnetic fields …”. This talk covers these two. For the 3rd topic, please wait Ishikawa’s talk in this afternoon.

Why Lyα line?

• Brightest line in VUV chromospheric emission lines, and bright even in quiet Sun as well as active regions.

• Line core is emitted by the plasma located between upper chromosphere and transition region (TR).

• Good sensitivity to magnetic field of 10 – 100 G via Hanle effect. Lyα line is a suitable candidate to constrain magnetic fields and the

geometrical complexity of the low-β TR plasma over the entire solar disk.

Lyα121.567nm

Transition region (TR)Lyα coreLyα wing

Gary (2001) Vernazza et al. (1981)

Solar spectrum in VUV range Plasma-β and formation height of Lyα in the solar atmosphere

Corona

Chromosphere

Photosphere

Temperature (K)

Heig

ht (k

m)

2016/09/15 CLASP in SPW8 3

プレゼンター


Fineschi san showed the Lya line as a lower chromospheric line. It may true for the wing but not true for the core. The Lya line core is formed between upper chromosphere and transition region. Of course, it is brightest in VUV, and bright anywhere on the Sun. And then, it is sensitive to magnetic field of 10-100G via Hanle effect. Therefore, we think “Lya line …” even for the disk observation.

Polarization in Lyα line

Line core: • Scattering polarization

+ Hanle effect• sensitive to 10 - 100 G

Line wing: • Scattering polarization• sensitive to

temperature structure

2016/09/15 CLASP in SPW8 4Trujillo Bueno et al. (2011) Belluzzi et al. (2012)

プレゼンター


However, only the line core is sensitive to the Hanle effect. And the polarization in the core was expected smaller than 1 % as shown here, while a few percent in the wings was expected as shown here. Therefore, at least 0.1% of the polarization sensitivity is required to infer magnetic fields.

CLASP Instrument

• Two symmetric channels: Ch1 & Ch2▶ Simultaneously measure orthogonal polarization states

• Realize high throughput in VUV◀ Minimize the number of optical components◀ Apply high-reflectivity coating to all optical components

Cassegrain telescope Slitjaw Optics Spectro-Polarimeter

Constant-line-spacing spherical grating

slit

rotatingwaveplate

CCD cameras

Polarization analyzer

-1st order

+1st order

Ch1

Ch2Aperture heat absorber

Narukage et al. (2015, Applied Optics)

Off-axis parabola

2016/09/15 CLASP in SPW8 5

プレゼンター


To achieve such high sensitivity, the CLASP instrument has two identical channels, which measure the orthogonal polarizations simultaneously, and minimize the error caused by the intensity chang.

2016/09/15 CLASP in SPW8 6

Cassegrain telescope Slitjaw Optics Spectro-Polarimeter

Constant-line-spacing spherical grating

slit

rotatingwaveplate

CCD cameras

Polarization analyzer

-1st order

+1st order

Ch1

Ch2Aperture heat absorber

Slitjaw Optics

Wavelength 121.567 nm (NB filter)

Plate scale 1.03’’/pixel

FoV 527’’×527’’

Cassegrain Telescope

Aperture φ270.0 mm

Focal Length 2614 mm (F/9.68)

Visible light rejection

“Cold Mirror” coating on primary mirror

CLASP Instrument

Off-axis parabola

Narukage et al. (2015, Applied Optics)

Spectro-Polarimeter

Optics Inverse Wadsworth mounting

Wavelength 121.567 ± 0.61 nm

Slit 1.45’’ (width), 400’’ (length)

Grating Spherical constant-line-spacing, 3000/mm

CCD camera 512×512 pixel 13μm/pixel

Plate scale 0.0048 nm/pixel 1.11’’/pixel

Resolution 0.01nm 3’’

Sensitivity 0.1%

プレゼンター


There are two focal plane sub-instruments. One is SJ to take Lya filter images every 0.6s, and the other is SP to take Lya spectra with 0.01nm resolution and its polarization with 0.1% sensitivity.

2016/09/15 CLASP in SPW8 7

CLASP InstrumentNarukage et al. (2015, Applied Optics)

Slitjaw Optics

Wavelength 121.567 nm (NB filter)

Plate scale 1.03’’/pixel

FoV 527’’×527’’

Cassegrain Telescope

Aperture φ270.0 mm

Focal Length 2614 mm (F/9.68)

Visible light rejection

“Cold Mirror” coating on primary mirror

Spectro-Polarimeter

Optics Inverse Wadsworth mounting

Wavelength 121.567 ± 0.61 nm

Slit 1.45’’ (width), 400’’ (length)

Grating Spherical constant-line-spacing, 3000/mm

CCD camera 512×512 pixel 13μm/pixel

Plate scale 0.0048 nm/pixel 1.11’’/pixel

Resolution 0.01nm 3’’

Sensitivity 0.1%

プレゼンター


The flight instrument was developed like this.

2016/09/15 CLASP in SPW8 8

Modulation & Demodulation• CLASP is optimized for linear polarization, because V/I due to Zeeman is

expected to be too small (~0.005% @10G in the Lyman-α by Zeeman effect).

time

½Iunpol

Ipol

by rotating WP detected by CCDD1 D2

D4D3

I

Q = aK{(D1 – D2 – D3 + D4) + …}

= K{(D1 + D2 + D3 + D4) + …}

= aK{(D2 – D3 – D4 + D5) + …}U

a: modulation coefficientK: throughput value

Reflective Polarization Analyzer

Rotating Half-Waveplate

(4.8 s/rot)

Un-pol. Comp.

Pol. Comp.

incident Lyα light

Iunpol

Ipol

68˚

principal axes

CLASP Polarimeter

Demodulationfrom CCD exposures

time

Modulation

+Q

–Q

–U+U

プレゼンター


In this instrument, a half-waveplate rotates continuously at 4.8s/rot. It rotates the direction of the incident linear polarization, and then a reflective polarization analyzer in each channel extract each component of the linear polarizations. Because V/I …, CLASP is optimized …. CCD camera takes 4 exposures in one modulation, and then we can derive the Stokes IQU by these demodulation formula. The reflective polarization analyzer in CLASP is a multilayer-coating one based on Brido et al. and developed with Acton Optics. IMG_0970.MOV

2016/09/15 CLASP in SPW8 9

SP polarization calibrationWe performed the polarization calibration only to SP, because the instrument polarization in the telescope is negligibly small.

+Q–Q+U –U

• Rotate entire light source• Rotate ½ waveplate2 ways to change the orientation of the incident linear polarization

Giono (2016, PhD) & Giono et al. (2016, SP)

プレゼンター


We performed … before the flight by developing a polarized Lya light source. According to this pre-flight polarization calibration as well as the in-flight one, we confirmed that the polarization error is smaller than 0.1% as we designed.

2016/09/15 CLASP in SPW8 10

CLASP was launched on Sep.3, 2015 in White Sands.

Ballistic flight:• max height: 261km.• ~300s in space (>150km).• returned safely.

プレゼンター


CLASP was launched on Sep.3rd last year from White Sands in US. It reached 260 km in height, stayed in space about 5 minutes, and then returned to the ground without any serious damages. It like a round trip between here and Rome.

[1] Initial ~ 16 sec Disk center for the on-flight polarization calibration.– SJ: >16 images with 0.6s cad.– SP: >33 images with 0.3s cad.

[2] ~ 30 sec for repointing.[3] Remaining ~ 289 sec

Sit & stare in QS near SW limb. Slit is perpendicular to the limb.– SJ: > 466 images with 0.6 cad.– SP: > 933 images with 0.3s cad.

Observing procedurePeak height was ~ 261 km.

[1]

[3]

[2]

2016/09/15 CLASP in SPW8 11

プレゼンター


Our target is the quiet Sun near the limb. So, we selected this south-west limb for the main observation, and put the 400 arcsec slit radially from 20 arcsec off-limb. However, in the initial 10 sec or so, we observed the disc center for the on-flight polarization calibration. The pointing was so stable as shown by this slitjaw movie. Drift was only 0.9” over the entire 4.5-min observation, and jitter was less than 0.15”.

[1] Initial ~ 16 sec Disk center for the on-flight polarization calibration.– SJ: >16 images with 0.6s cad.– SP: >33 images with 0.3s cad.

[2] ~ 30 sec for repointing.[3] Remaining ~ 289 sec

Sit & stare in QS near SW limb. Slit is perpendicular to the limb.– SJ: > 466 images with 0.6 cad.– SP: > 933 images with 0.3s cad.

CLASP Slitjaw(SJ) movie

Observing procedurePeak height was ~ 261 km.

[1]

[3]

[2]

Drift: < 0.9”

Jitter: < ±0.15” (PV)

2016/09/15 CLASP in SPW8 11

プレゼンター


We observed the quiet Sun near this south-west limb, by putting the 400 arcsec slit radially from 20 arcsec off-limb. However, initially we also observed the disc center for the in-flight polarization calibration. The pointing was so stable as shown by this slitjaw movie. Drift and jitter were much smaller than the pixel size.

2016/09/15 CLASP in SPW8 12

CLASP/SJ images with high pass filter

Many fast intensity fluctuations appear both in an active region and quiet Sun, after high-pass filter was applied.

“high-pass filter”1. Subtract a running average of 30s-int. from

the original images.2. Take a running average of 4.8s-int. to remove

the effect of the PMU rotation (4.8s/rot).

Kubo et al. (2016, ApJ)

プレゼンター


This page is not a topic for the polarization. But, high cadence Lya images taken by SJ are also interesting to investigate small transient events in the chromosphere.

Lyman-α Spectrum taken with Spectro-Polarimeter (SP)

O V 121.83 nmSi III 120.65 nm

Lα 121.57 nm

CLASP SJ imageCLASP SP images Ch1Ch2

2016/09/15 CLASP in SPW8 13

プレゼンター


In the SP camera, not only Lya but also OV and SiIII are seen. But here, I focus to the Lya line.

Wavelength: λ

Limb

Disk Center

μ =

arcsec

t-averaged λ-x plot

Lyman-α Polarization: Stokes-IQU• First detection of Lyα pol.:

1～6 % in the wing & ～0.5 % in the core.

• A clear C-to-L variation in the wing of Q/I, but NOT in the core.

• Positive Q/I above the limb.• Small-scale (10”～20”)

structures in Q/I and U/I as well as I:Not only local plasma

conditions (T, ne, etc.) but also local Bdistribution may affect the polarization signals.

Q/I U/IlogI

2016/09/15 CLASP in SPW8 14

6

–6

[% o

r 0.1

%]

0

6% 0.6% 6% 0.6%

プレゼンター


These are Stokes IQU for the Lya derived from the CLASP limb observation. Here, two polarization images in different scale are shown for each fractional Stokes signal. One is for +/-6% and the other for +/-0.6%. We actually detected the solar Lyman-alpha polarization for the first time, which is 1 to 6 % in the Lyman alpha wing and about 0.5 % in the core. Q/I signal in the wing shows a clear C-to-L variation: -1% in the DC side and -6% near the limb. In the line-core, no clear CLV is seen, but clearly positive Q/I appear in the core above the limb. We also found small scale structures along the slit both in Q/I and U/I signals, and both in the core and the wings.

Limb

Disk Center

μ =

Theoretical Prediction (Belluzzi, Trujillo Bueno, & Štěpán 2012)

Stokes Profiles

• The Q/I profile & CLV in Q/I wingare essentially consistent with the theoretical prediction.

But• The amplitude & peak separation

are slightly different with those in the FAL-C model. The CLASP observations can

help us constrain the structure of the quiet solar chromosphere.

U/I

Q/I

μ=0.3μ=0.5μ=0.7

Observed Pol. Spectra

-4

Q/IlogI

λ

-4

-4

0

0

0

2016/09/15 CLASP in SPW8 15

プレゼンター


Let’s move on more detail. These are the wavelength profiles at three different points (red, green and blue) as well as spatially averaged profile (black line). The Q/I signal is large in the wings and small in the core. The Q/I in the wings is large near the limb and becomes smaller toward the disk center. These properties are essentially consistent with the theoretical prediction by Belluzzi based on the FAL-C model. But, the amplitude and peak separation of the Q/I profiles are slightly different between the observation and the model. Therefore, these polarization data can help us constrain the structure of the solar chromosphere.

2016/09/15 CLASP in SPW8

Center-to-Limb variation

Observed Profiles along the slit

CLV in a 3D model (Štěpán et al. 2015) limb

limblimb center

wingcore• A clear CLV in the wing of Q/I,

following the (1-μ2) trend (dotted lines).• But not in the core of Q/I.

Chromospheric magnetic fields B (>100G) produce a very significant line-core depolarization by the Hanle effect.

16

プレゼンター


Here, CLV is more clearly shown as a function of the radial location. The black and red lines show the polarization in the wing and core averaged in these grey and orange areas. Q/I in the wing follows the (1-mu^2) trend shown by these dotted lines. However, we cannot see so clear trend in the core, even though Stepan expected the CLV even in the core based on a 3D model atmosphere. This no CLV in the core might indicate the existence of magnetic fields larger than 100G in the chromosphere. The actual sun is may be more complex than they expected in the model. And further investigations are required to understand the observed polarization.

• In a plane-parallel atmosphere without magnetic fields, the Lyα scattering polarization can be qualitatively understood:

– μ = cosθ : the angle between normal and LOS.

– 𝑱𝑱𝟎𝟎𝟐𝟐 : the anisotropy between vertical and horizontal illuminations of the atoms in the solar atmosphere.

• Q/I < 0 in the disk, because the pumping Ly-α radiation is predominantly horizontal.

• Q/I > 0 above the limb, because the vertical illumination dominates.

What was expectedin Scattering Polarization

Trujillo Bueno et al. (2001) limb centerθ

2016/09/15 CLASP in SPW8 17

• In the core (Štěpán et al. 2015),

• In the wing (Belluzzi et al. 2012)

プレゼンター


But here, I briefly consider the local structures in the polarization signals, using this formula in a plane-parallel atmosphere. This formula show two terms affect the polarization signals. One is mu, which corresponds to the angle between LOS and the normal of the atmosphere. The other is the anisotropy between vertical and horizontal illumination of the atoms.

Spatial Trends

• Global trend • Local trend– μ variation

– 𝑱𝑱𝟎𝟎𝟐𝟐 variation

2016/09/15 CLASP in SPW8 18

See talk by Štěpán, Trujillo Bueno et al.

プレゼンター


The global trend “CLV” is essentially understood by the change of the normal direction. In the similar way, the undulated atmosphere in a small scale affects the polarization signals through the mu variation. This effect may be related with the gradient of the intensity. The other term J20 must be affected by the local condition also. In this case, the effect may be related with the intensity.

Belluzzi & Trujillo Bueno (2016, in prep)

Lyα Int. vs. Linear Pol.• In a plane-parallel atmosphere (FAL),

they are anti-correlated.– FAL-P (plage model): Brighter ⇔ Smaller Pol. @ line wing– FAL-C (quiet Sun model): Fainter ⇔ Larger Pol. @ line wing

Belluzzi et al. (2012)

2016/09/15 CLASP in SPW8 19

プレゼンター


as indicated by these model calculations. It suggest the anti-correlation between Lya intensity and polarization.

How about in CLASP data:Lyα Int. vs. Linear Pol.

In the line wing,many of local variations in Pol. is anti-correlated with the intensity. Mainly, 𝑱𝑱𝟎𝟎𝟐𝟐 variation may

cause the local variation in Pol.

In the line core, a similar anti-correlation is seen in some areas, but largely scattered. Larger scatter than in the

wings might be affected by magnetic fields.

Int.

Pol.

Int.

Pol.

limb

limb

anti-correlation

anti-correlation

2016/09/15 CLASP in SPW8 20

プレゼンター


In the observed line-wing data, “many of local variations in linear polarization degree” indicated by colored segments “…”. Therefore, “mainly …” rather than only geometrical affect though mu-angle. In the case of the observed line-core data, “a similar …”.

Summary

• CLASP was successfully launched on Sep.3, 2015, and made a perfect Lyman-α spectro-polarimetric observation.

• A few % of polarization were observed in the Lyman-α wing, and a few of 0.1 % in the core.

• A clear C-to-L variation in the wing of Q/I, but NOT in the core.

• Small-scale (10”～20”) structures in Q/I and U/I as well as I.

2016/09/15 CLASP in SPW8 21

プレゼンター


This is a summary. We actually observed the scattering polarization in the Lyman alpha line. We found a clear CLV in the wing but NOT in the core. We also found small scale structures in the polarization signals.

Science Papers: in prep. & in press• High-precision UV spectropolarimetric observations

– Kano et al. : Discovery of scattering polarization in the Lyα line.– Ishikawa,R. et al. : Scattering polarization in Si III 120.6nm line and

indication of Hanle effect by comparing with Lyα.– Narukage et al. : Temporal variations of the polarization in the Lyα line.– Katsukawa et al. : On the possibility of scattering polarizations in the O-V line– Štěpán et al. – Trujillo Bueno et al.

• High-cadence Lyα imaging by Slitjaw optics.– Kubo et al. (2016, ApJ) : Fast-Propagating Intensity Disturbances– Ishikawa,S. et al. : Activities at Coronal-Loop Footpoints– Suematsu et al. : Spicules.

• Lyα spectral observation– Winebarger et al. : Spectral analysis of Lyα intensity profiles

• Polarization Calibrations– Giono et al. (2016, SP) : Pre-flight polarization calibration – Giono et al. : In-flight polarization calibration

2016/09/15 CLASP in SPW8 22

: Papers on interpretation by comparing with model calculations.

プレゼンター


Therefore, we expect these science papers will come out from the CLASP data. After this meeting, especially these papers on UV SP will be submitted step by step.

• The same optical design and structure, but for MgII h & k.

• And take Full Stokes.

• We will propose to fly in 2019 Spring!

What’s next?

Measurement of circular as well as linear polarizations

Observing target: QS and plage (if available)

Q/I (scattering pol. & Hanle) V/I (Zeeman)

Mg II h& k line core imageobtained by IRIS

Belluzzi & Trujillo Bueno(2012; ApJ letters).

CLASP2

2016/09/15 CLASP in SPW8 23

プレゼンター


We already submitted the re-flight proposal to NASA. It is CLASP2. Because the CLASP instrument returned to the White Sands desert without any significant damages, we will re-use the same optical design and the same structures. But, we will change to Mg II h & k and will take full stokes profiles of them.

• The same optical design and structure, but for MgII h & k.

• And take Full Stokes.

• We will propose to fly in 2019 Spring!

What’s next?

Measurement of circular as well as linear polarizations

Observing target: QS and plage (if available)

Q/I (scattering pol. & Hanle) V/I (Zeeman)

Mg II h& k line core imageobtained by IRIS

Belluzzi & Trujillo Bueno(2012; ApJ letters).

CLASP2

2016/09/15 CLASP in SPW8 23

プレゼンター


We are planning the re-flight, CLASP2, as reported by McKenzie’s poster, to observe another important UV lines, Mg II h & k.

Acknowledgement

The CLASP project is funded by:• US participation:

NASA Low Cost Access to Space (Award No. 12-SHP 12/2-0283). • Japanese participation:

JSPS KAKENHI Grant (No. 23340052, 24740134, 24340040, & 25220703), as well as JAXA’s and NAOJ’s internal research fundings.

• Spanish participation:Ministry of Economy and Competitiveness through project AYA2010-18029 (Solar Magnetism and Astrophysical Spectropolarimetry).

• French participation:Centre National d'Etudes Spatiales (CNES).

2016/09/15 CLASP in SPW8 24

プレゼンター


Finally, we acknowledge these fundings to support the CLASP project.

I’m R. Kano from NAOJ. I would like to show the CLASP ... · Lyman-αscattering polarization...

Documents

Transcript of I’m R. Kano from NAOJ. I would like to show the CLASP ... · Lyman-αscattering polarization...