Ryohko Ishikawa (NAOJ/Univ. Tokyo)
Saku Tsuneta (NAOJ)
Andreas Lagg (MPS)

New insights from
Hinode-VTT He10830
observation

Hidden magnetism
as revealed withHanle effect(Trujillo Bueno etal. Nature 2004)?

Cutoff due to thethreshold and/or thesensitivity issue ofZeeman effectPurpose: Finding chromosphericGreen: Vertical field, 13G
counterparts of THMFs (transient
Yellow: THMF, 140G
horizontal fields) seen in the photosphere(2008/04/29-2008/05/12)

Hinode-VTT joint campaign (HOP71)

PlageAvrett et al. 1994

Cell center

Averaged QSBright network

Number density of 2s3 S levelof He I vs Height1083nm: 2s3S-2p3p0 absorption+A few G to kG magnetic field canbe detected with Hanle and Zeeman
effect+Inversion of Stokes profiles isavailable (understood)+Simultaneous observation withphotosphere of Si (easy to performalignment with Hinode/SOT)VTT-TIP He 1083 nm

B2≈P
Chromosphere: ~10^{6} m = 1000 km = 10 Hp
8π
Pch ~ e^{-10}Pph  Bch ~ e^{-5}Bph = 2.7 GB ≈ 8πP The magnetic field would be detected only by Hanle effect.

Pph; Gas pressure @ photosphere
Bph; field strength of THMFs @ photosphere, average: 400 G

THMFs reach the chromosphere?

SP FOV:15”x82”, TIP FOV: 20”x78”
Cadence: 7.5min

SOT-NFI Na D magnetogram

Observation

Linear pol.

sqrt(Q^2+U^2)

Continuum

Stokes-I

Stokes-V

Circular pol.

Hinode/SOT-SP FeI 630 nm

FOV:15”x82”

Stokes signals aredominated by Zeeman
effect.

Photosphericmagnetic
signals

Linear pol.

sqrt(Q^2+U^2)

Intensity

Stokes-I

Stokes-V

Circular pol.

VTT-TIP HeI 1083 nm

FOV:20”x78”

Integration time: 7sec
S/N: 7x10^{-4}
Spatial resolution:0.64”(scan direction), 0.72”(slit direction)

Stokes signals are
dominated by Zeeman
and Hanle.

Completely different
from photosphere!!!

ChromosphericmagneticsignalsLinear pol.

sqrt(Q^2+U^2)

Intensity

Stokes-I

Stokes-V

Circular pol.

VTT-TIP HeI 1083 nm

FOV:20”x78”

Stokes-V

Integration time: 7sec
S/N: 7x10^{-4}
Spatial resolution:0.64”(scan direction), 0.72”(slit direction)

Stokes-U

Stokes signals are
dominated by Zeeman
and Hanle.Hanle!

Stokes-Q

Completely different
from photosphere!!!

Example of Stokes profile
Chromosphericmagnetic
HeSi
Stokes-I
signals

Linear pol.

sqrt(Q^2+U^2)

Intensity

Stokes-I

Stokes-V

Circular pol.

VTT-TIP HeI 1083 nm

FOV:20”x78”

Change of magnetic field
vector in Hanle regime(field strength, azimuth,inclination)

Change of LP

Stokes signals havechanged in 7.5 min!!!

Chromosphericmag. signals
7.5 min laterPhotosphere(FeI 630nm)

Linear Pol.

Circular Pol.

LP between negative and positive
patches in the photosphere

Stokes-I

Chromosphere(HeI 1083nm)

8”

Possible case of emerging fluxin the chromosphereseparating

Photosphere(FeI 630nm)

Circular Pol.

Stokes-I
Linear Pol.

7.5min later

Chromosphere(HeI 1083nm)

8”

Possible case of emerging fluxin the chromosphereStokes-I

Chromosphere(HeI 1083nm)

Photosphere(FeI 630nm)

Linear Pol.

8”

Circular Pol.

Disappearance of chromospheric fields withphotospheric magnetic cancellation

Photosphere(FeI 630nm)

Circular Pol.

Stokes-I
Linear Pol.

7.5min later

Chromosphere(HeI 1083nm)

8”Disappearance of chromospheric fields withphotospheric magnetic cancellation

Stokes-I

Chromosphere(HeI 1083nm)

Photosphere(FeI 630nm)Linear Pol.

4”

Circular Pol.

Sudden appearances of chromosphericmagnetic fields without photospheric signature

Photosphere(FeI 630nm)

Linear Pol.

Circular Pol.

7.5min later

Significant difference in photosphericmagnetic fields are not seen.

Stokes-I

Chromosphere(HeI 1083nm)

4”

Sudden appearances of chromosphericmagnetic fields without photospheric signature••Seeing free He 1083 observation potentially brings us to the newworld of chromospheric magnetic fields.

– He 1083 nm needs coronal illumination, and it may be difficult to observe thepure quiet region. Further verification should be needed.
– Spatial resolution (0.5”@50cm telescope) is not as good as that in visible
light.

*Disadvantage*– Long integration can be done, and we will be able to detect much weakermagnetic signals.
– Spectro-polarimetry is compatible with high spatial resolution.

*Lessons learned from Hinode observation*– Purely chromospheric– Enable us to detect 1G to a few kG with Hanle & Zeeman effects– Easy to interpret (inversion code is already available)*Nice feature of He 1083*– Chromospheric small loops with the size of a few granules are detected.
– Magnetic signal s without photospheric counterparts are also found.

Chromospheric magnetic fields appear to be completely different fromphotosphere: for example.

New insights from He 1083nm

Quantum efficiency of detector
Solar-C:60% (NICMOS)
VTT:60% (NICMOS)

Telescope and spectrograph throughput
Solar-C:13.4% (assume SOT-SP at 630.2nm)
VTT:1% (assume 70% atmosphere transmission)

Size of telescope
Solar-C:50cm
VTT:70cm

S/N comparison between
VTT and Solar-C

Factor of 1 gain

Factor of 13.4 gain

Factor of (5/7)^2 gain

Integration time: 24sec
S/N: 4x10^{-4}
Pixel size: 0.5”

VTT-TIP He 1083nm

Factor of (5/7)^2 gain

Integration time: 24sec
S/N: 4x10^{-4}
Pixel size: 0.5”

Quantum efficiency of detector
Solar-C:60% (NICMOS)
VTT:60% (NICMOS)

Factor of 1 gain

Solar-C exposure
Solar-C relative
time :
Telescope and spectrograph throughput
to VTT:
Solar-C:13.4% (assume SOT-SP at 630.2nm) 24 sec/7
Factorof 8 gain
<4sec
VTT:1%(assume 70%Factor
ofatmosphere
7 gain transmission)

Size of telescope
Solar-C:50cm
Total
gain of
VTT:70cm

S/N comparison between
VTT and Solar-C

VTT-TIP He 1083nm

Factor of (5/7)^2 gain

Integration time: 24sec
S/N: 4x10^{-4}
Pixel size: 0.5”

+Achieve better S/N by increasing integration time
+Scan with higher cadence keeping the good S/N+Achieve better spatial resolution keeping good S/Nof 7 more sensitive than VTTQuantum efficiency of detector
Solar-C:60% (NICMOS)
Factor of 1 gain
VTT:60%50cm(NICMOS)
Solar-C telescope is factor

Solar-C exposure
Solar-C relative
time :
Telescope and spectrograph throughput
to VTT:
Solar-C:13.4% (assume SOT-SP at 630.2nm) 24 sec/7
Factorof 8 gain<4sec
VTT:1%(assume 70%
Factorofatmosphere
7 gain transmission)

Size of telescope
Solar-C:50cm
Total
gain of
VTT:70cm

S/N comparison between
VTT and Solar-C

VTT-TIP He 1083nm