2005/11/08 6th Solar-B Science Meeting@Kyoto 1

Supersonic downflows in the photosphere discovered in sunspot moat regions

T. Shimizu (ISAS/JAXA, Japan),

V. Martinez-Pillet, M. Collados,

B. Ruiz-Cobo, R. Centeno (IAC, Spain),

C. Beck (KIS, Germany),

Y. Katsukawa (NAOJ, Japan)

Report a discovery from international time program observation at Canaries islands on July 2005

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Remarkable Stokes V profiles we have found!

Extremely red-shifted signal Frequently observed in sunspot moat regions.

Photospheric Si I 10827A by TIP

400mA => 11km/s!! Slit direction wavelength

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Observations

Tenerife Infrared Polarimter (TIP; Martinez Pillet et al. 1999)– Attached to German VTT, Tenerife– Four Stokes profiles of photospheric Si I lin

e at 10827A (g=1.5)

Polarimetric Littrow Spectrograph (POLIS; Beck et al. 2005)– Simultaneous mapping of four Stokes of F

e I 6301.5A(g=1.67)/6302.5A (g=2.5)– Note: same spectral lines measured with S

olar-B Spectro-Polarimter

Leading spot of AR 10781 on 3 July 2005

He I 10830Si I 10827

TIP Stokes I

VTT

POLIS Stokes I

Fe I 6301.5 Fe I 6302.5

2005/11/08 6th Solar-B Science Meeting@Kyoto 4

Morphological properties of downflows (1)

Red-shifted signal has opposite-polarity near the edge of sunspot (positive)-polarity flux patches– 11 of 25 near the edge of positive-flux patch – 19 of 25 opposite-polarity red-shifted signal

40“x45“ FOV Location of extremely red-shifted events

“25 events” were found in three scan maps of a sunspot moat region.

Q

U

V

I

3.4”

([enhanced] magnetogram generated from Stokes V data)

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Morphological properties of downflows (2) Size extremely small-scale phenomena

– Scan direction: 0.9 – 1.2 arcsec (3 – 4 scan positions, 0.3” step)– Slit direction: 0.7 – 1.0 arcsec (4-6 pixels, 0.17”/pix)

Observed not only in Si line but also in Fe 630nm lines– Si I 10827A + Fe I 6301.5 + FeI 6302.5 16 event (64%)

– Si I 10827A + Fe I 6301.5 only 2 event ( 8%)

– Si I 10827A only 7 event (28%)

Duration <1hr, but exactly unknown because of slit scanning observation

I

Q

U

V

TIP: Si 10827A POLIS: Fe I 6301.5/6302.5A

3.4”

500mA 300mA

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Estimate physical conditions

SIR inversion was applied to 7 events (Dr. Ruiz-Cobo)– 3 lines are simultaneously fitted – Assumed to have two magnetic components with constant parameters

(magnetic field, velocity), and 2 different temperatures, one for each magnetic component.

Preliminary comfortable results have been derived for only limited number of events.

Event 1-0 pos 6

2005/11/08 6th Solar-B Science Meeting@Kyoto 7

Estimate physical conditions

The downflowing component has a higher field strength than the rest component, and it has relative downflows as large as 10 km/s. Also, the downflowing component seems to be hot by some 100 K or so.

Event 1-0 pos 6 Restmagnetic

component

Downflowing magnetic

component

B (gauss)

v (km/s)

Inclination (deg)

1072 1533

12.2 2.6

156 180

Temperature (K) solid dotted

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Discussions downflows as large as 10 km/s

– Compared with sound speed ~5 km/s (T~5500K)

Alfven speed ~16 km/s (B~1500g, n~ 7x10^-8 g/cm3)

– The observed downflows are supersonic but slightly below Alfven speed.

We currently think that the observed supersonic downflows may be a signature of downwarding outflow from magnetic reconnections occurring at the chromosphere or upper photosphere.

No “transient” brightenings were observed in TRACE 171A coronal images.

Dutch Open TelescopeCa II H movie for map 1

(9:05-9:35UT, same FOV)

2005/11/08 6th Solar-B Science Meeting@Kyoto 9

Summary We found events with extremely red-shifted Stokes V signal

in sunspot moat regions. They have following properties:

– Measured with photospheric Si I 10827A line but also with Fe I 630nm lines.

– In order of one arcsec or smaller size.

– As large as 10 km/s, which is supersonic but still below Alfven speed.

– The downflowing component has a higher field strength than the rest component, and seems to be hot by some 100 K or so.

The observed supersonic downflows may be a signature of downwarding outflow from magnetic reconnections occurring at the chromosphere or upper photosphere.

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Further investigations with Solar-B

Full Stokes of Fe I 630nm lines will be measured in higher spatial resolution (0.16arcsec) with SOT/FPP Spectro-Polarimter.

Further understanding of this new phenomenon can be provided with Solar-B coordinated observations among SOT spectro-polarimter, filter imagers, and EIS.

Complicated Stokes profiles will be expected much more frequently. Some may be caused by flux tube dynamics, predicted by simulation (Steiner et al.).

Inversions of Stokes profiles will play key roles in interpreting such Stokes profiles.