Differences between central and peripheral umbral dots

Michal Sobotka1

Jan Jurcak2,1

SXT seminar, 2008/10/10, NAOJ

Astronomical Institute, Academy of Sciences of the Czech Republic

National Astronomical Observatory of Japan

Observations

Sunspot NOAA 10944 observed with Hinode SOT on February 27, 2007 between 12:00 UT and 15:00 UT. Heliocentric angle around 13 deg.

G-band images taken with cadence of 1min. 8” x 16”

Observations

Sunspot NOAA 10944 observed with Hinode SOT on February 27, 2007 between 12:00 UT and 15:00 UT. Heliocentric angle around 13 deg.

Repetitive scanning of 10” wide area with SP (normal mode).

SIR inversion

34 consecutive SP scans of area with the size of 50 x 100 pixels was inverted.

The standard version of the SIR code was used.

One-component model of atmosphere considered.

No stray-light taken into account (so far).

We allowed for the changes of plasma parameters with height. Five nodes was used for the temperature, magnetic field strength and inclination, and LOS velocity.

The results were studied at two different layers:

low atmosphere: averaged between log(tau)= -0.2 and -0.5

high atmosphere: averaged between log(tau)= -1.4 and -2.0

Maps of plasma parameters

LOWATMOSPHERE

HIGHATMOSPHERE

Penumbral grain

Event – low atmosphere

Surroundings – low atmosphere

Event – high atmosphere

Surroundings – high atmosphere

Penumbral grain – peripheral umbral dot

Event – low atmosphere

Surroundings – low atmosphere

Event – high atmosphere

Surroundings – high atmosphere

Peripheral umbral dot

Event – low atmosphere

Surroundings – low atmosphere

Event – high atmosphere

Surroundings – high atmosphere

Central umbral dot

Event – low atmosphere

Surroundings – low atmosphere

Event – high atmosphere

Surroundings – high atmosphere

Conclusions

Conclusions

In the low photosphere, CUDs have a weaker B and their LOS velocity and inclination do not differ from the surroundings.

In PGs, B is reduced with respect to the surroundings. PGs show strong upflows of 1 km/s and the magnetic field is more horizontal. PGs move into the umbra with horizontal velocities of about 400 m/s.

PUDs have a substantially higher T and a weaker B than in the surrounding umbra. They conserve the characteristic vertical upflows of PGs and higher field inclination compared to the surroundings. These parameters decreasegradually during the motion of PUDs into the umbra. The speed of horizontal motion of PUDs is practically equal to that of PGs.

In the high photosphere, the differences between the bright features and their surroundings are not so significant. The temperature excess in PUDs indicates that PUDs can penetrate higher in the photosphere than CUDs.

Evidence of convective rolls in a sunspot penumbra

V. Zakharov, J. Hirzberger, T. L. Riethmüller, S. K. Solanki, and P. Kobel

Max-Planck-Institut für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany

ObservationsNOAA 10904

2006/08/13

Θ= 40.5 deg

2 hour long sequence

SP data obtained withSolar Optical Universal Polarimeter

6 wavelengths in 123 s[-150, -75, 0, 75,150, 250]

ME inversion appliedHeLIx code

Orientation of the filament: 21 deg with the respect to the nearest limb (sin 21=0.36)

Results

Limb side of the filament shows: Center side of the filament: Velocity Blueshift Weak redshiftField strength Weker filed Strong fieldInclination Almost horizontal More verticalAzimuth Points toward the limb (20 deg) Parallel to the filament

Results

Conclusions