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Sunspot Studies in Oslowith CDS,SUMER,MDI and

TRACE A final report (maybe).

Olav Kjeldseth-Moe, Per MaltbyPer Maltby, Terje Fredvik and NilsNils

BrynildsenBrynildsen Institute of Theoretical

AstrophysicsUniversity of Oslo

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Program History

• Sunspot studies with SOHO instruments from 06/1996.

• Study the transition region and corona above spots, particularly the fast down flows into sunspot umbrae observed with HRTS.

• Redshifts in the transition region in general. • Sunspot plumes and 3 min oscillations in the

sunspot umbrae chromosphere and transition region.

• O_SPOT – studies run between 26 June 1996 and 22 February 2005.

• A total of 133 sunspots observed on 209 days.• All O_SPOT data are processed into intensity and

velocity maps.

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Number of spots/runs

YearNumber of Sunspots

Number of days

1996 4 6

1997 8 24

1998 10 18

1999 20 30

2000 28 41

2001 23 36

2002 17 30

2003 12 12

2004 7 8

2005 4 4

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Topics for investigations.

1. Rediscovery of sunspot plumes:• Definition and characteristic properties.• Downflows in plumes • Upflows?

2. 3 min oscillations in the sunspot transition region umbra:

– Oscillation studies of sunspots with NIS and GIS for proper temperature mapping in the TR.

– Nature of the oscillations.– Extension of oscillations into the corona.

3. Rapid time variability of sunspot emission. 4. Multiple line profiles and dual flows in

sunspots.5. Relations between intensities, flows and

magnetic fields inside active areas.

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- A 50 arc sec overlapping area, with ~30 s and ~2 min cadence

- Easy to distinguish changes over 5 min time periods. - Perceptible changes over time spans of ~2 min.

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Intensity and flows in plumes

• Concentrations of EUV line emission in bright "plumes" over sunspot umbrae.

• Strong emission and high red-shifts, i.e. down flows, in plumes. – Downflow velocity increase with temperature

to a max at log T ~ 5.5.

• Flow field in the low corona differ markedly from that in the transition region.

• Upflows missing in the 120” x 120” FOV.– Upflows somwhere in an extended region? - to

be checked.

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- Mapping of plumes- Located above the white light spot- I > 5 x <I> i.e. yellow contour- Max visibility at 0.25 MK – do not occur in corona, i.e. cool- Down flows into the spots in TR- No corresponding up-flows- No systematic flows in corona- Up-flows in extended area? (large raster)

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- Mapping of plumes- Located above the white light spot- I > 5 x <I> i.e. yellow contour- Max visibility at 0.25 MK – do not occur in corona, i.e. cool- Down flows into the spots in TR- No corresponding up-flows- No systematic flows in corona- Up-flows in extended area? (large raster)

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Supersonic dual flows - topic 4

Left (top): Gaussian line profiles and zero shift.Left (bottom): Dual flow line profiles, v ~100 km s-1.Right: Line of sight velocities for dual NV and OV lines. Sound speeds plotted in

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Regions with dual flows

Sunspots with dual flows in OV and NV in 4 active regions.Area fractions with supersonic dual flow componentsrange from ~1% to 38% for OV in the umbra of AR8998.

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Intensities, line shifts and magnetic fields - topic 5

• Line profiles with large intensities and red shifts above the average constitute an increasing fraction of the profiles as the relative wavelength shift increases

• Line profiles with large intensities and blue shifts compared to the average, on the other hand, constitute a decreasing fraction of the profiles as the relative wavelength shift increases

• Results have been obtained by conditional probability analysis

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Conditional probabilities for redshifted (blueshifted) with larger than average

intensity as a function of the velocity.

Left: Sumer results for 6 different lines.Above: Comparison of SUMER and CDS data. Full line: redshifts; dotted line: blueshifts.

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Oscillations and GIS studies- topic 2

• OSPOT_11 and OSPOT_10 for studies of oscilliation with NIS and GIS, respectively.– SUMER studies of oscillations

• Confirm presence of 3 min oscillations in sunspot umbrae found at 100,000 K (CIV 155 nm lines) by Joe Gurman.

• Are sunspot oscillations sound waves?• Temperature mapping of oscillations.

– Do they extend to the corona?? Do they extend to the corona??

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NIS Oscillations

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GIS/NIS Oscillations

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Amplitudes, their temperature dependence and frequencies

1. Distribution of intensity amplitude values.– Intensity amplitudes in the range 0.05-0.15.

2. Amplitudes as a function of temperature.– Maximum amplitudes at ≈100,000 K

3. Frequency of oscillations - distribution.– Frequencies 5.5 - 6.5 mHz -- 3 min - 2.5 min periods

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Intensity and velocity variations

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• Sound wave equation for a polytropic gas = f(v).

• I = constant x --> c I1/2.

A perfectfit if weallow forthe helio-centric positionof the sunspot!

Cont.: Observed and Calculated velocity

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Blue wing - red wing variations.• Oscillation amplitudes larger in the blue line wing than in the red wing.

• Compression is larget when the gas is moving in the direction that the wave propagates, i.e. towards us for an upward running wave.

• Max power at the same period in both wings.

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Oscillations summary so far

• Oscillations with periods ~ 3 min are seen both in intensity and in line-of-sight velocity above sunspot umbrae

• Maximum intensity is nearly in phase with maximum velocity directed towards the observer.

• Oscillation amplitude above the umbra increases with increasing temperature to a maximum for lines formed ~ 2 x 105 K, and decreases for higher temperatures.

• Oscillations are more pronounced in the blue than in the red wing of the lines

• Supports running progressive waves

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