1 Sunspot Studies in Oslo with CDS,SUMER,MDI and TRACE A final report (maybe). Per Maltby NilsBrynildsen Olav Kjeldseth-Moe, Per Maltby, Terje Fredvik and Nils Brynildsen Institute of Theoretical Astrophysics University of Oslo

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

3 Oslo Sunspot Studies O_SPOT1 – raster of (4) wide slit images at three wavelengths O_SPOT2 – limited spatial extent, but many lines, reasonably high cadence raster reasonably high cadence raster O_SPOT3 - coarse raster to replace O_SPOT1 O_SPOT4 - a “sit and stare” study for rapid time variations O_SPOT5 - large FOV, reasonable cadence, raster (incomplete area coverage, stripes) (incomplete area coverage, stripes) O_SPOT10 – GIS study for sunspot oscillations. O_SPOT11 – NIS study for sunspot oscillations.

4 Oslo Sunspot Studies (2) Study Spectro- Slit Step Number of FOV of Exp. Cadence Name meter # size Locations/ one rst. time (duration) (as) Rasters (as^2) (s) (m:s) ========================================================== O_SPOT1 NIS /4 240x :04 O_SPOT2 NIS /1 120x :36 O_SPOT3 NIS /1 236x :20 O_SPOT4 NIS 3 drift 150/1 8x80(?) 5 20:30 O_SPOT5 NIS /1 238x : O_SPOT10 GIS 2 drift 145/6 11x :50 O_SPOT11 NIS 4 drift 250/1 13x :00 ========================================================== Studies marked drift have step size 0 a.s. and no rotational compensation Number of locations marks number of exposures defined as a single raster Solar drift rate x raster duration defines extent of raster in x-direction

5 Wavelength list Ion l (Å) T(K) #1 #2 #3 #4 #5 #10 #11 ===================================== He I x He I x x x x F x O III x x x u O VI x x x x l x O V x x x x x l x Ne VI x x x x Mg VIII 315 xxx xxx x G Mg IX x x x x x I x Fe XIV x S Fe XVI x x x x

6 Number of spots/runs YearNumber of SunspotsNumber of days

7 Data reduction of O_SPOT data All CDS data are corrected using standard CDS software, transformed to absolute intensity, and processed as follows: -- Intensity and velocity maps from line profiles fitted to Gaussians. Blends removed before fitting. -- Routines for conditional probability analysis used on selected emission lines. -- Power spectra and relative integrated line intensities calculated for spectral lines to study the 3 minute oscillations. -- CDS data are often co-aligned and compared with data from SUMER, MDI or TRACE.

8 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.

9 Rapid time variation in the emission - topic 3 Temporal variation in the emission from active regions are rapid. –Obvious changes in the emission are clearly distinguished over a 5 min time interval. –Variations over at 2 min interval may be seen. –Study O_SPOT1: Raster with the CDS wide slit. –I shall recommend the use og this mode if it is now again to be allowed!

10 - 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.

11 Sunspot Plumes - topic 1 Rediscovery of sunspot plumes –Originally described by Peter Foukal (1976) based on Skylab data. –Plumes were rediscoverd by Maltby and Brynildsen. –A slight, but fruitful change was made in the definition of plumes. Observing programmes: O_SPOT2 and O_SPOT 5. –Designed for mapping of sunspot plumes and studies of flows in and around spots.

12 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.

13 - Mapping of plumes - Located above the white light spot - I > 5 x  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)

14 - Mapping of plumes - Located above the white light spot - I > 5 x  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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16 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 N V and O V lines. Sound speeds plotted in

17 Regions with dual flows Sunspots with dual flows in O V and N V in 4 active regions. Area fractions with supersonic dual flow components range from ~1% to 38% for O V in the umbra of AR8998.

18 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

19 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.

20 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??

21 NIS Oscillations

22 GIS/NIS Oscillations

23 Amplitudes, their temperature dependence and frequencies 1.Distribution of intensity amplitude values. –Intensity amplitudes in the range Amplitudes as a function of temperature. –Maximum amplitudes at ≈100,000 K 3.Frequency of oscillations - distribution. –Frequencies mHz -- 3 min min periods

24 Intensity and velocity variations

25 Arguments for sound waves Intensity and velocity variations are in opposite phase (previous slide). Comparison of observed velocities and velocities calculated from intensity variations.

26 Sound wave equation for a polytropic gas  = f(v). I = constant x   -->  c I 1/2. A perfect fit if we allow for the helio- centric position of the sunspot! Cont.: Observed and Calculated velocity

27 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.

28 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 10 5 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

29 Oscillations in the corona. 171 Å TRACE band: – ~50 s cadence. – Left: image - Right: difference image. On top of white light contour of sunspot from MDI. Oscillations seen in a limited area inside the umbra: – At footpoints of loops ectending to the corona. Are there similar penetration of waves to the corona outside of sunspot umbrae?

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