Updated: 3 June 1999 SOHO Joint Operations Program 108 DYNAMICS AND STRUCTURE OF LARGE SUNSPOTS Authors: R. A. Shine, Peter Brandt, Julia Saba, Ted Tarbell SOHO Instruments and contacts: TRACE: R. Shine, C.J. Wolfson, T. Tarbell, K. Schrijver MDI: J. Saba GBO Instruments and contacts: SVST at La Palma: Peter Brandt, Michal Sobotka Objective: To obtain a comprehensive set of high resolution images in a large sunspot to study small scale photospheric structures and their effect on, or interaction with, chromospheric oscillations and coronal loops originating from the sunspot. Also of interest are the moving magnetic features (MMF's) in the moat area surrounding large sunspots and any possible interaction or relationship with higher coronal structures. Observations that span the initial assembly of a large sunspot and/or it's decay would be especially useful. Observations: The primary data sets for this campaign are observations from the Swedish Vacuum Solar Telescope (SVST) on La Palma, the TRACE satellite, and the MDI instrument on SOHO. However, it would greatly benefit from coordinated observations with CDS and SUMER. The CDS program o_spot2 (see JOP 18) and SUMER spectra across the sunspot are possible examples. Any other groundbased observations of the same sunspot would also be very valuable, especially Stokes field maps (e.g., the ASP instrument at Sac Peak), additional H alpha and K line movies, K line spectra, and photospheric dopplergrams. SVST La Palma ------------- The configuration at La Palma will include: WL camera: 5000A narrow band continuum filter, 2Kx2k CCD G band camera: 10A wide filter centered at 4305A, 2Kx2K CCD K line camera: 3A wide filter centered qt 3934A, 2Kx2K CCD Tunable filter, H alpha, 5576, 6302, 1.6Kx1K CCD This assumes that the 2Kx2K CCD systems are operational, otherwise smaller CCD's will be used. The G, K line, and continuum cameras will store a frame selected image about every 20s. We may only be able to do two of the first three bands above (WL, G, and K). In this case the G band may be dropped since the 5000A band shows umbral dots and penumbral grains better. The tunable filter can be used in several lines but we expect to primarily use it for several positions in the H alpha line to produce chromospheric Dopplergrams. Photospheric Dopplergrams (taken in the magnetically insensitive 5576A Fe I line) to study the Evershed effect may also be made at times with the tunable filter. Because of the tradeoff between the cadence and the number of wavelength positions, several different programs emphasizing one or the other will be run. If MDI magnetograms are not available, the 6302 line can be used to obtain RCP/LCP images for longitudinal magnetograms. The phenomena visible with the SVST data include umbral dots, penumbral grains, umbral flashes and oscillations, running penumbral waves, and MMF's (seen in G and K) in the moat area surrounding the sunspot. TRACE ----- In order to investigate a range of time scales as well as the relationships between phenomena at different levels in the atmosphere, several TRACE programs with different tradeoffs are required. Some of these will be particularly suitable for CDS or SUMER participation. A good configuration for the bulk of the observations would be Fe IX/X 171, 1600, and white light (wl) with a cadence of about 40s. To investigate short period oscillations, some observations using only a single EUV wavelength are needed for all 3 EUV lines (Fe IX/X 171, Fe XII 195, and Fe XV 284) for at least an hour each. Similarly some 1600 only observations are desired for about an hour at a time. Other combinations including more channels are desirable to establish the temperature structure. These can be done in a "context" mode that interrupts a higher cadence program every hour for several minutes. Expected phenomena in the TRACE data (based on previous observations) are oscillations in coronal loops overlying the penumbra, possible oscillations in the rare loops that connect to the umbra, and apparent outflows from loops associated with sunspts. We will be looking for coronal responses to K line umbral flashes, motions of penumbra grains, and the running penumbral waves seen in H alpha. MDI --- MDI magnetograms, preferably in the high resolution mode, are needed for the sunspot penumbral and moat structures. Dopplergrams and continuum filtergrams are both strongly desired, using a smaller field of view if necessary to uplink all 3 of these observables. If a choice is necessary, we would give the continuum images the lowest priority. Most sunspots will not cooperate by being in the high resolution fov, in which case full disk magnetograms, Dopplergrams, and continuum filtergrams, with the fov cropped to downlink all three, are desired. SUMER ----- SUMER observations similiar to the JOP 18 program would be appropiate for this investigation. A basic program would be a raster of the area including the sunspot once a day followed by high cadence spectra in O V (629), N V (1239, 1243), and Si II (1260) for at least one hour with the slit crossing the center of the sunspot. The cadence needs to be high enough to resolve oscillations down to 120s in the sunspot. The best time to run the program will be between 8-12 UT to increase the odds of good simultaneous La Palma results. Longer runs would also be useful of course. Post alignment of the results will let us compare the H alpha oscillations with the higher temperature SUMER lines. CDS --- CDS observations similiar to the programs described in JOP's 18 and 92 would be appropiate for these sunspot studies together with some higher cadence programs if feasible. The detailed daily plan will depend on the target, whether it might flare, etc. The O_SPOT program is a good general candidate but some runs of higher cadence programs like the single position LOOPS_3 (positioned to cross through the umbra and penumbra) would be desired for an hour or so during the prime La Palma time (8-12UT). EIT --- EIT full disk observations will provide context. If possible, some higher cadence rasters over a limited area including the sunspot would be desirable in the He II 301 channel. targets ------- The target could be any large sunspot available during the scheduled time of the SVST observations provided it is within about 50 degrees of sun center. Ideally a large sunspot will be tracked from about east to west across sun center and through the MDI high resolution feild of view. If we are blessed with more than one potential target, we would probably choose the region with the highest flare potential and combine this program with a flare watch. Target selection will be decided a day in advance of each daily observation to accomdate TRACE scheduling requirements. A daily telephone communication between La Palma and the SOHO teams will decide specifics. Schedule -------- The SVST is scheduled from June 6-22, 1999 for this program. Observations will be made at the SVST from about 7:30 UT to 18:00 UT with prime observing in the 8:00 - 12:00 UT period. TRACE and MDI coordination for the 10 hour period from 8:00 - 18:00 UT is requested. Additional coverage of the selected active region outside this time period is desirable to follow longer term trends. If we are not lucky enough to have a good target, the SVST and TRACE/MDI teams may choose to pursue another cooperative venture or run independently.