JOP161 SOHO Comprehensive Footpoint Study Proposal for SUMER Mini-Campaign Spring 2003 (March/April) AUTHORS : Scott W. McIntosh, Art Poland VERSION : Draft (10 September 2002) Targeted time changed by SOC (12 September 2002) Updated (10+21 March 2003) Differences INSTRUMENTS : SOHO[SUMER, CDS, EIT, MDI], TRACE SCIENTIFIC OBJECTIVE : We intend to study, at the highest possible temporal and spatial resolution, the velocity, intensity and hence the Differential Emission Measure (DEM) structure of an off-active region loop footpoint. The goal of obtaining this dataset is to have input for and study the applicability of static and non-static loop models to the problem of understanding the dynamic nature and physical structure of magnetic flux elements. SCIENTIFIC JUSTIFICATION : A previous run of SOHO/TRACE JOP72 (SUMER/TRACE/MDI, May 17 1998; 1500-1700 UT) has provided a valuable dataset to study chromospheric dynamics. Almost as a side-project the structure/dynamics of the transition region at temperatures between 100,000K and 700,000K could be studied through the UV emission lines around the Ne VIII pair at 770, 780 Angstrom. Unfortunately, this side project had no high-temporal cadence TRACE counterpart, ie TRACE was observing continua, and not 171 (or 195). Through the analysis of the [770,780] SUMER data we have noticed that there are features in the derived footpoint Doppler velocities that would eliminate certain classes of theoretical models from their temporal variation alone. Justification for the inclusion of CDS data is to bridge a gap in temperature space between O V and Ne VIII using some of the cooler, but bright, lines observed by CDS [e.g., OIV 554.28; OV 629.74; NeVI 562.80; HeI 584.33; MgIX 368.06; He II 303.78 (in second order)]. We would like to have the four-filter image EIT data to study the Local DEM context of the AR and to provide context for the computations that will be made with the SUMER and CDS datasets. MDI and TRACE will allow for field extrapolation and study of the high-resolution coronal context for the hour long sequences. OPERATIONAL CONSIDERATIONS : Target selection will be made one or two days in advance. A target near disk center would be best to eliminate projection effects as much as possible. We will project which active region to target and extrapolate the SUMER and CDS pointing from that automatically. Of course, we will be able to monitor the pointing to see if our extrapolation will yield the desired results. Observations will last for only one hour, but should be scheduled as a Target Of Opportunity JOP over the whole MEDOC Campaign #10 time span to ensure a good target can be found. [With a high-cadence EIT sequence, scheduling may have to be restricted to a time period when NRT is available. High-cadence EIT not required this time.] OBSERVING SEQUENCES : SUMER - (1x120 slit, detector B) Hour long sequence in the 760-790 wavelength range with 12.5 second exposures to get good profiles and signal-to-noise. Will also allow for accurate removal of blends in the 50 pixels spectral windows; these blended lines can be used in the analysis. Spectral windows in this study: OV (760.228); NIV (765.143); NeVIII (770.324); NeVIII (780.324); OIV(787.71) CDS [NIS] - (QUICK/v6: 26x150 raster with 2x240 slit) Complimentary lines to SUMER, those spanning the same temperature range and filling the temperature gap between OV and NeVIII. Need CDS to raster estimated SUMER position (+/-13 arcseconds) whence post-analysis will ensure cross-correlation between the individual observations at each timestep. Spectral lines : OIII (559.56); OV (629.74); NeVI (562.80); HeI (584.33); MgIX (368.06); He II (303.78; in second order) MDI - If the AR is in the high-resolution field of view then it would great to have high-res B and V. EIT - Selected AR, four-filter imaging to extract spatial derived DEM for context. As high a temporal cadence as is safe for the instrument. Function will be performed with standard synoptics before CDS/SUMER/TRACE sequences. TRACE - High-Cadence 171/195 imaging. Alternate images to ensure that correlation between SUMER/CDS and TRACE over the footpoint is accurate and to add to the analysis. 1600 angstrom continuum image taken to provide chromospheric pointing context.