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



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.


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.


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.]


          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.