SOHO Joint Observing Plan 012: Limb Prominences

CDS/SUMER Prominence Observing Program I
A. Poland, B. Schmieder

First Draft  10/25/94
Revised 10/28/94
Revised 11/29/94
Amended 26 February 2004 with this attachment

Purpose:  To observe prominences on the limb with CDS and SUMER to determine
T, density, and v as a function of time in the prominence and surrounding
corona. An important aspect of this program, and a unique capability for
SOHO, is to observe the prominence material over a wide range of temperatures
to determine if observed visibility changes at one temperature are due to
density or temperature effects. A part of this question is does material in
small scale structure appear and disappear because of density or temperature

Another aspect is the material flow in small scale structures. Poland and
Mariska developed a syphon flow model for prominence development. This
observing program will help determine if the predicted velocity flows occur in
real prominences.

Observing Program:
1. In SUMER:   use the 1x300" slit.
               set the wavelength drive to 1390 to 1410A in KBr; 690-695, 705-
               710 bare 
               place slit 1' inside the limb to measure the photospheric line
               of S I at 1396.112A to get the "0" velocity wavelength      
               positioning(this will also compensate for solar rotation
               Make 1 observation with a long enough integration time to
               get a good line profile in the photosphere.
               Move SUMER to begin prominence observations.

2. In CDS:     Use the 90x240" slit, Make an observation with a 100 sec
               exposure showing the limb and as much of prominence as     
               Move the image 90" so the field of view is just above the      
               previous image and make another 100s exposure. This will give  
               us a good overall view of the prominence and surrounding corona
               over a wide temperature range.
               Use the following lines in VDS: MgVIII 317, FeXIII 320, FeXIV
               334, SiIX 341&345, MgIX 368, HeI 522, OIII 525, HeI 537, OIV
               553&554, NeVI 562, HeI 584, OIII 599, HeII 304(2), MgX 624, and
               OV 629.

            Integration time is estimated at 100s/image
            Windows need to be selected for 17 lines and 45 pixels/line in the
            wavelength direction and 120 pixels/line in the spatial direction
            for a total of 91,800 pixels/image(16bits/pix). This is
            14.688Kbits/sec., so we need some data compression to accommodate
            the rate of 10Kbits/sec.

            When this set of observations is complete (200s) change the slit
          to the 4x240" slit. Use the same lines as above but reduce each
          window to only 10 pixels/line in the wavelength direction. Each
          image is made with 100sec integration time. No compression is
          needed. After each image move the slit up 4". Repeat this 30 times
          for  120" coverage of the prominence and surrounding corona. This
          will take approximately 50 minutes. Repeat as time allows.  

3. In SUMER: Use the same slit and wavelength as in 1.
          Send lines: (KBr) SiIV 1393, OIV 1399&1401, SiIV 1402, O IV 1404,
          OIV  1407, and OIII 703(2): (Bare) NIII 685. Use 25 pixels in
          wavelength direction, 360 pixels in position direction. This means
          72,000 pixels or 720 pixels/sec or 11.5Kbits/sec. With overhead
          this means we should use a compression such as a moderate log.
          Make observations starting at the lowest position in the CDS
          observation. Integrate at each location for 100sec. After the
          first location move up 4" in synchronization with CDS if possible.
          This would skip data on 3" between each image.

4. Options:
     Examination of data indicates a change in the pointing scheme. For
     example, some dynamic activity in a small area needs further study.
     Same set of lines as in 2 and 3.  Since we are looking at dynamics we    
     will try a shorter integration time ("m" - try m=30 sec for a test) with 
     the loss of faint lines.
    SUMER  slit :1" X 300" (try sending only a limited area defined by "n"    
     where  n = 40" - this would mean a 40"x40" area)
     Still use the step in 3 of 4" and repeat it over an "n" ( 40") area with
     "m"sec integrations but with a repointing offset of 1 arcsec after       
     n/4 (10) scans and a back return to the initial position after 4 cycles.
     A rapid survey of a region  n X n (40 X40 ") will be done in 
     m x n/4 (5) minutes
     A full image in 20 minutes.  The area "n" ( 40") and the time m have to  
     stay as a free parameter that we could choose according to the
     evolution time of the prominence.
    CDS will scan a similar area (n x n) with
      a slit 2 X 240 " with a step of 4 arc sec,  a repointing offset of
      1 arc sec after "n/4" ( 10) scans and come back after
     4 cycles.  

  The observing parameters are consistent with the currently known
characteristics of CDS and SUMER. The onboard software may not allow the exact
procedures to be followed, but that is under current development. These
observing parameters still need to be run through the commanding tools to
generate instrument commands.

Coordination with the other instruments on SOHO:

UVCS - nothing specified - nearby coronal observations would be useful
EIT - images in the EIT observed bands would be useful.
The EIT will provide an overview of the prominence area and limb environment
with images in each of four bands. A successive acquisition of the full
disk images followed by sequences of 8X* arc min field of
view centered on the Field of view of SUMER may be convenient.

LASCO - nothing specified - nearby coronal observations would be useful

Ground based observatories during the european daylight time: 
MSDP (Meudon, Pic , Tenerife) Halpha  (Mein, Schmieder,Roudier)
coronographs: PICO, HACO (Halpha), IR coro Fe XIII.(NOens)
THEMIS (after 1996 in MSDP mode with 2 lines)
coronographs of  Wroclaw H alpha (Rompolt)
to have the survey of the neutral line along which lies
 the prominence: 
Huairou (Beijing- Dr Ai)
POtsdam (Germany, Dr. Hofman)
MEES (Hawaii) and MSFC (Hagyard)