SOHO Joint Observing Plan 017: Dynamics of Solar Active Structures (DYNAC)


Contributors: P.Mein and B.Schmieder DASOP, Observatory of Paris, Meudon.



Scientific Justification


The aim of this program is to study the flow (steady and rapid variation) in
and around chromospheric structures in the transition zone and coronal lines.

SUMER     CIV  1548.202 A      (10 E5 K)
          CIV  1550.774 A 
          SiII 1533.432 A      (2x10E4 K)

or

          OVI 1037.613  A      (2x 10E5 K)
          OVI 1031.912  A             
          Ly betta 1025.722 A  (2x 10E4 K)


We need to observe a low temperature (2 x10E4 K) with both instruments CDS
 and SUMER to coalign the observations with chromospheric ground-based 
observations.


The steady flow in the enviroment of a prominence will allow us to answer
questions on formation mechanisms (Injection of chromospheric material
or condensation of coronal plasma). A Center to limb investigation may be 
relevant in this program. Rapid time variations of the velocities may be 
detected in small scale structures, eruptive filaments, surges, spicules.
We need a fast raster scanning over a large area.

We plan to observe in 2 phases:

Phase 1: We plan to cover 300 X 300 arcsec**2 with SUMER and 240X240 arcsec**2
by CDS.

Phase 2: We plan to cover 120 X120 arcsec**2 with SUMER and 120 X240 arcsec**2
with CDS. These new areas will be inside the previous larger rasters.
 A step of 4 X 1.5 arcsec will be selected and shifted by 1.5 arcsec
in each of the following 3 scans. After 4 successive rasters with 1.52 arcsec
shift we plan to come back to the initial position.

We plan to observe the magnetic field using the french-italian telescope
THEMIS in Tenerife and the chromospheric velocity
field with the MSDP spectrograph. Observations during the european day 
time are required.


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 active region
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)
Tenerife : Gregory, VTT, THEMIS (after 1996 in MSDP mode with 2 lines)
coronographs of  Wroclaw H alpha (Rompolt)
Radio telescope of Nancay
magnetographs:
-------------
Huairou (Beijing- Dr Ai)
Potsdam (Germany, Dr. Hofman)
Tenerife THEMIS
MEES (Hawaii) and MSFC (Hagyard)







Operation Sequence


Phase 1: Reference image



Initial pointing                      Active region
Slit                                  1 X 300 arcsec**2
Scan area                             300 X 300 arcsec**2
Lines                                 C IV and Si II 
Step Size (half, full or              1.52 arcsec
          multiple steps)
Resulting Number of Scan Locations    200
Dwell time                            4 s (due to no storage on board)
Duration of Scan                      13 min 20 s (800 s)
Number of Mirror Settings             1 
Repointing                             none
Total duration                        13 min 20 s
Data Selection                        3 X intensity and centroid
storage requirements                  none 



Phase 2 : Observation


Initial pointing                      Selected after inspection of reference image
Slit                                  1 X 120 arcsec**2
Scan area                             120 X 120 arcsec**2
Lines                                 C IV and Si II 
Step Size (half, full or              4 X 1.52 arcsec
          multiple steps)
Resulting Number of Scan Locations    20
Dwell time                            4 s (taking into account the transmission time)
Duration of Scan                      80s + back
Number of Mirror Settings             1 
Repointing                             n X 1.52 (1< n<4)
Number of scans                       20 X 4
Total duration                        80 s X 4 X m (m number of cycles) =53 min for  image
Data Selection                        3 X intensity and centroid ( line width)
storage requirements                  none 
Co-operation Requirements             CDS    





For Phases 2 we have to define or predefine the new pointing startby using:
predefined coordinates
flag of largest velocities
flag brigthest point.
 
----------
For CDS


Initial pointing                      Pre-planned
Spectrometer                          Normal incidence
Slit                                  2 X 240 arcsec**2
Raster area                           Phase 1   240 X 240 arcsec**2
                                      Phase 2   120 X 240 arcsec**2
Raster Locations                      Phase 1 : 120
                                      Phase 2: 20 locations, 6 arcsec step
                                      consecutive rasters offset by 2 arcsec
                                      until 3 rd returns to start. 
Dwell time                            10 s (11.1 s)
Number of Rasters                     Phase 1: 1 Phase 2 : 3 X m
Reponiting                            none 
Duration of Raster                    Phase 1: 20 min     Phase 2: 200 s X 3 = 10 min
Total duration                        120 min
Line  selection                       He I 584, OV 629, Mg X 625
                                      Si IX 342, Si IX 349 (why not 345?)
                                      Mg IX 368   
Bins Across line                      21 (may be 15)

Co-operation Requirements             SUMER


To reduce the time of each raster of phase 2 we could read only 120
pixels and not 240.

The  Phases 1 with Sumer and CDS  may be lasted similar times.

For Phases 2 we have to define or predefine the new pointing start.