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.