SOHO Joint Observing Programme 18 - CDS/MDI/SUMER/TRACE/NSO
   
   Sunspot Velocity Field in the Transition Region and Corona
   P. Maltby, O. Kjeldseth-Moe, ITA, University of Oslo
   R.A. Shine, Lockheed Palo Alto Research Laboratory
   T. Rimmele, National Solar Observatory (Sacramento Peak)

This updated SOHO JOP018, includes co-observations with TRACE. It 
is based on information obtained previously with this JOP and from
coordinated campaigns with CDS, MDI and observations from the 
ground. So far, intensity and line shift information has been 
obtained for 19 different sunspot regions in lines ranging in 
formation temperature from the chromosphere, through the transition 
region into the corona. We find that:

  - Regions with enhanced EUV emission and regions with strong 
    flows are distributed non-uniformly over the sunspot regions.

  - Regions with high intensity tend to be red shifted, but 
    seldom coincide exactly with enhanced velocity.

  - Sunspot plumes, i.e. regions above sunspots with intensity 
    larger than five times the average intensity in the CDS field 
    of view (FOV), are seen in 2/3 of the observed sunspot regions.

  - EUV spectral lines from the transition region are red-shifted 
    in sunspot plumes. 

Preliminary studies of the CDS/MDI campaigns promise to give further
interesting results.

TRACE observations are needed in this programme for two reasons:

  - To give images that are simultaneous over the field of view 
    and show the structure of the sunspot active region with high 
    angular resolution.

  - To map the time variation of the EUV emission in the features 
    occurring in the FOV of CDS and SUMER.

So far, available information on time variations have been limited to
studies with CDS using the view-finder mode, 90"x240" FOV, in three
lines, He I 584 A, O V 629 A, and Mg IX 338 A, taken with a cadence 
of more than 30 seconds. However, this mode of CDS is no longer used 
in active regions owing to the risk of damaging the detector by 
accidentally observing a solar flare. TRACE studies could:

    a) replace and strongly improve the spatial resolution of 
       active region images (TRACE has 1" angular resolution 
       as compared to 4" for CDS),
 
    b) obtain time series with a similar cadence as the CDS 
       view-finder mode,

    c) extend these observations to include three coronal lines, 
       Fe IX-X 171 A, Fe XII 195 A, and Fe XV 284 A, formed at 
       1.3 MK, 1.6 MK and 2 MK, respectively; one line from the 
       low transition region, C IV 1548 formed at 100 000 K;
       Lyman alpha, and white light "continuum".

Thus TRACE adds greatly to the scientific value of the programme 
and improves considerably on the old CDS observing mode that is 
no longer available. Combined CDS and TRACE observations improve
our knowledge of the fine structure and the corresponding time,
variation, which is furthermore likely to be related to the 
dynamical state of the solar atmosphere.

During the periods when SUMER is observing, coordinated observations
with TRACE may give improved knowledge of regions where SUMER lines
show complicated line profiles, such as explosive events and multiple
flows.



Details of the observing programmes
===================================

Contributions from the various instruments includes:

CDS:   runs the observing sequences o_spot2 and o_spot3. o_spot2 
       is a raster in 10 spectral lines covering the full range 
       in temperature from the chromosphere (He I lines) through 
       the transition region range up to 1 MK (O III, O IV, O V, 
       Ne VI, Mg VIII, Mg IX) and into the hot AR corona (Fe XIV,
       Fe XVI). Slit width is 2", and raster image size is 
       120"x120". The cadence is approximately 25 minutes. 
       o_spot2 is the basic CDS raster in the programme.

       o_spot3 is used only to give a quick map in 5 minutes in 
       the lines from O IV, O V, and Mg IX. This sequence is run
       only a few times during an observing session.

SUMER: cannot raster anymore. Instead we place the slit in the 
       CDS FOV and let the sunspot active region drift underneath
       while making exposures. The main part of the programme is
       exposures in a wavelength region containing the N V lines
       at 1238.82 A and 1242.80 A, and the O V line at 629.73 A.
       Corresponding rear slit camera images in white light are 
       recorded before and after these exposures, in addition to 
       wavelength calibration exposures, with long exposure times.
       A single exposure with long exposure time of the 1400 A 
       region, covering lines from Si IV, O IV and S IV, is also
       taken. SUMER may only be used in limited, designated 
       periods. 

MDI:   takes magnetograms in its high resolution mode, with good
       cadence, whenever the spot is inside the high resolution 
       FOV. Outside this area we can use available full disk 
       magnetograms,

TRACE: takes high cadence images in the various lines listed above, 
       in an area including the CDS FOV.

NSO:   studies the velocity field in the photosphere and chromo-
       sphere and takes white light images of the sunspot region.